Category: Ecosystems

Climate change is forcing butterflies and moths to adapt – but some species can’t

Climate change is forcing butterflies and moths to adapt – but some species can’t

By Callum Macgregor

Butterflies are rather like Goldilocks, preferring conditions to be neither too hot nor too cold, but “just right”. Under climate change, the temperature at any given time of summer is, on average, getting warmer, leaving butterflies (and their nocturnal cousins, the moths) with the challenge of how to remain in their optimal temperature window.

One of the main ways in which species are achieving this is by changing the time of year at which they are active. Scientists refer to the timing of such lifecycle events as “phenology”, so when an animal or plant starts to do things earlier in the year it is said to be “advancing its phenology”.

These advances have been observed already in a wide range of butterflies and moths – indeed, most species are advancing their phenology to some extent. In Britain, as the average spring temperature has increased by roughly 0.5°C over the past 20 years, species have advanced by between three days and a week on average, to keep track of cooler temperatures.

Is this a sign that butterflies and moths are well equipped to cope with climate change, and readily adjust to new temperatures? Or are these populations under stress, being dragged along unwillingly by unnaturally fast changes?

In a new study published in Nature Communications, colleagues and I sought to answer this question. We first pulled together data from millions of records submitted by butterfly and moth enthusiasts to one of four recording schemes run by charities or research institutes. This gave us information on 130 species of butterflies and moths in Great Britain every year for a 20-year period between 1995 and 2014. We could then estimate the abundance and distribution of each species across this time, along with how far north they had moved. The data also, crucially, allowed us to estimate subtle changes in what time of the year each species was emerging from the chrysalis as a fully-grown butterfly.

It pays to reproduce quickly

Analysing the trends in each variable, we discovered that species with more flexible lifecycles were more likely to be able to benefit from an earlier emergence driven by climate change. Some species are able to go from caterpillar to butterfly twice or more per year, so that the individual butterflies you see flying in the spring are the grandchildren or great-grandchildren of the individuals seen a year previously.

Among these species, we observed that those which have been advancing their phenology the most over the 20-year study period also had the most positive trends in abundance, distribution and northwards extent. For these species – such as Britain’s tiniest butterfly, the dainty small blue – emerging early in spring gives more time for their later-summer generations to complete their reproductive cycles before the arrival of autumn, allowing more population growth to occur.

Small blue: Britain’s tiniest butterfly. Callum Macgregor, Author provided

Other species, however, are less flexible and restricted to a single reproductive cycle per year. For these species, we found no evidence of any benefit to emerging earlier. Indeed, worryingly, we found that the species in this group that specialise in one very specific habitat type (often related to the caterpillar’s preferred diet) actually tended to most harmed by advancing phenology.

The beautiful high brown fritillary, often described as Britain’s most endangered butterfly, fits this category perfectly. It is found only alongside the dog-violets that its caterpillar eats, in coppiced woodland and limestone pavement habitats. It’s also a single-generation butterfly that has advanced its phenology. This suggests that climate change, while undoubtedly not the sole cause, might have played a part in the downfall of this species.

The high brown fritillary was once widespread, but is now found in just a few sites in Lancashire and the south-west. Callum Macgregor, Author provided

All is not lost, however. Many of Britain’s single-generation species show the capacity, in continental Europe, to add a second generation in years that are sufficiently warm. Therefore, as the climate continues to warm, species like the silver-studded blue might be able to switch to multiple generations in the UK as well, and thereby begin to extract benefits from the additional warmth, potentially leading to population increases.

Specialists are at risk

More immediately, we can arm ourselves with this knowledge to spot the warning signs of species that may be most at risk. Clearly the single-generation habitat specialists are of particular concern, as many are already endangered or vulnerable – not just the high brown fritillary and silver-studded blue, but also species such as pearl-bordered fritillary, grizzled skipper and the particularly sought-after white admiral of southern England. Multi-generation species that are failing to advance their phenology might also be threatened: into this category falls another of Britain’s most sharply-declining butterflies: the wall brown.

Using this knowledge to help protect moths and butterflies from climate change is not simply important for the sake of the butterflies and moths themselves – these species also play a number of important roles in our ecosystems. Their caterpillars consume vast quantities of plant material, and in turn act as prey for birds, bats, and other small mammals, while moths even act as pollinators of a surprisingly wide range of plant species, possibly including some important crops.

According to Butterfly Conservation, around two-thirds of butterfly species have declined in the UK over the past 40 years. If this trend continues, it might have unpredictable knock-on effects for other species in the ecosystem. Only by arming ourselves with an understanding of why butterfly numbers are down can we hope to halt or reverse the decline.


This article was originally posted on The Conversation
Photo by Ana Martinuzzi on Unsplash
Not just dirt: Why soil health is vital to build climate resilience

Not just dirt: Why soil health is vital to build climate resilience

By Lydia Messling

The IPCC’s recent report on climate change and land, highlighted the pressing need for changes to be made to land management practice. Land degradation and climate change threaten to reduce food production and lead to a 25% food production deficit by mid-century. Globally, soil biodiversity has been estimated to annually contribute between US$ 1.5 and 13 trillion to the value of ecosystems services. Despite this, soil biodiversity is often overlooked in policy. This neglect poses a serious threat to food security.

Producing sufficient food to feed a growing population, relies upon being able to grow healthy crops that survive until harvest season after season. To a large extent, this depends on the health of the thin 30-40cm layer of topsoil that plants grow in. Measuring the soil organic carbon (SOC) of this soil provides an indicator of the soil’s health. When soils reach low levels SOC they can tip past the point where they have any hope of being restored, resulting in devastating irreversible degradation of the land. Poor land management practice, soil erosion, and other land degradation processes can reduce soil health. Climate change and its impacts act as an additional stress factor.

Just as poorly managed soils can exacerbate climate change and reduce food security, healthy soils can have the opposite effect. Sequestering carbon in the soil can help reduce greenhouse gas emissions, as well as improving the soil’s resilience to extreme weather events and also increase crop yields.

How does climate change affect soil health and what can be done?

Through changes in average temperatures, more frequent and intense extreme events, and other factors, climate change can affect soil structure, stability, topsoil water holding capacity, nutrient availability and erosion. The IPCC’s report on land lists many interconnected processes that affect degradation processes, but climate change also directly effects salinization, and permafrost thawing, waterlogging of dry ecosystems and drying of ecosystems, and a broad group of biologically mediated processes like woody encroachment, biological invasions, pest outbreaks, together with biological soil crust destruction and increased burning.

For example, prolonged dry seasons can dry out the soil, causing the organisms in the soil to die and for nutrients to be lost. Similarly, prolonged wet seasons can inundate the soil and wash away the nutrients needed for plant growth, as well as eroding and removing the soil. One of the ways that soil can be made more resilient to climate change is by increasing the soil’s organic matter.

What are soil organic carbon (SOC) and soil organic matter (SOM)?

Soil organic matter (SOM) is divided into ‘living’ and ‘dead’ components, such as roots and microorganisms and decaying plants and animals. SOM contains all sorts of elements such as carbon, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium, and also determines how much water the soil can contain – all important elements for plant growth. SOM is quite hard to measure though, so measurements are taken of Soil Organic Carbon (SOC) instead. About 58% of the mass of organic matter exists as carbon (depending on geography), so the percentage of SOM can be calculated from the SOC measurement. Therefore, a decrease in SOC means a decrease in SOM.

Why is SOM important?

Besides providing crucial plant nutrition, SOM provides soil with its structure. This structure is the reason healthy soil doesn’t just get blown away in the wind, and how plants can spread their roots to remain stable. Soil structure is also important for being able to hold moisture whilst not waterlogging plants and retain nutrients, preventing them from being washed away completely in heavy rains. Land that has been overworked and lost much of its SOM content will have poor soil structure. Farmers may use chemicals to replace the nutrients that have been lost from a lack of SOM but will find it difficult to provide the soil structure that is needed for plants to grow and be resilient to climate impacts.

How can SOM be lost, and how can it be replaced?

Agriculturalists have already been adopting different methods to increase SOM content and to improve soil health, as loss of SOM is also related to intensive farming practices. As such, many methods exist for increasing SOM in soils, many of which are easy to deploy but are yet to see the rapid adoption. These include reducing how often soil is tilled, erosion control measures, soil mulching, maintaining ground cover, rotating crops, using different crop breeds, careful timing of grazing, and diversifying plants by including trees and shrubs amongst the crops.

All of these measures seek to increase and preserve the amount of SOM in the soils. As such, they improve fertility rates, make the soil more resilient to weather events, and secure the food supply by increasing the likelihood of a good harvest year after year. Soils also have the potential to be an important carbon sink. The 4 per 1000 initiative, launched at the Paris COP in 2015, champions increasing SOC content as a climate mitigation measure. A theoretical increase of just 0.4% of the world’s SOC would be greater than the increase in atmospheric CO2 experienced in 2015.


Heatwave kills ‘a third’ of spectacled fruit bats in Australia

Heatwave kills ‘a third’ of spectacled fruit bats in Australia

By Georgina Wade

Researchers from Western Sydney University have concluded that about 23,000 spectacled flying foxes, also known as spectacled fruit bats, died in a two-day heatwave in Northern Australia. Temperatures exceeded 42° C on 26 and 27 November, causing the bats to topple from trees into backyards, swimming pools and other locations. As rescuer David White put it, “it was totally depressing”.

And while the numbers already seem astronomical, they may not entirely representative of the devastation as some settlements were not included in the count. In fact, lead researcher Dr. Justin Welbergen believes the deaths could be as high as 30,000 deaths. He also sees the spectacled fruit bats as a “canary in the coal mine for climate change” because the events raise concerns regarding the fate of animals with more secretive and secluded lifestyles.

Experts have long been concerned about the survival of the spectacled flying foxes. Prior to November, government-backed statistics had estimated that only 75,000 spectacled flying foxes resided in Australia.

Mass deaths amongst the flying foxes used to be attributed to cyclones, but regularly occurring heatwaves have become a bigger, more formidable risk. National Flying Fox Programme Chairman, David Wescott, believes this is a major cause for concern, “it’s been a massive population decline for a species that isn’t under a great deal of pressure outside of these weather events,” he explains.

And the heat is not showing any signs of cooling down anytime soon. Just last week, Sydney experienced its hottest day since 1939 with temperatures reaching 47.3° C, resulting in rescuers working around the clock to save a number of koalas, birds and possums.

Nursing possums with burnt paws caused by hot roads and rehydrating birds that have fallen out of the sky are only some of the tasks rescuers are facing. Because, like the spectacled flying foxes, these native animals are particularly vulnerable to heat stress.

Kristie Harris, Office Manager for the New South Wales Wildlife Information, Rescue and Education Services (Wires) says responses like this are necessary as animals continue to succumb to heat extremes. “Any time we have any type of heat event, we know we’re going to have a lot of animals in need,” Harris said.


Cover photo from Max Pixel (public domain).
Arctic reindeer numbers decreasing due to climate change

Arctic reindeer numbers decreasing due to climate change

By Georgina Wade

A new report from the American Geophysical Research Union (AGU) finds that the population of caribou in the Arctic has crashed by more than half in the last two decades, falling from 5 million to around 2.1 million animals.

The findings reveal that changes in weather patterns and vegetation are making the Arctic tundra a much less hospitable place for the species. And while reindeer and caribou are the same species (caribou were never domesticated and tend to be much bigger), it’s the wild caribou herds in northern Canada and Alaska that are faring the worst. To date, herds have shrunk by more than 90 percent,a decline so drastic that “that recovery isn’t in sight”, the 2018 NOAA Arctic Report Card stated.

Prof Howard Epstein, an environmental scientist from the University of Virginia and one of the many scientists involved in the research behind the Arctic Report Card, warned that warming in the region shows no signs of abating. “We see increased drought in some areas due to climate warming, and the warming itself leads to a change in vegetation.”

Increases in the number of insects are also a problem. “If it’s warm and windy, the insects are oppressive, and these animals spend so much energy either getting the insects off of them or finding places where they can hide from insects,” Epstein explained.

And while carbon emissions can be reduced at a global scale in an attempt to limit the temperature increase and save the species, the growing pile of evidence suggests warming in the Arctic will continue. Additionally, scientists at AGU have revealed that East Antarctica’s glaciers have begun to “wake up” and show a response to the warming. NASA says that it has detected the first signs of significant melting in a swathe of glaciers in East Antarctica, adding to the mounting evidence of unprecedented climate-driven change at the top and bottom of the planet and signifying the opening of the “world’s freezer”.


Cover photo by Marcus Löfvenberg on Unsplash
Once eradicated mosquito-related diseases may return to Europe thanks to climate change

Once eradicated mosquito-related diseases may return to Europe thanks to climate change

By Will Bugler

Diseases including malaria, yellow fever, zika virus and dengue fever could return to Europe, according to the largest ever study of the mosquito evolutionary tree. The study investigates mosquito evolution over the last 195 million years and suggests that climate change today could provide favourable conditions for mosquito-borne diseases to spread in areas where they had been previously eradicated.

The research from the Milner Centre for Evolution at the University of Bath, University of York and China Agricultural University, shows that the rate at which new species of mosquitos evolve generally increases when levels of atmospheric carbon dioxide are higher. This is a concern because the greater the number of mosquito species, the more potential exists for new ways of transmitting disease, and perhaps for new variants of those diseases.

“It is important to look at the evolution of the mosquito against climate change because mosquitoes are responsive to CO2 levels” explained Dr Katie Davis, from the University of York’s Department of Biology, “Atmospheric CO2 levels are currently rising due to changes in the environment that are connected to human activity, so what does this mean for the mosquito and human health?

“Despite some uncertainties, we can now show that mosquito species are able to evolve and adapt to climate change in high numbers. With increased speciation, however, comes the added risk of disease increase and the return of certain diseases in countries that had eradicated them or never experienced them before.”

Chufei Tang, formerly at the Milner Centre for Evolution and now at the China Agricultural University, said “The rising atmospheric CO2 has been proven to influence various kinds of organisms, but this is the first time such impact has been found on insects.”

More research is needed to understand what climate change means for the future of the mosquito and the work will contribute to further discussions about the value of the mosquito to the ecosystem and how to manage the diseases they carry.


Tang et al (2018) “Elevated atmospheric CO2 promoted speciation in mosquitoes (Diptera, Culicidae)” is published in Communications Biology, DOI: 10.1038/s42003-018-0191-7. Click here to access the study.

Cover photo by U.S. Air Force/Nicholas J. De La Peña (public domain)
Biodiversity is plummeting, humanity needs a radical response

Biodiversity is plummeting, humanity needs a radical response

By Will Bugler

The scariest thing about Halloween this year? Digesting the findings of the World Wildlife Fund’s (WWF) most recent 2018 Living Planet report. The report shows that in the 40 short years between 1970 and 2014, more than 4,000 species of mammal, bird, fish reptile and amphibian are in decline. The average rate of decline of the species in the study? 60 percent. This astonishing loss of biodiversity presents a grave threat to human prosperity. The loss of wildlife and the ecosystems that support it will undermine any attempt to mitigate or adapt to climate change.

WWF’s report lists many factors for the decline, noting that just 25% of land on the planet has not been severely damaged by human activity. It also warns that this is likely to drop to just 10 percent by 2050 due to pollution, disease and climate change. The report was particularly striking in its timing, coming just weeks after the Intergovernmental Panel on Climate Change’s recent report on climate change, which warned of the impacts that the world faces at 1.5 degrees of warming. The impacts included wiping out almost all of the world’s coral reefs and altering other fragile habitats and ecosystems.

These two reports together show that significant and far reaching change is necessary in order to protect the vital systems that we rely on to grow food, access fresh water, and power our lives. They also clearly imply that only a holistic approach to climate change adaptation will be effective in safeguarding human systems in the coming decades.

Broadly speaking, the purpose of adapting to climate change is to safeguard lives and livelihoods of people in the face of considerable changes to the climate system; many of which are now inevitable. This goal becomes impossible if we are unable to protect the ecosystems that support life. These may seem like straightforward statements of the obvious, however this does have implications for the way we respond to climate change.

Decision making on climate adaptation should be part of a much broader approach to socio-ecological protection. When making decisions about how best to adapt to climate related impacts such as flooding for example, a narrow, impact-specific approach might be to identify the threat (an overflowing river) and then come up with a cost-effective way to reduce the risk it poses to people and property (a flood barrier perhaps). Congratulations you have successfully reduced the risk of flooding – but have you increased the overall resilience of the people and the environment?

The flood barrier might have diverted the flood risk further downstream leading to flooding of a fragile ecosystem or farmland. It may have cut off vulnerable populations from accessing the market to sell their goods or reduced access to the river for fishermen, or it may provide a perverse incentive for people to build houses and property behind the barrier, increasing the potential impact of a future, more severe flood event.

Finding solutions to climate change that build long-term resilience, requires decisions that are taken in line with a coherent, systemic approach to strengthening ecosystems and protecting the lives of the most vulnerable people. Decisions that reduce climate risk or indeed cut carbon emission at the expense of either people or the environment are self-defeating.

Download the full WWF Living Planet Report by clicking here.


Cover photo by Thomas Kelley on Unsplash
Japanese cherry blossoms make early appearance: Extreme weather to blame

Japanese cherry blossoms make early appearance: Extreme weather to blame

By Georgina Wade

The annual cherry blossom bloom in Japan signals the arrival of spring. Typically occurring in early April, the event brings flocks of tourist to the region looking to experience the floral embodiment of Japan’s most deep-rooted cultural and philosophical beliefs. But never has there been a widespread cherry blossom show put on in the fall – until now. Weathernews received more than 350 reports of early blossoms.

But, what is causing this premature fall bloom? According to the Hiroyuki Wada, an arborist with the Flower Association of Japan, cherry blossom buds develop during summer but usually don’t bloom until because of a plant hormone the leaves release to slow plant growth in preparation for the winter. However, Japan was hit by both Typhoon Jebi and Typhoon Trami in September, which carried powerful winds and salty seawater, forcing trees to shed leaves before the hormone could be released, and with the additional warm air from the South, the trees were ‘tricked’ to blossom.

Category 5 Typhoon Jebi was the strongest storm to hit Japan since 1993, killing 17 people with insured losses estimated at between 2.3 and 4.5 billion USD. A few weeks later, Typhoon Trami followed suit leaving dozens injured and hundreds of thousands of homes without power. Warm air brought about by the typhoons was quickly masked by cooler conditions during the storms’ aftermath, prompting a combination of changeable weather that mimicked spring.

Although it’s clear that this year’s storm season is to blame, the premature cherry blossoming trend has been ongoing for some time. For over 1,000 years, the flowering of Japan’s cherry trees has been chronicled in the city of Kyoto. But bloom dates have shifted radically earlier in recent decades, signalling that the region is warming.

Yasuyuki Ano, a professor of environmental sciences at Osaka Prefecture University, assembled a data set that compiles blossom-flowering dates in Kyoto starting from 800 A.D. Prior to 1850, flowering dates were fairly stable.

But from 1850 to present day, the flowering period has only surged forward at the rate of about one week per century. With warmer March temperatures typically signifying an earlier bloom, scientists believe the earlier bloom dates are directly linked with rising regional temperatures. Both Kyoto’s cherry tree flowering and temperature data suggest that its climate is the warmest it has been in at least a millennium.

The buds that opened now will not be blossoming again in coming spring. Despite this early blooming, experts do not believe this event will disrupt the timing or magnificence of the bloom next spring.


Cover photo by Sora Sagano on Unsplash.
Protecting wetlands helps communities reduce damage from hurricanes and storms

Protecting wetlands helps communities reduce damage from hurricanes and storms

By Siddharth Narayan, University of California, Santa Cruz and Michael Beck, University of California, Santa Cruz

2017 was the worst year on record for hurricane damage in Texas, Florida and the Caribbean from Harvey, Irma and Maria. We had hoped for a reprieve this year, but less than a month after Hurricane Florence devastated communities across the Carolinas, Hurricane Michael has struck Florida.

Coastlines are being developed rapidly and intensely in the United States and worldwide. The population of central and south Florida, for example, has grown by 6 million since 1990. Many of these cities and towns face the brunt of damage from hurricanes. In addition, rapid coastal development is destroying natural ecosystems like marshes, mangroves, oyster reefs and coral reefs – resources that help protect us from catastrophes.

In a unique partnership funded by Lloyd’s of London, we worked with colleagues in academia, environmental organizations and the insurance industry to calculate the financial benefits that coastal wetlands provide by reducing storm surge damages from hurricanes. Our study, published in 2017, found that this function is enormously valuable to local communities. It offers new evidence that protecting natural ecosystems is an effective way to reduce risks from coastal storms and flooding.

Coastal wetlands and flood damage reduction: A collaboration between academia, conservation and the risk industry.

The economic value of flood protection from wetlands

Although there is broad understanding that wetlands can protect coastlines, researchers have not explicitly measured how and where these benefits translate into dollar values in terms of reduced risks to people and property. To answer this question, our group worked with experts who understand risk best: insurers and risk modelers.

Using the industry’s storm surge models, we compared the flooding and property damages that occurred with wetlands present during Hurricane Sandy to the damages that would have occurred if these wetlands were lost. First we compared the extent and severity of flooding during Sandy to the flooding that would have happened in a scenario where all coastal wetlands were lost. Then, using high-resolution data on assets in the flooded locations, we measured the property damages for both simulations. The difference in damages – with wetlands and without – gave us an estimate of damages avoided due to the presence of these ecosystems.

Our paper shows that during Hurricane Sandy in 2012, coastal wetlands prevented more than US$625 million in direct property damages by buffering coasts against its storm surge. Across 12 coastal states from Maine to North Carolina, wetlands and marshes reduced damages by an average of 11 percent.

These benefits varied widely by location at the local and state level. In Maryland, wetlands reduced damages by 30 percent. In highly urban areas like New York and New Jersey, they provided hundreds of millions of dollars in flood protection.

Wetland benefits for flood damage reduction during Sandy (redder areas benefited more from having wetlands). Narayan et al., Nature Scientific Reports 7, 9463 (2017)., CC BY

Wetlands reduced damages in most locations, but not everywhere. In some parts of North Carolina and the Chesapeake Bay, wetlands redirected the surge in ways that protected properties directly behind them, but caused greater flooding to other properties, mainly in front of the marshes. Just as we would not build in front of a seawall or a levee, it is important to be aware of the impacts of building near wetlands.

Wetlands reduce flood losses from storms every year, not just during single catastrophic events. We examined the effects of marshes across 2,000 storms in Barnegat Bay, New Jersey. These marshes reduced flood losses annually by an average of 16 percent, and up to 70 percent in some locations.

Reductions in annual flood losses to properties that have a marsh in front (blue) versus properties that have lost the marshes in front (orange). Narayan et al., Nature Scientific Reports 7, 9463 (2017)., CC BY

In related research, our team has also shown that coastal ecosystems can be highly cost-effective for risk reduction and adaptation along the U.S. Gulf Coast, particularly as part of a portfolio of green (natural) and gray (engineered) solutions.

Reducing risk through conservation

Our research shows that we can measure the reduction in flood risks that coastal ecosystems provide. This is a central concern for the risk and insurance industry and for coastal managers. We have shown that these risk reduction benefits are significant, and that there is a strong case for conserving and protecting our coastal ecosystems.

The next step is to use these benefits to create incentives for wetland conservation and restoration. Homeowners and municipalities could receive reductions on insurance premiums for managing wetlands. Post-storm spending should include more support for this natural infrastructure. And new financial tools such as resilience bonds, which provide incentives for investing in measures that reduce risk, could support wetland restoration efforts too.

Improving long-term resilience

The dense vegetation and shallow waters within wetlands can slow the advance of storm surge and dissipate wave energy. USACE

Increasingly, communities are also beginning to consider ways to improve long-term resilience as they assess their recovery options.

There is often a strong desire to return to the status quo after a disaster. More often than not, this means rebuilding seawalls and concrete barriers. But these structures are expensive, will need constant upgrades as as sea levels rise, and can damage coastal ecosystems.

Even after suffering years of damage, Florida’s mangrove wetlands and coral reefs play crucial roles in protecting the state from hurricane surges and waves. And yet, over the last six decades urban development has eliminated half of Florida’s historic mangrove habitat. Losses are still occurring across the state from the Keys to Tampa Bay and Miami.

Protecting and nurturing these natural first lines of defense could help Florida homeowners reduce property damage during future storms. In the past two years our team has worked with the private sector and government agencies to help translate these risk reduction benefits into action for rebuilding natural defenses.

Across the United States, the Caribbean and Southeast Asia, coastal communities face a crucial question: Can they rebuild in ways that make them better prepared for the next storm, while also conserving the natural resources that make these locations so valuable? Our work shows that the answer is yes.


This is an updated version of an article originally published on Sept. 25, 2017.The Conversation Siddharth Narayan, Postdoctoral Fellow, Coastal Flood Risk, University of California, Santa Cruz and Michael Beck, Research professor, University of California, Santa Cruz. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cover photo by NPS Everglades/Flickr (public domain)
Australian ecosystems crippling under weight of climate change

Australian ecosystems crippling under weight of climate change

By Georgina Wade

­­Ecosystems across Australia are on the brink of collapse under climate change. Research published in Nature Climate Change analysing the interaction of gradual climate trends and extreme weather events since the turn of the century describes a series of sudden and catastrophic ecosystem shifts that have occurred recently across Australia.

Amongst the most notable tragedies, a mass mortality of corals on the Great Barrier Reef occurred in 2016 after 30% of the reef’s corals died in a relentless nine-month marine heatwave with an additional 20% bleached to death in 2017. And with Australia’s average sea temperature having increased by about 1°C since the start of the 19th century and continuing to climb, the remaining corals face the same fate.

Australia is one of the most climatically variable places in the world. In a study from Environmental Research Letters, Australia showed the highest inter-annual variability of any continent and also showed the highest biome-level variability of any continent for tropical forest, temperature broadleaf forest, and tropical savannas and grasslands.

And despite being a highly populous region involving numerous activities that transform the natural landscape, Australia retains large tracts of near-pristine natural systems.

Many of these regions are iconic, providing benefits to the tourism industry and sustaining outdoor activities while providing precious ecological services. In spite of this, the stress of climate change and extreme weather events is causing environmental alterations in these valuable ecosystems.

The research examined several ecosystems across Australia that have experienced catastrophic changes in the last decade and found that undisturbed systems are not necessarily more resilient to climate change.

Describing a combination of “presses” and “pulses” in which gradual climate change can be thought of as an ongoing “press” on which the “pulse” of extreme events is now superimposed, the case studies provide a range of examples in which both can interact to push an ecosystem to a “tipping point”.

The difficulty in foreseeing the timing and severity of extreme weather events makes predicting ecosystem collapses essentially impossible. Additionally, the cost of targeted interventions can be exorbitant.

Between the uncertainty and associated costs, interventions are difficult to implement and might even require controversial methods like assisted colonisation. Ecosystem management will not only require high policy and philosophy fluidity, but decisions will increasingly need to be made faster and potentially without fully understanding ecological and evolutionary consequences.


Harris, R.M.B et al. (2018). Biological responses to the press and pulse of climate trends and extreme events. Nature Climate Change, Vol. 8, pages 579–587 (2018).

Cover photo Wikimedia Commons (CC BY-SA 3.0): Bleached branching coral (foreground) and normal branching coral (background). Keppel Islands, Great Barrier Reef.
Arctic ice depends on half a degree of heat

Arctic ice depends on half a degree of heat

By Tim Radford

Half a degree Celsius doesn’t sound like much, but for the Arctic ice it could make a world of difference.

Two separate studies have calculated what it would take to keep the Arctic ice frozen through the summer months – and thus preserve the precious polar ecosystem and help contain further global warming.

It’s simple: fulfil the promises that 195 nations made in Paris in 2015, and keep global warming to “well below 2°C” and ideally at 1.5°C by the year 2100.

That extra half a degree makes a huge difference. At a maximum global average warming of 2°C above the norm for most of human history, the Arctic could become technically ice-free once every three to five years.

Reduce carbon dioxide emissions even further, take greater steps to conserve forests and keep the global temperature at the 1.5° C maximum rise, and the chances are that the Arctic seaways will open only about one summer in 40 years.

Glaciologists consider the Arctic “ice-free” when there are only a million square kilometres of floe left. It has yet to happen. But the sea ice has become noticeably thinner, and smaller in surface area, over the last 40 years.

“The good news is that the sea has a quick response time and could theoretically recover if we brought down global temperatures . . . though  other ecosystems could see permanent negative impacts from ice loss”

For more than two decades, meteorologists and oceanographers have repeatedly warned that runaway global warming, as a consequence of ever-greater combustion of fossil fuels, could bring about an ice-free polar ocean by about 2050.

Sea ice is part of the climate machine. It reflects solar radiation and keeps the ocean cool. It provides a surface on which Arctic seals can haul out, and on which polar bears can feed.

But the catch is that, although the world’s nations almost unanimously voted in Paris to contain global warming, the pledges made at the time were nowhere near ambitious enough.

Since the Paris meeting global warming has accelerated, and one group has warned that the 1.5°C limit could be exceeded by 2026. Many researchers think that the political decisions of the next decade will be vital.

Clear benefits

Researchers already know that the 1.5°C target will deliver palpable rewards: it will make a huge difference, for instance, to sea levels, grain harvests and global fish catches.

US and Canadian climate scientists set out to see what difference half a degree would make to the Arctic. They worked with different climate simulations to reach roughly the same conclusion, in two papers in the journal Nature Climate Change.

The Canadian team calculated that at 2°C, ice-free conditions would happen every five years; at 1.5°C, the hazard would drop to one in 40 years; at 3°C, permanent ice-free summers would be likely. A second study from the US backed up the premise.

“I didn’t expect to find that half a degree Celsius would make a big difference, but it really does,” said Alexandra Jahn, of the University of Colorado at Boulder.

Higher costs

“At 1.5°C half the time we stay within our current summer sea ice regime, whereas if we reach two degrees of warming, the summer sea ice will always be below what we have experienced in recent decades.”

Higher levels of warming would impose higher costs: 4°C of warming would deliver a high probability of an ocean free of ice for three months every summer by 2050, and five months a year by 2100.

“The good news is that the sea has a quick response time and could theoretically recover if we brought down global temperatures at any point in the future,” Dr Jahn said.

“In the meantime, though, other ecosystems could see permanent negative impacts from ice loss, and those can’t necessarily bounce back.”


This article was originally published on Climate News Network and can be accessed here.

Cover photo by Anders Jildén on Unsplash.