Cooper Creek under pressure: how climate change is reshaping an iconic desert river - Lethal Heating Editor BDA

Key Points

Cooper Creek is one of Australia’s longest inland river systems, stretching more than 1400 kilometres from Queensland into South Australia and feeding the Lake Eyre Basin.1 Its “boom and bust” hydrology supports vast wetlands, waterbird colonies and permanent waterholes that act as drought refuges for fish and other wildlife.2 Climate change is increasing temperatures and evaporation, reducing the persistence of waterholes and altering the timing and extent of floods.3 Water is allocated mainly to stock and domestic use, with limited irrigation, while environmental flows remain largely unregulated but vulnerable to future extraction.4 Existing water‑sharing plans aim to protect natural flow variability and connectivity between waterholes, yet climate‑driven drying threatens long‑term water security.5 Future basin management must prioritise protecting permanent refuges, minimising new infrastructure on flood paths, and integrating Indigenous knowledge into drought‑resilience planning.6

Cooper Creek snakes across some of the driest country on Earth, yet it pulses with life when floods arrive from the north. ¹

Stretching more than 1400 kilometres from central Queensland into northern South Australia, it is one of the continent’s longest inland river systems and a critical artery of the Lake Eyre Basin. ¹

For thousands of years Aboriginal people have relied on its waterholes, floodplains and trade routes, embedding the creek deep in cultural memory. ¹¹

Today it also sustains pastoral stations, small towns, tourism and a globally significant network of wetlands that host millions of waterbirds in big flood years. ²

Climate change is now altering the rhythm of these floods, lengthening droughts and threatening the delicate balance between people, livestock and wildlife. ³

Water‑sharing rules, built around highly variable natural flows, face mounting pressure as temperatures rise and evaporation soaks up more of the system’s limited water. ⁵

How Cooper Creek is managed over the coming decades will determine whether it remains a resilient desert lifeline or becomes another river system stressed beyond its limits. ⁶

Geography and physical character

Cooper Creek begins in the Channel Country of western Queensland, fed by tributaries such as the Barcoo and Thomson rivers that carry monsoonal rains from the north and east. ¹

From there it meanders southwest across low‑gradient plains, eventually crossing into South Australia and feeding the Kati Thanda–Lake Eyre terminal basin. ¹

The total catchment covers more than 29 million hectares, making it one of the largest unregulated river systems in Australia. ²

Across much of its length the creek is ephemeral, with long stretches dry for years at a time and only a few permanent or near‑permanent waterholes. ²

When floods arrive, water spreads across wide, shallow channels and swamps, creating a braided network of flows that can take weeks or months to move through the system. ²

Geomorphological studies show that sand dunes, alluvial fans and low‑relief plains shape how floodwaters move, with lakes and swamps acting as “sinks” that slow and store water. ²

This slow, diffuse flow regime is what allows wetlands such as the Coongie Lakes to fill and support huge populations of waterbirds and native fish. ²

Economic, ecological and cultural importance

Ecologically, Cooper Creek is an international reference site for how intermittent desert rivers function. ²

Its “boom and bust” cycles drive explosive growth in aquatic plants, fish and invertebrates during floods, followed by a contraction into deep, permanent waterholes that sustain species through drought. ²

The Coongie Lakes in South Australia are listed under the Ramsar Convention for their global importance to waterbirds, with surveys recording up to several million birds in major flood events. ²

Permanent refuges such as Cullyamurra and Nappa Merrie waterholes shelter at least 13 native fish species and other aquatic fauna when the wider system dries. ²

Economically, the creek underpins extensive pastoral leases where cattle graze on natural floodplain pastures after big rains. ²

Oil and gas operations in the Cooper Basin draw on groundwater resources linked to the same basin, while tourism around Innamincka and the Channel Country relies on the river’s dramatic floods and wildlife. ²

Culturally, Cooper Creek has been a trade and travel corridor for Aboriginal groups for tens of thousands of years, with sites along its banks marking meeting places, ceremonial grounds and resource‑rich refuges. ¹¹

Climate change and the shifting hydrology

Climate projections for the Lake Eyre Basin indicate rising temperatures, higher evaporation and more erratic rainfall, all of which affect Cooper Creek’s flow patterns. ³

Mean annual pan evaporation in the South Australian section already exceeds 3500 millimetres, far outstripping the region’s median rainfall of about 100–150 millimetres. ²

Hydrological modelling suggests that even modest reductions in flow or increases in evaporation can shorten the time waterholes remain full, shrinking the number of drought refuges. ³

Studies of similar arid‑zone waterholes show that higher temperatures and evaporation are likely to reduce waterhole persistence, making native fish and other aquatic species more vulnerable. ¹⁹

At the same time, climate models indicate that when rain does fall it may come in more intense bursts, potentially leading to larger but less frequent floods that can alter sediment and vegetation patterns. ³

These changes threaten the finely tuned “boom and bust” ecology that many plants and animals depend on, including waterbirds whose breeding is tightly linked to flood timing and extent. ²

Water allocation and use

Water in the Cooper Creek system is governed by state‑based water‑sharing plans that distinguish between surface water, overland flows and groundwater. ⁴

In Queensland, the Water Plan (Cooper Creek) 2011 defines availability, sets rules for taking water and seeks to maintain the variability and seasonality of natural flows. ⁵

Most surface‑water entitlements are for stock and domestic use, with only small‑scale irrigation occurring in the upper catchment and limited infrastructure such as weirs or dams. ⁵

In South Australia, the Cooper Creek Water Allocation Plan similarly prioritises existing stock and domestic needs while recognising the ecological value of unregulated flows. ¹⁷

Environmental water is largely implicit in the system’s natural variability rather than allocated through formal “environmental entitlements”, because the river remains largely unregulated. ²

Urban and industrial uses are minor compared with pastoral demands, though growing mining and tourism activity increase pressure on local groundwater and surface‑water access points. ²

Climate change and future water security

As climate change reduces the reliability of floods and lengthens dry periods, the same water‑sharing frameworks that once assumed highly variable but broadly stable flow regimes now face a different reality. ³

Existing plans emphasise maintaining connectivity between waterholes and avoiding significant extraction from permanent refuges, but they were not designed for a consistently hotter, drier climate. ⁵

Higher evaporation and reduced flow persistence could shrink the pool of water available for stock, domestic use and environmental function, particularly in the lower Cooper where water already becomes saline in prolonged droughts. ²

Any expansion of irrigation or new large‑scale extractions would further stress the system, especially if they occur in parts of the catchment that currently provide critical flood pulses downstream. ⁵

Infrastructure such as raised roads, bridges and mine access tracks can also disrupt natural flow paths, changing where and how floodwaters spread and potentially isolating wetlands and waterholes. ²

Indigenous and local knowledge, combined with hydrological monitoring, will be essential to detect early signs of change and adjust management before key refuges are compromised. ¹¹

What planners and policymakers must focus on

To safeguard Cooper Creek, regional planners and policymakers must treat permanent waterholes and key wetlands as non‑negotiable ecological assets, restricting any new extraction that would reduce their reliability. ²

Water‑sharing rules should be periodically reviewed against updated climate projections and hydrological data, with explicit triggers for tighter extraction limits during extended droughts. ³

New infrastructure on flood paths, including roads, bridges and mining facilities, must be designed to allow natural flow patterns and avoid fragmenting the system’s connectivity. ²

Integrated groundwater‑surface water management is needed to prevent over‑reliance on bores that could deplete aquifers linked to the river’s refuges. ⁵

Finally, formalising the role of Aboriginal knowledge and local pastoral experience in drought‑planning and monitoring will strengthen the evidence base for decisions that affect both people and ecosystems. ¹¹

If these steps are taken, Cooper Creek can continue to function as a resilient desert river, even as climate change reshapes the arid landscapes it flows through. ⁶

References

1. Cooper Creek | Research Starters – EBSCO
2. Managing the High Ecological Value Aquatic Ecosystems – SAAL
3. Climate Change Impacts on the Water Resources of the Cooper Creek Catchment – MODSIM
4. Cooper Creek water resource planning area – WetlandInfo
5. Water Plan (Cooper Creek) 2011 – Queensland Legislation
6. Innamincka/Cooper Creek State Heritage Area – SA Environment
7. Water Resource (Cooper Creek) Plan 2011 – Queensland Legislation
8. Climate change effects on waterhole persistence in rivers – ScienceDirect
9. Water Sharing Plan for the Coopers Creek Water Source 2003 – NSW Legislation
10. Water Resource (Cooper Creek) Plan 2011 – Queensland Government
11. Innamincka/Cooper Creek State Heritage Area – SA Environment (Aboriginal heritage)
12. Cooper Creek – Wikipedia (contextual overview)

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When insurance becomes a climate faultline: how global heating is reshaping Australia’s safety net - Lethal Heating Editor BDA

Key Points

Extreme weather in 2025 caused about $3.5 billion in insured losses across Australia.1 Home insurance premiums have surged, with 1.24 million households now facing acute affordability stress.2 Climate change is driving heavier downpours, harsher fire weather and more intense tropical cyclones, increasing loss risks.3 A Senate inquiry has warned that some communities face uninsurability without stronger mitigation and planning reforms.4 Government schemes such as the cyclone reinsurance pool and Hazards Insurance Partnership aim to curb premiums in high‑risk areas.5 Insurers are reshaping products, data and capital to cope with mounting climate risk and guide adaptation.6

Insurance used to sit quietly in the background of Australian life, a renewal notice paid and forgotten, but climate change has pushed it to the centre of a national cost and security crisis.¹

In 2025 the Insurance Council of Australia (ICA) reported that extreme weather disasters generated nearly $3.5 billion in insured losses, from roughly 264,000 claims across the country.¹

That bill was driven by cyclones, floods and storms, led by Ex‑Tropical Cyclone Alfred in March, which alone accounted for more than $1.5 billion in insured losses and over 130,000 claims.¹

By mid‑2025 three declared disasters had already produced more than $1.8 billion in claims, underlining how quickly the climate‑charged damage tally is rising.²

As payouts escalate, premiums have surged, with new Actuaries Institute analysis showing average home insurance costs jumping 28 per cent in the year to March 2025, to $1,894, and the highest‑risk properties up by around 50 per cent.³

About 1.24 million households are now in “affordability stress”, spending roughly nine weeks of income on home insurance, concentrated in flood and cyclone‑exposed regions of northern Queensland, the Northern Territory and northern New South Wales.³

Behind these numbers sits a deeper structural faultline, as government, regulators and the industry grapple with the risk that entire postcodes – and eventually whole regions – could become functionally uninsurable in a warming world.³

Climate signals behind the loss surge

The escalation in losses is anchored in observed climate trends, not just bad luck from a run of wet or windy years.⁴

CSIRO’s latest State of the Climate findings show Australia has warmed by more than 1.4 degrees since 1910, with more frequent extreme heat and more intense short‑duration heavy rainfall events, even in regions where average rainfall is flat or falling.⁴

Those downpours drive flash flooding in cities and regional towns, overwhelming stormwater systems and inundating homes and businesses that were never mapped as high‑risk when they were built.⁴

Fire weather has become more severe with a longer fire season across much of southern and eastern Australia, compounding insurance exposure by stacking bushfire risk on top of flood and storm losses.⁴

CSIRO and the Bureau of Meteorology project that tropical cyclones may become less frequent overall but more intense on average, with higher rainfall rates and storm surges due to rising seas, which can produce higher loss events when they make landfall.⁴

This shift is already visible in claims data, with the ICA noting that Alfred’s 2025 deluge, and a series of East Coast storms and floods, fitted the pattern of slower‑moving, wetter systems delivering outsized damage over large catchments.¹

For insurers and reinsurers, the result is a step change in the expected frequency and severity of losses, forcing a rapid repricing of risk and raising hard questions about what remains insurable on commercial terms.¹

Premium pain and the edge of uninsurability

The human face of this repricing is a swelling cohort of households for whom comprehensive cover is either barely affordable or out of reach altogether.³

The Actuaries Institute’s 2025 home insurance affordability update estimates that 12 per cent of households – around one in eight – are now experiencing “extreme affordability pressure”, up from 10 per cent a year earlier.³

On average these households spend 8.8 weeks of their income on home insurance, but the burden is far higher in the most exposed riverine floodplains and cyclone belts, where premiums for some properties have doubled or more in recent years.³

Earlier modelling for the New South Wales Government highlighted that inland towns with combined flood exposure and lower incomes – including parts of the Northern Rivers and central west – are now hotspots for underinsurance and non‑insurance.⁵

The NSW climate risk analysis found vulnerable households in northern Queensland, the Northern Territory and northern New South Wales were disproportionately likely to face affordability problems, especially where old housing stock and inadequate mitigation compound climate hazards.⁵

Without intervention, the Actuaries Institute warns that climate change and shifting exposure could push many more properties into the highest‑risk, highest‑premium categories over coming decades, deepening what it calls an “insurance protection gap” between rich and poor communities.³

This raises the spectre of effective uninsurability, where cover technically exists but at prices far beyond the reach of average households, depressing property values and undermining access to finance in those areas.³

Senate inquiry: climate risk as a systemic threat

These pressures prompted the Senate in 2024 to establish a Select Committee on the Impact of Climate Risk on Insurance Premiums and Availability, tasked with examining whether parts of Australia are drifting towards an uninsurable future.⁶

The committee, which tabled its final report in November 2024, heard extensive evidence from disaster‑affected communities, consumer groups, industry and experts about the intersection of climate change, planning decisions and insurance markets.⁶

Submissions highlighted that insurance unaffordability is not confined to cyclone‑exposed northern coasts but is emerging across floodplains, bushfire‑prone peri‑urban fringes and erosion‑threatened coasts, where legacy planning rules allowed high‑risk development.⁷

The Housing Industry Association, for example, told the inquiry that governments must do more to retrofit existing homes for natural hazards and reconsider where rebuilding occurs after repeat disasters, rather than simply shifting costs to new home buyers.⁷

Actuarial evidence to the inquiry underscored that climate‑driven natural peril risks are a substantial and rising component of premiums, with the heaviest burden falling on a relatively small share of households in high‑risk locations.³

The committee’s report called for better data on insurance affordability and availability, targeted mitigation funding, and exploration of tools such as means‑tested subsidies or risk‑based stamp duty reform to ease pressure on low‑income households in high‑risk zones.⁶

Its findings sit alongside an Australian Prudential Regulation Authority (APRA) climate vulnerability assessment, which is building an affordability metric in “weeks of income” to track how climate and transition risks could reshape general insurance markets by 2050.⁸

Government interventions: reinsurance pools and partnerships

In response to mounting concern, federal policy has begun to move from crisis‑by‑crisis disaster relief towards more systematic efforts to stabilise premiums and reduce risk.⁹

Central to this is the cyclone reinsurance pool, operated by the Australian Reinsurance Pool Corporation (ARPC) and backed by a $10 billion government guarantee, which allows insurers to transfer cyclone and cyclone‑related flood risk to the public balance sheet.⁹

The pool covers household, strata and small business property policies nationwide but targets support to cyclone‑prone regions, and has been fully operational since January 2025, with all large insurers on board and smaller insurers joining in line with reinsurance renewals.¹⁰

Early data from Far North Queensland indicates that around 78 per cent of households hold home insurance, and ARPC plans to use the pool’s granular data to track coverage and affordability over time in high‑risk regions.¹⁰

Alongside the pool, the Albanese government has set up the Hazards Insurance Partnership (HIP), an enduring forum between government and major insurers, managed by the National Emergency Management Agency.¹¹

The partnership is designed to share data on natural hazard risk, co‑design mitigation priorities and provide transparent updates on measures to improve insurance affordability and availability in exposed communities.¹²

The 2024–25 federal budget also allocated additional funding to disaster resilience, including the Disaster Ready Fund and targeted resilience programs, which are intended to complement insurance measures by cutting physical risk rather than merely subsidising prices.¹³

Advocates argue that every dollar spent on risk‑reducing infrastructure, such as levees, buybacks, house raising or fire‑resistant retrofits, can save many times more in avoided disaster losses and help bring premiums back within reach over time.⁵

How insurers are adapting to a riskier climate

While governments adjust policy levers, insurers themselves are reshaping products, capital and data to live with a more volatile climate.¹⁴

KPMG’s 2025 general insurance insights report notes that strong growth in gross written premiums has been driven partly by higher rates reflecting worsening natural disaster risk, rising reinsurance costs and ongoing supply chain pressures in rebuilding and repairs.¹⁴

Insurers are experimenting with more granular risk‑based pricing, using improved flood and cyclone models, property‑level data and remote sensing to distinguish between homes on the same street with markedly different hazard profiles.¹⁴

Many insurers are also refining underwriting rules, tightening coverage in repeated‑loss locations, increasing excesses for some perils, or in some cases declining cover where they judge the risk as beyond tolerable bounds.¹⁴

At the same time, the industry is under pressure from regulators and investors to decarbonise its own portfolios, disclose exposure to climate risks, and support resilience measures that can reduce long‑term claims costs.⁸

Insurers are working with governments through HIP and other forums to link premium discounts to mitigation – for example, lowering premiums for homes elevated above projected flood levels, re‑roofed to cyclone standards or retrofitted with ember‑resistant features in bushfire zones.¹²

Industry action plans released in response to inquiries into the 2022 floods outline commitments to improve claims handling, invest in community engagement and support better land‑use planning so that future development avoids the worst hazards rather than locking in new pockets of high risk.¹⁴

What planners and policymakers must do next

Insurance is ultimately a signal, not a solution, and the signals from 2025’s loss data and 2026’s early disasters are stark.¹

To preserve insurance as a functioning safety net, regional planners and policymakers will need to focus on four core tasks: 

• Stop putting new assets in harm’s way, 
• Aggressively reduce risk to existing homes and infrastructure, 
• Target support to affordability‑stressed households in high‑risk areas, and 
• Align emissions cuts with adaptation so that today’s hazards do not become tomorrow’s uninsurable extremes.³

That means: 

• Tightening planning controls in floodplains, firegrounds and eroding coasts, 
• Accelerating buybacks and relocations in the most exposed pockets, and 
• Embedding resilience standards in building codes and retrofits at scale.⁷

It also requires: 

• Stable, long‑term funding for mitigation infrastructure, 
• Robust data on insurance availability and affordability, and 
• Social policies – from targeted subsidies to consumer protections – that ensure low‑income and regional households are not left without cover as climate risks rise.⁵

If those steps are taken, insurers can continue to pool and price risk, communities can rebuild with more confidence, and the country can avoid a slide into patchwork “insurance deserts” where the impacts of global heating are carved into the housing market as clearly as any flood line.³

References

1. Insurance Council of Australia data on 2025 extreme weather losses (via Artemis)
2. Insurance Council of Australia: Extreme weather losses in 2025 exceed $1.8 billion
3. Actuaries Institute: Home Insurance Affordability Update and Funding for Flood Costs (2025)
4. CSIRO State of the Climate 2024 – key findings summary
5. NSW Government: Rising climate risks – why accessible, affordable home insurance is under threat
6. Senate Select Committee on the Impact of Climate Risk on Insurance Premiums and Availability – Final Report (2024)
7. Housing Industry Association submission to Senate inquiry on climate risks and insurance premiums
8. APRA Insurance Climate Vulnerability Assessment – information paper (2024)
9. Australian Reinsurance Pool Corporation: The Cyclone Reinsurance Pool
10. Joint Committee on Northern Australia: Cyclone Reinsurance Pool inquiry – current situation (2025)
11. Minister for Emergency Management: Landmark partnership to improve disaster insurance
12. Hazards Insurance Partnership – Terms of Reference
13. Highlights of the 2024–25 Federal Budget and insurance implications
14. KPMG: General Insurance Insights & Analysis 2025

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Big water under pressure: how climate change is reshaping the Murrumbidgee River - Lethal Heating Editor BDA

Key Points

The Murrumbidgee River is a heavily regulated Murray–Darling tributary under growing climate stress 1 Irrigation and regional economies depend on shrinking, highly contested flows 2 River health is declining, with reduced flows, habitat loss and frequent algal blooms 3 Climate change is projected to bring hotter conditions and more variable rainfall in the Murray–Murrumbidgee region 4 Environmental water targets in the upper Murrumbidgee are often not met because of limited allocations 5 Future water security will hinge on tougher allocation decisions, better governance and climate‑ready adaptation plans 6

The Murrumbidgee River is a lifeline for south‑eastern Australia, yet its future is being rewritten by a hotter, drier climate.

From its snow‑fed headwaters in the Australian Alps to its junction with the Murray River, this long, regulated system underpins city water supplies, high‑value irrigation, wetlands and First Nations cultures.

Over recent decades, climate change, river regulation and intensive extraction have combined to steadily erode flows, squeeze environmental water and increase pressure on river communities.

Scientists now warn that further warming will likely deepen these trends, sharpening trade‑offs between food production, town water security and the survival of already stressed ecosystems.¹⁴

In the Murrumbidgee this is not an abstract risk but a lived reality, visible in shrinking floods, rising salinity, recurring blue‑green algal blooms and wetlands that no longer fill as often or as long as they once did.¹

At the same time, the river remains central to a regional economy worth billions of dollars a year and to the identity of communities that have grown up along its banks.²

How governments, Basin authorities, Traditional Owners and local communities respond over the next decade will shape whether the Murrumbidgee can remain a working river that still supports healthy ecosystems in a rapidly changing climate.¹⁶

Big water: scale, seasons and regulation

Running for around 1,485 kilometres from the Snowy Mountains to the Murray, the Murrumbidgee drains a catchment of about 84,000 square kilometres and is one of the largest tributaries in the Murray–Darling Basin.⁷

The river’s name, from the Wiradjuri language, is often translated as “big water” or “overflowing”, reflecting the way it once spread across floodplains and wetlands during natural high flows.¹⁰

Today the system is classed as one of Australia’s most regulated rivers, with at least 26 major storage or diversion structures, including Tantangara, Burrinjuck and Blowering dams, weirs and extensive irrigation channels.¹

These storages smooth out natural flow peaks, capture snowmelt and rainfall, and divert large volumes for irrigation or into neighbouring basins through schemes such as the Snowy Hydro transfers.¹¹

In the upper Murrumbidgee, research shows that on average about 93 per cent of annual flow can be diverted at Tantangara Dam in some years, leaving only a small fraction to move downstream as planned environmental or base flows.¹¹

Further downstream, the river spreads into the mid‑Murrumbidgee and Lowbidgee floodplains, which once supported extensive red gum forests and wetlands but now receive far fewer and shorter floods because of both water extraction and a drying climate.¹⁶

This combination of infrastructure, inter‑basin transfers and climate‑driven drying underpins many of the river’s current challenges, from declining wetland health to heightened competition between users in dry years.²⁰

The Murrumbidgee valley is recognised by New South Wales authorities as one of the state’s most heavily regulated systems, which makes managing water for the environment particularly complex as conditions change.¹

River of food, culture and country

More than half a million people live in the wider Murrumbidgee catchment, including the regional cities of Canberra, Wagga Wagga and Griffith, along with dozens of irrigation towns and rural communities.⁷

The river crosses the Traditional lands of First Nations including the Ngambri, Ngunnawal, Wiradjuri and other groups, for whom its waters, fisheries and floodplains have long been central to culture, trade and story, as well as to spiritual responsibilities for Country.¹⁰

Economically, the Murrumbidgee Irrigation Area and surrounding districts form one of Australia’s most productive farming regions, with about 120,000 hectares irrigated annually across crops such as rice, cotton, nuts, grapes, citrus and vegetables.⁵

Studies estimate that the gross value of farm production in the irrigation area alone is in the order of hundreds of millions of dollars each year, with broader value chains for rice, horticulture and livestock lifting the regional economic contribution into the billions.²

At the same time, Canberra and other communities rely on the Murrumbidgee and its storages for drinking water, while tourism, recreation and cultural activities are tightly linked to the river’s flows and water quality.⁴

Environmental assets such as the mid‑Murrumbidgee and Lowbidgee wetlands are nationally significant habitats, supporting waterbird breeding and threatened species like the southern bell frog when they receive adequate flooding.¹³

These overlapping economic, cultural and ecological values mean that any decline in river health or reliability reverberates quickly through communities, industries and ecosystems.¹⁸

Analyses of water use in the catchment show that the value of irrigation water is high, underscoring how strongly regional livelihoods and export industries are exposed to changes in allocations and long‑term flow trends.⁸

Climate change: a drying, hotter future

Evidence is mounting that climate change is already reshaping the Murrumbidgee’s flow regime, with studies documenting significant declines in wet‑season river heights since the 1990s and increasingly frequent years of low inflow.¹³

An analysis published in 2021 linked these trends directly to reduced rainfall driven by global warming, warning that the catchment’s economic, social and ecological viability is at risk under ongoing drying.¹³

Regional climate projections for the Murray–Murrumbidgee show temperatures rising by around 0.7 degrees in the near term and close to 2 degrees by the latter half of the century, with more hot days and fewer cold nights.¹⁴

Rainfall is projected to become more variable, with likely decreases in spring, possible increases in some summer and autumn periods, and an overall higher risk of lower median inflows in key catchments such as the Murrumbidgee.¹⁶

National assessments of Australia’s changing climate also point to a trend towards more intense downpours when rain does fall, which can increase flood risks even as average conditions become drier and evaporative demand rises.¹⁷

For the river, this means longer dry spells, hotter summers that boost evaporation and water demand, and more erratic but sometimes heavier rainfall events that challenge existing dams, weirs and levees.²⁰

Scientists studying the Lowbidgee floodplain have concluded that both river regulation and climate change are now working together to reduce the frequency and extent of floods, undermining the ecological character of wetlands and forest systems.²⁰

New South Wales climate snapshots for the Murray–Murrumbidgee region emphasise that all key temperature measures are expected to rise and that climate change will intensify fire weather, heatwaves and water stress across the basin.¹⁴

Water allocation, quality and river health

Water in the Murrumbidgee is allocated through a complex mix of state water‑sharing plans, Murray–Darling Basin Plan settings and specific rules for urban supply, irrigation licences and environmental entitlements.¹⁵

In most years agriculture remains the largest consumptive user, ahead of town water, industry and stock, although many irrigators now hold a mix of high‑ and general‑security entitlements and participate in water trading to manage risk.⁸

The Basin Plan has seen substantial volumes of water recovered for the environment across the Murray–Darling, with more than 2,100 gigalitres of entitlements secured by 2020, including significant holdings in the Murrumbidgee to support regulated environmental flows and targeted floodplain watering.¹⁵

Despite this, recent research into the upper Murrumbidgee found that annual environmental release targets of 27 gigalitres were not met in two‑thirds of years from 2008 to 2022, largely because allocations to environmental accounts were constrained during dry conditions.¹¹

The same work highlighted that in some years up to 99 per cent of the upper river’s natural flow is diverted at Tantangara, contributing to poorer habitat, sediment build‑up, declining native fish populations and lower water quality downstream.¹¹

Further along the valley, Commonwealth environmental water has been used to deliver strategic pulses and base flows to support key wetlands, fish habitat and waterbird breeding, but managers report that meeting ecological objectives is increasingly difficult in a warming climate with tighter water constraints.¹⁸

Low flows, high temperatures and elevated nutrient loads have also contributed to recurring outbreaks of blue‑green algal blooms in lakes and river reaches linked to the Murrumbidgee system, with warnings issued for recreational and stock water use in areas such as Lake Wyangan and ACT lakes that drain to the river.³

Authorities note that the slow‑moving nature of regulated rivers, combined with drought and nutrient‑rich runoff, creates ideal conditions for algal blooms that reduce water quality, harm aquatic life and disrupt irrigation and tourism.⁶

The pattern of under‑delivery against environmental flow targets in the upper river has prompted calls for more enforceable rules, better outlet capacity at key dams and a re‑examination of how inter‑basin transfers interact with downstream ecological needs.¹²

Securing the Murrumbidgee in a hotter century

Climate change means the Murrumbidgee can no longer be managed on the assumption that past river behaviour will guide the future, forcing planners to confront more frequent water shortages and sharper trade‑offs between users.¹³

State adaptation programs already identify the Riverina‑Murray as highly exposed to climate impacts, pointing to the need for councils, governments and communities to factor lower inflows and more extreme events into infrastructure, land‑use and water‑security planning.¹⁶

Hydrological modelling suggests that without stronger action to reduce emissions globally and adapt locally, river flows to key floodplains could decline further, intensifying stress on wetlands, forests and the species that depend on them.²⁰

For irrigated agriculture, this will likely mean continuing pressure to upgrade on‑farm efficiency, shift to crops that can tolerate higher water prices and variable supply, and use water markets to move scarce water to higher‑value uses.⁸

Community‑led restoration projects along the Murrumbidgee, including habitat works, native revegetation and invasive species control, show how local groups can build ecological resilience even as large‑scale pressures mount.¹⁹

However, experts stress that such efforts must sit alongside reforms to river operations, environmental water delivery and land management, so that limited flows can be used more strategically to support both communities and ecosystems.

In the coming decades, the central task for policymakers will be to align water‑sharing rules, Basin Plan commitments and climate policy so that the river’s working role is preserved without sacrificing the environmental foundations that underpin long‑term regional prosperity.¹⁵

That will require clearer climate‑adjusted limits on extraction, stronger protection for environmental and cultural flows, and stable, long‑term investment in adaptation so that communities along the Murrumbidgee are not left to carry the risks of a hotter, drier basin alone.¹⁶

References

1. NSW Department of Climate Change, Energy, the Environment and Water – Murrumbidgee valley: Water for the environment
2. ACCC – Murrumbidgee Irrigation submission: Economic contribution of the Murrumbidgee Irrigation Area
3. Griffith City Council – Lake Wyangan water quality and algal blooms
4. Icon Water – Murrumbidgee River drinking water sources
5. Charles Sturt University – Irrigation in the Murrumbidgee Irrigation Area
6. ACT Government – Algal blooms in Canberra lakes and waterways
7. The Murrumbidgee – River region facts
8. Qureshi et al. – An empirical assessment of the value of irrigation water in the Murrumbidgee catchment
9. Encyclopaedia Britannica – Murrumbidgee River overview
10. McGuire et al. 2025 – Environmental flows in the upper Murrumbidgee River
11. NSW Water – Adequacy of environmental releases to the upper Murrumbidgee River
12. The Conversation – The Murrumbidgee River’s wet season height has dropped by 30% since the 1990s
13. NSW Government – Murray Murrumbidgee climate change snapshot
14. Wentworth Group of Concerned Scientists – Assessment of river flows in the Murray–Darling Basin
15. AdaptNSW – Climate change in the Riverina Murray
16. CSIRO/Bureau of Meteorology – Australia’s changing climate
17. Commonwealth Environmental Water Holder – Murrumbidgee 2019–20 monitoring and evaluation technical report
18. Murrumbidgee Landcare – Supporting the Murrumbidgee River: collaborative habitat restoration
19. Kreibich et al. 2024 – River regulation and climate change reduce river flows to the semi‑arid Lowbidgee floodplain

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The Darling River Under Pressure: Climate Change, Water Extraction and the Fight for Australia’s Inland Lifeline - Lethal Heating Editor BDA

Key Points

The Darling River is one of Australia’s longest inland rivers and a central artery of the Murray-Darling Basin.1 The river supports agriculture, towns, ecosystems and cultural connections across multiple States.2 Water allocation is governed by the Murray-Darling Basin Plan and sustainable diversion limits.3 Climate change and historical extraction have increased flow variability and water stress.2 Environmental water has improved some ecosystems, but many wetlands and species remain at risk.4 First Nations cultures and regional economies are deeply dependent on river health and fair governance.1

The Darling River runs through the heart of inland Australia, sustaining life, culture, and economies in landscapes increasingly shaped by climate change. ¹

Flowing more than 1,400 kilometres from northern New South Wales to its junction with the Murray River at Wentworth, the Darling River forms a critical backbone of the Murray-Darling Basin, Australia’s largest and most economically significant river system. ¹

The river sustains regional towns, irrigated agriculture, floodplain wetlands and deep cultural connections that stretch back tens of thousands of years, making it far more than a channel of moving water. ¹

Yet the Darling has also become one of the most contested and vulnerable rivers in the country, exposed to intensifying climate extremes and the cumulative impacts of decades of water extraction. ²

Geography and scale of the Darling River

The Darling River drains a vast inland catchment characterised by highly variable rainfall, long dry periods and episodic flooding that historically shaped the ecology of the river and its floodplains. ¹

As a major tributary of the Murray River, it contributes to a connected basin spanning roughly one million square kilometres across Queensland, New South Wales, Victoria and South Australia. ²

This basin supports around forty percent of Australia’s agricultural production by value, underlining the national importance of the Darling’s flows even though the river itself passes through sparsely populated regions. ²

Natural flow variability has always defined the river, but recent decades have brought longer droughts and more intense floods that exceed historical experience. ²

Water allocation and use

Water from the Darling is allocated under the Murray-Darling Basin Plan, a legislated framework designed to limit total extraction and return water to rivers and wetlands for ecological health. ³

Sustainable diversion limits cap how much water can be taken for irrigation, towns and industry, with allocations adjusted according to seasonal conditions and storage levels. ³

Irrigated agriculture along the Darling includes cotton, cereals, fodder and horticulture, supporting regional employment and export income but also creating strong competition for limited water. ²

Water trading allows entitlements to move between users, improving economic efficiency but also raising concerns about concentration of ownership and impacts on local communities. ³

Ecological and cultural importance

The Darling River supports extensive floodplain forests, wetlands, and anabranches that provide habitat for native fish, waterbirds, and invertebrates. ⁴

Many species depend on periodic flooding to trigger breeding and maintain food webs, making flow timing and connectivity as important as total volume. ⁴

For Aboriginal Nations across the basin, the river is a living cultural entity central to law, identity and intergenerational knowledge. ¹

Degraded flows and declining water quality disrupt cultural practices, reduce access to traditional foods and erode cultural landscapes. ¹

Climate change, flows and water quality

Climate change is increasing temperatures across the basin, intensifying evaporation and reducing runoff even when rainfall totals remain similar. ²

Research shows that climate driven declines in cool season rainfall are likely to reduce average river flows while increasing year to year variability. ²

Lower flows concentrate salts and nutrients, increasing the risk of algal blooms, fish kills and water supply failures for towns. ²

These risks are magnified when climate pressures interact with upstream extraction and floodplain harvesting. ²

Communities and economies dependent on the river

Towns along the Darling rely on the river for drinking water, industry, schools and basic services, making flow reliability a public health issue. ¹

During prolonged droughts, some communities have required emergency water supplies as river pools shrink or become too saline to treat. ²

Tourism, fishing, and recreation also depend on healthy river conditions and contribute to local incomes when flows are adequate. ⁴

Policy responses and future directions

Governments and the Murray-Darling Basin Authority regularly review the Basin Plan to respond to new science, climate projections and social impacts. ³

Environmental water holders seek to deliver targeted flows that improve resilience, reconnect wetlands and support native species breeding. ⁴

The long term future of the Darling River depends on transparent governance, strong compliance and adaptation to a hotter and more variable climate. ²

References

• NSW Government. Darling River system overview and regional river health profile
• CSIRO and DCCEEW. Climate change impacts on water availability in the Murray-Darling Basin
• Murray-Darling Basin Authority. Basin Plan water allocation framework and sustainable diversion limits
• Government of South Australia. Environmental water management and ecological outcomes
• Australian Government DCCEEW. Murray-Darling Basin Plan policy settings and reforms
• Bureau of Meteorology. Observed and projected climate change across Australia
• Murray-Darling Basin Authority. Environmental water delivery and monitoring
• Productivity Commission. Review of the Murray-Darling Basin Plan implementation
• Australian Institute of Health and Welfare. Water resources, ecosystems and community wellbeing
• Australian Institute of Aboriginal and Torres Strait Islander Studies. Indigenous connections to water and Country

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The River Murray at a crossroads in a hotter, drier Australia - Lethal Heating Editor BDA

Key Points

The River Murray runs for more than 2,500 kilometres across three eastern states and the ACT, draining a vast semi-arid basin.[1] The river underpins billions of dollars in irrigated agriculture and supplies drinking water to major inland cities and regional towns.[2] Climate change is driving declining streamflows, hotter conditions and more frequent extremes, tightening water security for communities and ecosystems.[3] Traditional Owners along Murrundi hold deep cultural, spiritual and economic connections to the river and are seeking greater say over water.[4] The Murray–Darling Basin Plan has recovered water for the environment, but many wetlands, floodplains and the Coorong still show signs of stress.[5] Climate adaptation will demand tougher trade-offs, smarter environmental watering and stronger inclusion of First Nations water knowledge.[6]

The River Murray is flowing under growing climate strain, and what happens to its water will shape the future of inland south-eastern Australia.^[3]

Stretching across Queensland, New South Wales, the Australian Capital Territory, Victoria and South Australia, it anchors the wider Murray–Darling Basin, which covers about one seventh of the continent.^[1]

More than two million people rely directly on Murray water for drinking, farming and industry, while many more depend on basin food and fibre exports.^[2]

The river is also central to the cultures and economies of dozens of First Nations who know it as Murrundi and other names, and who regard flowing water as a living ancestor rather than a commodity.^[4]

Over the past two decades, climate change, over-extraction and prolonged drought have exposed how fragile this system can be, from choking algal blooms to the ecological trauma of the Millennium Drought and the fish kills at Menindee.^[3]

Governments have responded with the Murray–Darling Basin Plan, which aims to return more water to the river, but the Plan is now being tested by a hotter, drier and more volatile climate.^[5]

As the Basin Plan approaches key review points and climate projections harden, the River Murray has become a frontline test of whether Australia can share a shrinking resource fairly while keeping a vast river system alive.^[6]

Scale, shape and character of a working river

The River Murray is Australia's longest river, flowing for about 2,508 kilometres from its headwaters in the Australian Alps of New South Wales and Victoria to the Murray Mouth at the Coorong in South Australia.^[1]

It is part of the Murray–Darling Basin, an inland catchment of roughly one million square kilometres that collects water from mostly semi-arid landscapes before delivering it through locks, weirs and barrages to the Southern Ocean.^[1]

The river's natural flow once rose and fell with the seasons, with snowmelt and winter–spring rain driving high flows and periodic floodplain inundation, and hot summers bringing reduced baseflows.^[1]

Over the past century, large dams, storages and more than a dozen weirs have reshaped those rhythms, smoothing peaks and boosting reliability for irrigation, navigation and urban supply at the cost of reduced flood frequency and altered habitat.^[5]

At its lower end, the system fans out into the Lower Lakes and Coorong, a complex of freshwater and estuarine wetlands where the balance between river inflows, tides and evaporation is tightly managed through barrages.^[5]

Salinity is a constant management challenge, as clearing, irrigation and reduced flows mobilise ancient salts in soils and groundwater, threatening crops, infrastructure and the health of river red gum floodplains.^[5]

Economic engine, ecological lifeline, cultural home

The River Murray underpins one of Australia's most productive food bowls, supporting irrigated industries such as cotton, rice, grapes, citrus, almonds, dairy and horticulture worth several billion dollars a year in gross value.^[2]

The river and its storages supply drinking water to inland centres including Adelaide, regional cities such as Mildura and Albury–Wodonga, and countless smaller communities along its length.^[2]

Tourism, recreation and houseboat industries also rely on Murray flows, drawing visitors to fishing grounds, wetlands, national parks and riverside towns in all three downstream states.^[2]

Ecologically, the Murray supports internationally recognised wetlands such as the Barmah–Millewa Forest, Chowilla Floodplain, Hattah Lakes and the Coorong and Lakes Alexandrina and Albert Ramsar sites, which provide habitat for waterbirds, native fish and floodplain forests.^[5]

Many of these ecosystems depend on periodic overbank floods that recharge billabongs, wetlands and groundwater, disperse nutrients and trigger fish breeding and bird nesting events.^[14]

When these floods are too rare or too small because of extractions and climate change, river red gums stress, black box woodlands thin, and native fish and bird populations decline.^[5]

For First Nations across the basin, including the Ngarrindjeri at the Murray Mouth and the First Peoples of the River Murray and Mallee in South Australia, the river is a cultural landscape embedded in creation stories, law, ceremony and day-to-day subsistence.^[4]

Traditional Owners have long argued that "cultural flows" – water entitlements owned and managed by Indigenous nations to sustain cultural, spiritual and economic values – must sit alongside environmental and consumptive uses in basin planning.^[15]

Climate change, extremes and water quality stress

Australia has already warmed by about 1.5 degrees since 1910, and this has intensified heatwaves, increased evaporation and altered rainfall patterns over the Murray–Darling Basin.^[13]

CSIRO and Bureau of Meteorology analyses show significant declines in cool-season rainfall and streamflows in the southern basin, with roughly one third of gauges recording reduced annual flows and fewer days of high flows.^[13]

For the Murray, this means less reliable runoff from key catchments, more frequent low flows and a greater reliance on large storages to buffer years of drought.^[10]

Climate modelling for the Basin suggests that a 5 percent drop in average annual rainfall by mid-century could translate into around a 20 percent reduction in average runoff, amplifying pressure on allocations even in non-drought years.^[10]

Hotter, drier periods increase the risk of blue-green algal blooms, hypoxic "blackwater" events and fish kills, as low flows, warm water and high nutrient loads deplete oxygen and stress aquatic life.^[16]

The 2018–19 Menindee fish kills in the Darling–Baaka and subsequent blackwater episodes downstream highlighted how compounded stresses from drought, over-extraction and extreme heat can push river ecosystems past tipping points.^[13]

Conversely, climate change is also associated with more intense rainfall events, and the 2022–23 River Murray high flow was the second highest on record, delivering major ecological benefits but also widespread flooding and water quality risks.^[16]

These extremes create management dilemmas, because operators must juggle flood mitigation, environmental outcomes and consumptive supply in a system with finite storage and rapidly changing inflows.^[19]

Who gets the water, and how is it changing?

Water in the Murray is governed under the Murray–Darling Basin Plan, agreed in 2012 under the Commonwealth Water Act and implemented through state water resource plans, water sharing rules and a cap on overall diversions.^[17]

The Plan sets a sustainable diversion limit and has recovered more than 2,100 gigalitres of water entitlements across the basin for environmental use, largely through buybacks and irrigation efficiency projects.^[17]

Commonwealth and state environmental water holders now coordinate releases to mimic aspects of natural flow regimes, targeting key wetlands, floodplains and channel habitats along the Murray and its tributaries.^[14]

Evaluation by South Australian agencies suggests that environmental watering has improved connectivity, water quality and habitat condition in many Murray floodplain and wetland assets, even as broader pressures persist.^[11]

At the same time, irrigators, towns and industries continue to depend heavily on reliable allocations, and water markets allow entitlements and temporary allocations to be traded across regions and sectors.^[17]

During droughts, high-security entitlements and critical human needs, including basic town water supplies and certain cultural and environmental requirements, are prioritised, but low-security users can face severe allocation cuts.^[17]

First Nations groups have secured only a small fraction of basin water entitlements despite their recognised rights and interests, and many are calling for dedicated cultural water allocations in future Basin Plan reforms.^[18]

Groundwater is an often overlooked part of the picture, yet studies point to falling levels in several major alluvial systems under both extraction and climate change, with implications for baseflows and long-term reliability.^[19]

Future water security and what must happen next

Climate projections for south-eastern Australia point towards a future of higher temperatures, more frequent hot and dry years, shorter and sharper floods, and increasing evaporation losses from storages and floodplains.^[13]

For the River Murray, this means the historical record is no longer a safe guide, and planners must stress-test water sharing rules, infrastructure and environmental watering programs against more extreme scenarios.^[10]

Analyses underpinning the Basin Plan review process emphasise that current diversion limits and recovery targets may not be enough to protect key ecological assets and water quality under mid- to high-emissions climate pathways.^[19]

Regional planners will need to consider more ambitious water recovery, smarter use of constraints relaxation to deliver overbank flows, and closer integration of surface water and groundwater management.^[11]

They will also have to grapple with difficult questions about land use, such as whether some high-water-demand crops and marginal irrigation areas will remain viable under tighter limits and more volatile allocations.^[17]

For policymakers, the challenge is to align climate mitigation, adaptation and water policy, ensuring that basin communities, First Nations and ecosystems are not left to absorb the costs of deferred decisions.^[18]

That will require firm national emissions cuts to reduce long-term warming, robust funding for adaptation and river restoration, and genuine power-sharing with Traditional Owners over how water is owned, governed and used.^[13]

If governments treat the River Murray as a barometer of climate readiness, rather than a reservoir to be exhausted, the choices made this decade can still bend the system towards a more resilient and just future.^[6]

What regional planners and policymakers must focus on

Regional planners now face a narrowing climate window and must prioritise rigorous climate modelling, transparent trade-offs and scenario planning that acknowledges declining average flows and more volatile extremes.^[10]

They need to update land-use and settlement strategies so that new housing, irrigation expansion and industrial growth occur in locations with secure, climate-robust water sources rather than in already stressed reaches.^[19]

Policymakers must ensure the next Basin Plan review strengthens, rather than weakens, sustainable diversion limits, and that environmental water portfolios are large and flexible enough to maintain key ecological functions under harsher conditions.^[11]

Embedding Indigenous water rights, co-governance and cultural flows in legislation and planning will be essential for both justice and resilience, because Traditional Owner knowledge offers locally grounded insight into how rivers respond to change.^[18]

Targeted investment in demand management, efficient urban and agricultural use, and nature-based solutions such as wetland restoration can buy critical time as climate impacts intensify.^[14]

Above all, the River Murray forces a clear choice on governments: whether to plan early for a future with less water, or to wait for the next crisis and again discover the costs of treating climate risk as tomorrow's problem.^[6]

References

1. Murray–Darling Basin Authority – Rivers of the Basin
2. Murray–Darling Basin Authority – Basin economy and communities
3. CSIRO & Bureau of Meteorology – Australia's changing climate
4. South Australian Government – Traditional Owners of the SA River Murray
5. South Australian Government – Basin Plan and environmental outcomes for the River Murray, Lower Lakes and Coorong
6. Productivity Commission – Murray–Darling Basin Plan Review submissions
7. South Australia State of the Environment – River Murray environmental challenges
8. South Australian Government – Basin Plan monitoring and evaluation
9. CSIRO & Bureau of Meteorology – State of the Climate
10. Commonwealth Environmental Water Holder – Flow-MER program
11. AIATSIS – Cultural flows in Murray River Country
12. Goyder Institute – 2022–23 River Murray high flow environmental response
13. National Irrigators' Council – Murray–Darling Basin Plan overview
14. Australian Human Rights Commission – Water and Indigenous rights in the Murray–Darling Basin
15. CSIRO – Submission to the Murray–Darling Basin Plan Review 2023

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We discovered microbes in bark ‘eat’ climate gases. This will change the way we think about trees - The Conversation

The Conversation - Luke Jeffrey  Chris Greening  Damien Maher  Pok Man Leung

boris misevic knqZ N qJQk unsplash. Boris Misevic/Unsplash, CC BY

Authors Luke Jeffrey, Postdoctoral Research Fellow, Southern Cross University Chris Greening, Professor, Microbiology, Monash University Damien Maher, Professor in Earth Sciences, Southern Cross University Pok Man Leung, Research Fellow in Microbiology, Monash University Key Points Bark contains up to 6 trillion microbial cells per square meter, comparable to stars in 60 Milky Way galaxies, forming active communities across species like paperbarks and eucalypts.​ Microbes perform "aerotrophy," metabolising atmospheric gases including methane (a key warming driver), toxic carbon monoxide, and hydrogen for energy.​ Wetland trees host methanotrophs that eat methane internally, while all tested trees consistently remove hydrogen at every height and forest type.​ Globally, tree bark's surface area rivals Earth's land, enabling microbes to remove ~55 million tonnes of hydrogen yearly, indirectly offsetting up to 15% of human methane emissions.​ Bark also clears carbon monoxide, aiding urban air quality where levels are high from fossil fuels.​ Findings suggest prioritising gas-eating microbe species in reforestation could enhance climate strategies, conservation, and carbon accounting.

We all know trees are climate heroes. They pull carbon dioxide out of the air, release the oxygen we breathe, and help combat climate change.

Now, for the first time, our research has uncovered the hidden world of the tiny organisms living in the bark of trees. We discovered they are quietly helping to purify the air we breathe and remove greenhouse gases.

These microbes “eat”, or use, gases like methane and carbon monoxide for energy and survival. Most significantly, they also remove hydrogen, which has a role in super-charging climate change.

What we discovered has changed how we think about trees. Bark was long assumed to be largely biologically inert in relation to climate. But our findings show it hosts active microbial communities that influence key atmospheric gases. This means trees affect the climate in more ways than we previously realised.

The Australian paperbark tree is a hardy wetland species and 
a hotspot for microbial life. Luke Jeffrey, CC BY-ND

Teeming with life

Over the past five years, collaborative research between Southern Cross and Monash universities studied the bark of eight common Australian tree species. These included forest trees such as wetland paperbarks and upland eucalypts. We found the trees in these contrasting ecosystems all shared one thing in common: their bark was teeming with microscopic life.

We estimate a single square metre of bark can hold up to 6 trillion microbial cells. That’s roughly the same number of stars in about 60 Milky Way galaxies, all squeezed onto the surface area of a small table.

To find out what these bark microbes were doing, we first used a technique called metagenomic sequencing. In simple terms, this method reads the DNA of every microorganism in a sample at once. If normal DNA sequencing is like reading one book, metagenomics is like scanning an entire library. We pulled out clues about who lived in the bark and which “tools” or enzymes they might have.

Dr Bob Leung preparing bark samples for lab measurements at Monash University. Jialing Zeng, CC BY-ND

A simple analogy is to imagine a construction site where each tradespeople carries different tools. While some tools overlap, many are specific to their trade. If you see a pipewrench, you can deduce a plumber is around.

In a similar way, metagenomics showed us the “tools” the microbes were carrying in their DNA – genes that let them eat atmospheric gases like methane, hydrogen or carbon monoxide. This gave us valuable insight into what the bark microbes could do.

But, like a construction site, having tools doesn’t mean the “tradies” are using them for jobs all the time. So we also measured the movement of gases in and out of the bark to see which microbial “jobs” were happening in real time. 

The research team taking field measurements and collecting bark samples in tropical forests near Darwin. Luke Jeffrey, CC BY-ND

Bark microbes eat gases

Many of the microbes living in bark can live off various gases. This is a process recently coined as “aerotrophy”, as in “air eaters”. Some of their favourite gases include methane, hydrogen and carbon monoxide, all of which affect the climate and the quality of the air we breath.

Methane is a potent greenhouse gas, responsible for about one third of human-induced warming. We found most wetland trees contained specialist bacteria called methanotrophs, that eat methane from within the tree.

We also saw abundant microbial enzymes that remove carbon monoxide, a toxic gas for both humans and animals. This suggests tree bark helps clean the air we breathe. This could be particularly useful in urban forests, as cities often have elevated levels of this harmful and odourless gas.

But one finding stood out above all others. Within every tree species examined, in every forest type, and at every stem height, bark microbes consistently removed hydrogen from the air. In other words, trees could be a major, previously unrecognised, global natural system for drawing down hydrogen out of the atmosphere.

Measuring paperbark tree stem gases using a stem gas flux chamber in a freshwater wetland. Luke Jeffrey, CC BY-ND

Global possibilities

When we scaled up what these microbes were doing across all trees globally, the potential impact becomes striking. There are about 3 trillion trees on Earth, and together their bark has a huge cumulative surface area, rivalling that of the entire land surface of the planet.

Taking this into account, our calculation suggests that tree-microbes could remove as much as 55 million tonnes of hydrogen from the atmosphere each year.

Why does this matter? Hydrogen affects our atmosphere in ways that influence the lifetime of other greenhouse gases – especially methane. In fact, hydrogen emissions may be “supercharging” the warming impact of methane.

By using a simple model, the annual amount of hydrogen removed by bark microbes may indirectly offset up to 15% of annual methane emissions caused by humans.

In other words, if tree bark microbes weren’t doing this work, there would be more methane in the atmosphere, and our rising methane problem could be even bigger.

This also hints at another exciting possibility: planting trees could expand this microbial atmosphere-cleaning potential, giving microbes more surface area to apply their trade and help remove even more climate damaging gases from the air.

The ‘barkosphere’

Our research points to many exciting new possibilities and uncertainties around the previously hidden role of a tree’s “barkosphere”.

We want to know which tree species host the most active “gas-eating” microbes, which forests remove the most methane, carbon monoxide or hydrogen, and how climate change may alter these communities and their activities.

This knowledge could help guide future reforestation, conservation, carbon accounting strategies. It may even change the way we try and limit climate change.

Trees have always regulated our climate. But now we know their bark – and the hard working microscopic ecosystems living inside – may be far more important than previously thought. 

The results of this research could have major implications for how we use trees to combat global warming. 
Luke Jeffrey, CC BY-ND

References

• The climate case for planting trees has been overhyped – but it’s not too late to fix it.
• Tree- bark microbiomes drive global hydrogen sinks and atmospheric trace gas cycling.
• How many stars are in the universe?.
• Metagenomics: Genomes of the unseen majority.Microbial aerotrophy enables continuous primary production in diverse cave ecosystems.
• Global Methane Pledge: Cutting methane emissions to fight climate change.
• We found methane-eating bacteria living in a common Australian tree. It could be a game changer for curbing greenhouse gases.
• Mapping tree density at a global scale.
• Global surface area and climate role of tree bark
• Hydrogen emissions are “supercharging” the warming impact of methane.
• Methane emissions are turbocharging climate change. These quick fixes could slow it down.
• We discovered microbes in bark ‘eat’ climate gases. This will change the way we think about trees.