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Living planktonic foraminifera photos by Haruka Takagi, Katsunori Kimoto, Tetsuichi Fujiki, Hiroaki Saito, Christiane Schmidt4 , Michal Kucera and Kazuyoshi Moriya5, CC BY-SA 4.0 via Wikimedia Commons

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1) Orbulina universa, (2) Sphaeroidinella dehiscens, (3) Globigerinoides sacculifer, (4) Globigerinoides conglobatus, (5) Globigerinoides ruber (white), (6) Globigerinoides ruber (pink), (7) Globoturborotalita rubescens, (8) Globoturborotalita tenella, (9) Globigerinella calida, (10) Globigerinella siphonifera Type I, (11) Globigerinella siphonifera Type II, (12) Globigerinella adamsi, (13) Globigerina bulloides, (14) Turborotalita quinqueloba, (15) Turborotalita humilis, (16) Hastigerina pelagica, (17) Hastigerinella digitata, (18) Neogloboquadrina incompta, (19) Neogloboquadrina pachyderma, (20) Neogloboquadrina dutertrei, (21) Pulleniatina obliquiloculata, (22) Globorotalia inflata, (23) Globorotalia menardii, (24) Globorotalia scitula, (25) Globorotalia crassaformis, (26) Globorotalia truncatulinoides, (27) Candeina nitida, (28) Globigerinita glutinata, (29) Globigerinita uvula, and (30) Tenuitella fleisheri. Images by Haruka Takagi, Katsunori Kimoto, Tetsuichi Fujiki, Hiroaki Saito, Christiane Schmidt , Michal Kucera and Kazuyoshi Moriya CC BY-SA 4.0 via Wikimedia Commons

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This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Global temperature records are expected to exceed the 1.5 °C threshold for the first time this year. This has happened much sooner than predicted. So can life on the planet adapt quickly enough?

In our new research, published today in Nature, we explored the ability of tiny marine organisms called plankton to adapt to global warming. Our conclusion: some plankton are less able to adapt now than they were in the past.

Plankton live in the top few metres of ocean. These algae (phytoplankton) and animals (zooplankton) are transported by ocean currents as they do not actively swim.

Climate change is increasing the frequency of heatwaves in the sea. But predicting the future effects of climate change is difficult because some projections depend on ocean physics and chemistry, while others consider the effects on ecosystems and their services.

Some data suggest that current climate change have already altered the marine plankton dramatically. Models project a shift of plankton towards both poles (where ocean temperatures are cooler), and losses to zooplankton in the tropics but might not predict the patterns we see in data. Satellite data for plankton biomass are still too short term to determine trends through time.

To overcome these problems, we have compared how plankton responded to past environmental change and modelled how they could respond to future climate changes. As the scientist Charles Lyell said, “the past is the key to the present”.

We explored one of the best fossil records from a group of marine plankton with hard shells called Foraminifera. This comprehensive database of current and past distributions, compiled by researchers at the University of Bremen, has been collected by hundreds of scientists from the seafloor across the globe since the 1960s. We compared data from the last ice age, around 21,000 years ago, and modern records to see what happened when the world has previously warmed.

We used computational models, which combine climate trends with traits of marine plankton and their effect on marine plankton, to simulate the oceanic ecosystems from the last ice age to the pre-industrial age. Comparing the model with the data from the fossil record is giving us support that the model simulated the rules determining plankton growth and distribution.

We found that some subtropical and tropical species’ optimum temperature for peak growth and reproduction could deal with seawater warming in the past, supported by both fossil data and model. Colder water species of plankton managed to drift to flourish under more favourable water temperatures.

Our analysis shows that Foraminifera could handle the natural climate change, even without the need to adapt via evolution. But could they deal with the current warming and future changes in ocean conditions, such as temperature?

Future of the food chain

We used this model to predict the future under four different degrees of warming from 1.5 to 4 °C. Unfortunately, this type of plankton’s ability to deal with climate change is much more limited than it was during past warming. Our study highlights the difference between faster human-induced and slower-paced geological warming for marine plankton. Current climate change is too rapid and is reducing food supply due to ocean stratification, both making plankton difficult to adapt to this time.

Phytoplankton produce around 50% of the world’s oxygen. So every second breath we take comes from marine algae, while the rest comes from plants on land. Some plankton eat other plankton. That in turn gets eaten by fish and then marine mammals, so energy transfers further up the food chain. As it photosynthesises, phytoplankton is also a natural carbon fixation machine, storing 45 times more carbon than the atmosphere.

Around the world, many people depend heavily on food from the ocean as their primary protein sources. When climate change threatens marine plankton, this has huge knock-on effects throughout the rest of the marine food web. Plankton-eating marine mammals like whales won’t have enough food to prey on and there’ll be fewer fish to eat for predators (and people). Reducing warming magnitude and slowing down the warming rate are necessary to protect ocean health.

Glacier terminal undercut by warm water image by Sonny Whitelaw

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Shaun Eaves, Te Herenga Waka — Victoria University of Wellington; Andrew Mackintosh, Monash University; Helen Bostock, The University of Queensland, and Joel Pedro

Recent assessments suggest the ocean current known as Atlantic Meridional Overturning Circulation (AMOC) is slowing down, with collapse a real possibility this century.

The AMOC is a globally important current in the Atlantic Ocean, where surface water moves northward as part of the Gulf Stream and transports warm water towards the Arctic. There it cools and sinks to return southward as a deep ocean current.

Map of sea surface temperatures in the North Atlantic with a schematic diagram of ocean currents.
The Atlantic meridional overturning current (AMOC) transfers heat to the North Atlantic. Recent trends indicate this current may be slowing. Ruijian Gou, CC BY-ND

Collapse of the AMOC would have a devastating effect on climate in Europe. Temperatures in the UK and Scandinavia could drop by 5–15°C in a matter of decades.

However, because Earth’s climate system is interconnected, these impacts could have a global reach. Our new research shows past changes in AMOC have had significant impact on temperatures in New Zealand and across the southern hemisphere. These results imply that future collapse of AMOC may accelerate ongoing warming trends.

Lessons from the past

Between 20,000 and 10,000 years ago, Earth transitioned from peak ice-age conditions to a climate more like today’s. This interval featured rising global temperatures, melting ice sheets and climbing sea levels – all phenomena associated with present-day climate change.

Evidence from ice cores in Greenland and marine sediments in the North Atlantic suggests this natural warming event featured several abrupt changes associated with AMOC variability.

Using this interval as a natural experiment, we have undertaken research to learn more about how AMOC variability can affect climate in New Zealand.

Two merged photographs show a glacial basin and people among snow-covered rocks.
Evidence preserved in the landscape shows cooling and glacier growth in New Zealand coincided with a strengthening AMOC 14,500 years ago. Huw Horgan, Shaun Eaves, CC BY-ND.

To reconstruct how air temperature changed in New Zealand, we examined the past extent of mountain glaciers using evidence preserved in the landscape. Glaciers grow and shrink primarily in response to changing air temperature, which affects the annual balance of snowfall and snow or ice melt. As glaciers change in size, they deposit moraines (rock debris) in the landscape, which can persist for tens of thousands of years.

A female scientist wearing a hard hat inspects mud layers in a sediment core.
The analysis of microfossils in marine sediment cores allows scientists to reconstruct past changes in sea-surface temperature. Jenni Hopkins, CC BY-ND

We combined these land-based observations with reconstructions of sea-surface temperature in the Tasman Sea, which we derived from microfossils (smaller than one millimetre in size) known as foraminifera. These microfossils come in a wide range of species and each has a preferred water temperature.

We quantified changes in foraminifera species in a core of marine sediment to trace how local temperature in the Tasman Sea has varied through time.


Global climate connections

Our results show that changes in air and sea-surface temperature followed a similar pattern in the New Zealand region as Earth warmed following the last ice age.

Warming began in both air and sea at about 18,000 years ago, followed by a cooling event at about 14,500 years ago – the Antarctic Cold Reversal. The timing of these changes matches past changes in the AMOC, as recorded in geological climate records from the North Atlantic region.

We examined computer simulations to test the physical connection between changes in the AMOC and New Zealand’s climate. These simulations used a physics-based climate model that captures atmospheric and ocean circulation and their interaction.

Outputs from climate models show southern hemisphere temperature changes due to AMOC variability.
Climate model experiments show the impact of past AMOC variability on surface temperature in the Southern Hemisphere. Shaun Eaves, CC BY-ND

The model simulations support our geological evidence, showing air and sea surface temperatures in New Zealand respond sensitively to changes in AMOC intensity. When the AMOC weakens and Europe cools, New Zealand and the southern mid-latitudes undergo warming, and vice versa.

The models also indicate changes in the AMOC are transported rapidly, within decades, to New Zealand via shifting global wind systems. Changes in the AMOC disrupt the temperature gradient between the hemispheres, which is a key control on the strength of westerly wind belts in the southern hemisphere, between the latitudes of 40°S and 60°S where New Zealand is.

The westerly winds are important for New Zealand’s climate. They control the path of atmospheric storms and regional ocean currents.

Stronger winds over New Zealand bring regional cooling, as more storms track over the country and warm ocean currents are diverted away from the Tasman Sea into the south Pacific. In contrast, when the AMOC weakens, New Zealand has clearer skies and the Tasman Sea receives more tropical water masses, causing regional warming.

Future implications

Scientists have identified several “tipping points” in Earth’s climate system that may be triggered by human-caused climate change. Once these thresholds are crossed, the consequences cannot be easily undone.

Climbing greenhouse gas concentrations have raised air temperatures in New Zealand, and globally, by about 1.1°C since the late 19th century. Projections suggest New Zealand may end this century 1°C to 3°C warmer than now. However, these estimates do not include the potential impacts of a future AMOC collapse.

Our insights from the recent geological past show this AMOC tipping point has global reach, and could accelerate future warming in New Zealand.The Conversation

Shaun Eaves, Senior Lecturer in Physical Geography, Te Herenga Waka — Victoria University of Wellington; Andrew Mackintosh, Chief Investigator in Antarctic environmental science, Monash University; Helen Bostock, Associate Professor in Marine Geology, The University of Queensland, and Joel Pedro, Palaeoclimatologist

This article is republished from The Conversation under a Creative Commons license. Read the original article.

blue carbon

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Authors: Kerrylee Rogers, Associate Professor, University of Wollongong; Jeffrey Kelleway, Postdoctoral Research Fellow in Environmental Sciences, Macquarie University, and Neil Saintilan, Head, Department of Environmental Science, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Coastal wetlands don’t cover much global area but they punch well above their carbon weight by sequestering the most atmospheric carbon dioxide of all natural ecosystems.

Termed “blue carbon ecosystems” by virtue of their connection to the sea, the salty, oxygen-depleted soils in which wetlands grow are ideal for burying and storing organic carbon.

In our research, published in Nature, we found that carbon storage by coastal wetlands is linked to sea-level rise. Our findings suggest as sea levels rise, these wetlands can help mitigate climate change.

Sea-level rise benefits coastal wetlands

We looked at how changing sea levels over the past few millennia has affected coastal wetlands (mostly mangroves and saltmarshes). We found they adapt to rising sea levels by increasing the height of their soil layers, capturing mineral sediment and accumulating dense root material. Much of this is carbon-rich material, which means rising sea levels prompt the wetlands to store even more carbon.

We investigated how saltmarshes have responded to variations in “relative sea level” over the past few millennia. (Relative sea level is the position of the water’s edge in relation to the land rather than the total volume of water within the ocean, which is called the eustatic sea level.)

What does past sea-level rise tell us?

Global variation in the rate of sea-level rise over the past 6,000 years is largely related to the proximity of coastlines to ice sheets that extended over high northern latitudes during the last glacial period, some 26,000 years ago.

As ice sheets melted, northern continents slowly adjusted elevation in relation to the ocean due to flexure of the Earth’s mantle.

Karaaf Wetlands in Victoria, Australia. Boobook48/flickr, CC BY-NC-SA

For much of North America and Europe, this has resulted in a gradual rise in relative sea level over the past few thousand years. By contrast, the southern continents of Australia, South America and Africa were less affected by glacial ice sheets, and sea-level history on these coastlines more closely reflects ocean surface “eustatic” trends, which stabilised over this period.

Our analysis of carbon stored in more than 300 saltmarshes across six continents showed that coastlines subject to consistent relative sea-level rise over the past 6,000 years had, on average, two to four times more carbon in the upper 20cm of sediment, and five to nine times more carbon in the lower 50-100cm of sediment, compared with saltmarshes on coastlines where sea level was more stable over the same period.

In other words, on coastlines where sea level is rising, organic carbon is more efficiently buried as the wetland grows and carbon is stored safely below the surface.

Give wetlands more space

We propose that the difference in saltmarsh carbon storage in wetlands of the southern hemisphere and the North Atlantic is related to “accommodation space”: the space available for a wetland to store mineral and organic sediments.

Coastal wetlands live within the upper portion of the intertidal zone, roughly between mean sea level and the upper limit of high tide.

These tidal boundaries define where coastal wetlands can store mineral and organic material. As mineral and organic material accumulates within this zone it creates layers, raising the ground of the wetlands.

The coastal wetlands of Broome, Western Australia. Shutterstock

New accommodation space for storage of carbon is therefore created when the sea is rising, as has happened on many shorelines of the North Atlantic Ocean over the past 6,000 years.

To confirm this theory we analysed changes in carbon storage within a unique wetland that has experienced rapid relative sea-level rise over the past 30 years.

When underground mine supports were removed from a coal mine under Lake Macquarie in southeastern Australia in the 1980s, the shoreline subsided a metre in a matter of months, causing a relative rise in sea level.

Following this the rate of mineral accumulation doubled, and the rate of organic accumulation increased fourfold, with much of the organic material being carbon. The result suggests that sea-level rise over the coming decades might transform our relatively low-carbon southern hemisphere marshes into carbon sequestration hot-spots.

How to help coastal wetlands

The coastlines of Africa, Australia, China and South America, where stable sea levels over the past few millennia have constrained accommodation space, contain about half of the world’s saltmarshes.

Saltmarsh on the shores of Westernport Bay in Victoria. Author provided

A doubling of carbon sequestration in these wetlands, we’ve estimated, could remove an extra 5 million tonnes of CO₂ from the atmosphere per year. However, this potential benefit is compromised by the ongoing clearance and reclamation of these wetlands.

Preserving coastal wetlands is critical. Some coastal areas around the world have been cut off from tides to lessen floods, but restoring this connection will promote coastal wetlands – which also reduce the effects of floods – and carbon capture, as well as increase biodiversity and fisheries production.

In some cases, planning for future wetland expansion will mean restricting coastal developments, however these decisions will provide returns in terms of avoided nuisance flooding as the sea rises.

Finally, the increased carbon storage will help mitigate climate change. Wetlands store flood water, buffer the coast from storms, cycle nutrients through the ecosystem and provided vital sea and land habitat. They are precious, and worth protecting.

The authors would like to acknowledge the contribution of their colleagues, Janine Adams, Lisa Schile-Beers and Colin Woodroffe.

Mycorrhizal fungi growing with a plant root by Yoshihiro Kobae

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Image: Mycorrhizal fungi growing with a plant root Dr Yoshihiro Kobae.


This article is republished from The Conversation under a Creative Commons license. Read the original article.

Authors: Adam Frew, Lecturer and ARC DECRA Fellow, Western Sydney University; Carlos Aguilar-Trigueros, Postdoctoral fellow, Western Sydney University; Jeff Powell, Professor and ARC Future Fellow, Western Sydney University, and Natascha Weinberger, Postdoctoral Research Fellow, Western Sydney University

Beneath our feet, remarkable networks of fungal filaments stretch out in all directions. These mycorrhizal fungi live in partnership with plants, offering nutrients, water and protection from pests in exchange for carbon-rich sugars.

Now, new research shows this single group of fungi may quietly be playing a bigger role in storing carbon than we thought.

How much bigger? These microscopic filaments take up the equivalent of more than a third (36%) of the world’s annual carbon emissions from fossil fuels – every year.

As we search for ways to slow or stop the climate crisis, we often look to familiar solutions: cutting fossil fuel use, switching to renewables and restoring forests. This research shows we need to look down too, into our soils.

This shows how mycorrhizal fungi (fine white filaments) connect to plant root systems (yellow) and out into the soil. Scivit/Wikipedia


This fungi-plant partnership is 400 million years old

Mycorrhizal fungi are hard to spot, but their effects are startling. They thread networks of microscopic filaments through the soil and into the roots of almost every plant on earth.

But this is no hostile takeover. They’ve been partnering with plants for more than 400 million years. The length of these complex relationships has given them a vital role in our ecosystems.

Sometimes fungi take more than they give. But often, these are relationships of mutual benefit. Through their network, the fungi transport essential nutrients and water to plants, and can even boost their resistance to pests and disease.

In return, plants pump sugars and fat made by photosynthesis in their leaves down through their roots to the fungi. These compounds are rich in carbon, taken from the atmosphere.

How do these fungi fit into the carbon cycle?

On land, the natural carbon cycle involves a delicate balance. Plants take CO₂ from the atmosphere through photosynthesis, while other organisms emit it back into the atmosphere.



Carbon is captured by plants through photosynthesis, some of this carbon then goes into the networks of mycorrhizal fungi. These fungi also will release some of this carbon as CO₂ and as compounds into the soil. Adam Frew/Author provided using BioRender

Now we know the carbon transfer from plants to mycorrhizal fungi isn’t a side note – it’s a substantial part of this equation.

By analysing almost 200 datasets, the researchers estimate the world’s plants are transferring a staggering 3.58 billion tonnes of carbon per year to this underground network. That’s the same as 13.12 billion tonnes of CO₂ – more than a third of the world’s 36.3 billion tonnes of CO₂ emitted yearly by burning fossil fuels.

To be clear, fungal carbon doesn’t present a climate solution by itself. It’s a missing piece in the carbon cycle puzzle.

We still have big gaps in data from particular ecosystems and geographic regions. For instance, this study didn’t have any data of this kind from Australia or Southeast Asia – because it doesn’t yet exist.

Microscope image of plant roots that have been stained to show the mycorrhizal fungal inside the root of a plant.
This image shows mycorrhizal fungi (blue) growing inside plant roots, where they obtain carbon and provide plants with access to resources such as nutrients. Adam Frew


What does this mean for the climate?

We already know mycorrhizal fungi help soils retain carbon by releasing specific chemical compounds. These compounds contain carbon and nitrogen. Once in the soil, these compounds can be used by other soil microorganisms, such as bacteria. When this happens it helps to form a highly stable soil carbon store that is more resistant to breakdown, and this store can accumulate more than four times faster in the presence of mycorrhizal fungi.

When these fungi die, they leave behind “necromass” – a complex scaffold of dead organic material which can be stored in soil, and often inside clumps of soil particles. The carbon inside these clumps can stay in the soil for close to a decade without being released back to the atmosphere.

In fact, other studies suggest this fungal necromass might contribute more to the carbon content of soil than living fungi.

But these fungi also naturally cause carbon to escape back to the atmosphere by decomposing organic matter or changing water and nutrient availability, which influences how other organisms decompose. Mycorrhizal fungi also release some carbon back into the atmosphere, though the rate this happens depends on many factors.

What does this mean for climate change? While atmospheric CO₂ concentrations keep rising, it doesn’t necessarily mean fungi are storing more of it. Recent research in an Australian woodland found higher atmospheric CO₂ did see more carbon sent below the ground. But this carbon wasn’t stored for long periods.

To date, mycorrhizal fungi have been poorly represented in global carbon cycle models. They aren’t often considered when assessing which species are at risk of extinction or promoting successful restorations.

We need more research to better understand the role of mycorrhizal fungi in the carbon cycle across different ecosystems, including in agriculture. Dylan de Jonge/Unsplash


Protecting our fungal networks

When we cut down forests or clear land, we not only disrupt life above the ground, but underground as well. We need to safeguard these hidden fungal networks which give our plants resilience – and play a key role in the carbon cycle.

As we better understand how these fungi work and what we’re doing to them, we can also develop farming methods which better preserve them and their carbon.

As global and Australian initiatives continue to map the diversity of mycorrhizal fungi, scientists are working to understand what shapes these communities and their roles.

We’ve long overlooked these vital lifeforms. But as we learn more about how fungi and plants cooperate and store carbon, it’s well past time for that to change. The Conversation