Mass die-offs from climate crisis will happen soon unless urgent action is taken

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Mass die-offs from climate crisis will happen soon unless urgent action is taken

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OUR BURNING PLANET

By Tony Carnie• 9 April 2020

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Though large creatures such as the Southern Right Whale can migrate over vast distances, they are part of a complex marine food

Just as governments have scrambled at the last minute to seal their borders against the coronavirus crisis, a similar sense of urgency is needed to delay the impending risk of ‘sudden and severe’ impacts of the climate crisis, scientists warned on Wednesday.

There are still widespread perceptions that the more severe effects of climate change may only manifest themselves gradually towards the end of the century.

But a new study in the leading science journal Nature suggests that serious disruptions to critical elements of the global ecology (and the people who depend on it) may begin far more abruptly than anticipated – conceivably within the next 10 years unless concerted action is taken to “flatten the [climate change] curve”.

Lead author Dr Christopher Trisos from the University of Cape Town suggests that under a scenario of continued high carbon emissions, such abrupt events – including “catastrophic” multi-species die-offs of land and sea creatures – could begin even before 2030 in the tropical oceans off Africa and then spread to tropical forests and higher latitudes by 2050.

Trisos, a Rhodes Scholar and senior researcher at the UCT’s African Climate and Development Initiative, and fellow authors Dr Cory Merow (University of Connecticut) and Dr Alex Pigot (University College London), say that the summarised nature of several climate change projections can mask the abrupt impacts at particular locations.

Citing a number of studies at a more localised level, they say that temperature warming over recent decades has already been associated with marked population declines and local extinctions of some species.

“At the very least, our results show that within 30 years, continued high emissions will drive a sudden shift across many ecological assemblages to climate conditions under which we have almost no knowledge of the ability of their constituent species to survive,” they say.

Ecological assemblages are groups of creatures or plants which live in the same area and interact closely through distinct relationships such as pollination or eating each other.

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Marine organisms, especially seagrasses, corals, cephalopods, reptiles and sea mammals appear to be most vulnerable to abrupt climate changes. Catastrophic, multi-species coral die-offs caused by a record-breaking marine heatwave in 2016 are one recent example. (Photo: Steve Benjamin / WILDOCEANS)

Trisos and his colleagues say that if global warming is kept below 2°C, less than 2% of these assemblages globally are projected to undergo abrupt exposure events of more than 20% of their constituent species. However, the risk accelerates with the magnitude of warming, threatening 15% of assemblages at 4°C.

“This near-simultaneous exposure among multiple species could have sudden and devastating effects on local biodiversity and ecosystem services. Catastrophic, multi-species coral die-offs caused by a record-breaking marine heatwave in 2016 are one recent example.”

To conduct the study, Trisos and his colleagues used a database of more than 30,000 species, including birds, mammals, reptiles, amphibians, marine fish, krill, corals and seagrasses, and more than 20 climate models projecting rainfall and mean temperature increases of between 1.75°C and 4.4°C before the end of the century.

However, reducing greenhouse gas emissions and delaying the onset of exposure to dangerous climate conditions — even by a few decades — could buy valuable time for ecological assemblages to adapt, potentially reducing the magnitude of ecological disruption.

In their study, they looked at the distinct ecological niches shaped by suitable temperature or moisture ranges to demarcate the historical climate boundaries of the species studied.

“For each species at a site [that is, in a 100km grid cell], we defined the local species exposure time as the year after which projected local temperatures consistently exceed – for at least five years – the maximum temperature experienced by the species across its geographic range during historical climate projections (1850–2005).”

Under high emission scenarios of 4.4°C, they project that 81% of land and 37% of sea group would have at least one species exposed to unprecedented temperatures beyond historical niche limits before 2100.

Marine organisms, especially seagrasses, corals, cephalopods, marine reptiles and marine mammals, appeared to be most vulnerable to abrupt changes.

Evidence from laboratory and field studies also suggests that the onset of unprecedented climate change can result in local extinctions.

The abruptness of exposure to climate change also varied by location, but some of the places most likely to be affected first included the Sahel region in north Africa, the Amazon, India, northern Australia and tropical oceans.

“In some locations – such as the Caribbean and the Coral Triangle – exposure is predicted to be underway already, with these hot spots of exposure expanding in spatial extent over time.

“By 2050, exposure spreads beyond ocean ecosystems to iconic terrestrial ecosystems, such as the Amazon, Indonesian and Congolese rainforests.”

In a separate statement issued by the University of Cape Town, Trisos said: “Billions of people depend on ecosystems for their livelihoods and vital nutrition. We fish on coral reefs. We depend on eco-tourism. We rely on healthy forests for carbon storage and water filtration.

“If there is a sudden collapse of these ecosystems in a single decade, you could lose most or all of these services. Your income is at risk. Your food security is at risk. Your mental and spiritual well-being could be at risk if those ecosystems are important for you culturally,” said Trisos.

In South Africa, several places were at particular risk of abrupt disruption to biodiversity in a high-emissions scenario, including the coast from Cape Agulhas to Mozambique, inland areas on the western side of the Western Cape up to the Namibian border, the entire Northern Cape and parts of the Free State.

Trisos said he hoped that the research would be a serious wake-up call for policymakers and other key players.

“I’m hoping that by showing how terrifyingly widespread and close in time the risk is for biodiversity globally, this will help lead us towards positive tipping points in our response to divest from fossil fuel and transition to renewable energy.”

Dr Christopher Trisos, a senior researcher at the African Climate and Development Initiative at the University of Cape Town focuses on the intersection of climate change, biodiversity and human well-being. He was a co-ordinating lead author for the Africa region of the Intergovernmental Panel on Climate Change (IPCC), 6th Assessment Report. He is also a Rhodes Scholar and graduate of Oxford University.


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Climate change could cause abrupt biodiversity losses this century

April 9, 2020 | Christopher Trisos, Senior Research Fellow, University of Cape Town - Alex Pigot, Research Fellow Genetics, Evolution & Environment Div of Biosciences, UCL

The impacts of climate change on species and ecosystems are already evident. Poleward shifts in the geographic distributions of species, catastrophic forest fires and mass bleaching of coral reefs all bear the fingerprints of climate change.

But what will the world’s biodiversity look like in the future?

Projections indicate that unless emissions are rapidly reduced the climate crisis will get substantially worse. Up to 50% of species are forecast to lose most of their suitable climate conditions by 2100 under the highest greenhouse gas emissions scenario.

But we still lack answers to some basic questions. When will species be exposed to potentially dangerous climate conditions? Will this occur in the next decade or only later in the century? Will the exposure of species accumulate gradually, one species at a time? Or should we expect abrupt jumps as the climate limits of multiple species are exceeded?

Our understanding of when and how abruptly climate driven disruptions of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future. We took a different route. We used annual projections of temperature and precipitation from 1850 to 2100 across more than 30,000 marine and terrestrial species to estimate the timing of species exposure to potentially dangerous climate conditions.

Based on these projections, we estimate that climate change could cause sudden biodiversity losses. These could occur much sooner this century than had been expected. This new analysis indicates that a high percentage of species in local ecosystems could be exposed to potentially dangerous climate conditions simultaneously.

Rather than slowly sliding down a climate change slope, many ecosystems face a cliff edge.

Risk of abrupt biodiversity loss early this century

Abrupt biodiversity loss due to marine heatwaves that bleach coral reefs is already under way in tropical oceans. The risk of climate change causing sudden collapses of ocean ecosystems is projected to escalate further in the 2030s and 2040s. Under a high greenhouse gas emissions scenario the risk of abrupt biodiversity loss is projected to spread onto land, affecting tropical forests and more temperate ecosystems by the 2050s.

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Biodiversity exposure to dangerous climate conditions.
These dire projections use historical temperature models to find the upper limit that each species can survive under, as far as we know. Once temperatures rise to levels a species has never experienced, scientists have very limited evidence of their ability to survive.

It’s possible some species, such as those with very short generation times, may be able to adapt. For species with longer generation times – such as most birds and mammals – it may be only a few generations before unprecedented temperatures occur. When this happens the species’ ability to evolve out of this problem may be limited.

Why it matters

Abrupt losses of biodiversity from climate change represent a significant threat to human well-being. In many countries a large percentage of people rely on their immediate natural environment for their food security and income. Sudden disruption of local ecosystems would negatively affect their ability to earn an income and feed themselves, potentially pushing them into poverty.

For instance, marine ecosystems in the Indo-Pacific, Caribbean and the west coast of Africa are at high risk of sudden disruption as early as the 2030s. Hundreds of millions of people across these regions rely on wild-caught fish as an essential source of food. Eco-tourism revenues from coral reefs are also a major source of income.

In Latin America, Asia and Africa, large parts of the Andes, Amazon, Indonesian and Congo forests are projected to be at risk from 2050 under a high emissions scenario.

Sudden loss of animal communities could negatively affect the food security of people in these regions. It could also reduce the long-term ability of tropical forests to lock up carbon if the birds and mammals that are important for dispersing seeds are lost.

Urgent next steps

These findings highlight the urgent need for climate change mitigation. Rapidly reducing greenhouse gas emissions this decade will help save thousands of species from extinction, and protect the life-giving benefits they provide to humans.

Keeping global warming below 2°C flattens the curve of climate change risk to biodiversity. It does this by massively reducing the number of species at risk and buys more time for species and ecosystems to adapt to the changing climate – whether that’s by finding new habitats, changing their behaviour, or with the help of human-led conservation efforts.

There’s also an urgent need to ramp up efforts to help people in high risk regions adapt their livelihoods as climate change alters local ecosystems.

Projecting where and when species will be exposed to dangerous climate change throughout the century could provide an early warning system, identifying those areas most at risk of abrupt ecological disruption. In addition to highlighting the urgent need for reducing fossil fuel usage, these results could help guide conservation efforts, such as designating new protected areas in climate refugia.

They could also inform resilient ecosystem-based approaches for helping people adapt to changing climates. An example would be planting mangroves to protect coastal communities against increasing flooding. The potential to continuously update and validate these near-term projections as ecological responses to climate change unfold should further refine projections of future climate risks to biodiversity that are so central to managing the climate crisis.

Our planet is still teeming with life. And with the right political leadership and daily actions that we take as citizens, we still have the power to keep it that way.


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Vulnerable lizard species gets hot and bothered in rising temperatures

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Sungazer lizard/ Image: Flickr

By Juan Scheun, Andre Ganswindt and Trevor McIntyre | 16 Nov 2021

Reptiles probably don’t spring to mind when you think of species likely to be affected by rising global temperatures. After all, since they’re often found in hot environments, they’re able to withstand high temperatures and can reduce water loss through their skin.
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Despite the ability to withstand high temperatures within their environment, reptiles depend on access to specific thermal environments to optimise various bodily functions. These include metabolism – converting food to energy – and reproduction. That means significant increases in temperature of the kind being increasingly recorded in many parts of the world could potentially have a negative effect on reptiles.

Although more than 1600 of the 9400 reptile species globally can be found on the African continent, there has been almost no research conducted on the effect of climate change on African reptiles. This is partly because of the evasive nature of many reptile species, and also because funding is limited.

To start filling this knowledge gap, we studied how higher temperatures affect the sungazer lizard (Smaug giganteus). These charismatic reptiles are endemic to South Africa’s highveld. They are already threatened by habitat destruction and illegal collection for the pet and traditional medicine trades. Captive breeding attempts have not worked, which sets the species back further.

We wanted to know what higher temperatures in South Africa will mean for endemic species like the sungazer lizard. Specifically, we wanted to test how being exposed to higher temperatures affected the lizards’ adrenocortical activity as seen in glucocorticoid secretion. Once an animal is exposed to a possible stressor, such as elevated temperatures, the physiological stress response is activated. The animal then secretes more glucocorticoids.

One of this hormone’s primary functions is to provide the required energy and behaviour responses to ensure survival. An elevation in glucocorticoids is adaptive in the short term. But prolonged exposure to elevated levels can have negative effects. These include the suppression of reproductive and immune systems and overall reduced survival. By quantifying an animal’s glucocorticoid levels, scientists can learn crucial information about physiological stress and chances of survival.

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Sungazer lizard/ Image: Flickr

Experiments

Animals’ bodies respond in various ways to stressors like the presence of a predator, an injury, or a change of surroundings. Physiological responses allow an organism to produce sufficient energy or maintain water balance to escape or recover from a stressful situation. A temporary increase in the secretion of glucocorticoids from the adrenal gland is just one form of response.

Once in the bloodstream, glucocorticoids are heavily metabolised in the liver; the hormone metabolites move to the bile before being excreted in faeces. As such, faecal glucocorticoid metabolites can be monitored as a robust proxy for an individual’s adrenocortical activity. Faecal collection also requires almost no direct human-animal interaction, so it’s non-invasive for the animals.

Our research was conducted in a captive environment, at the National Zoological Garden in Pretoria. Because the species is already vulnerable and there aren’t many available to researchers, we only studied four female and two male animals.

At the National Zoological Garden animals are kept at 27℃-30℃, which is thought to be the ideal range for the species. In the wild they will, of course, experience a wider range of temperatures, depending on the season. For now, though, these will rarely reach the 39℃ we used as our high point here.

We divided the animals equally into a control and an experimental group. We let them get used to their new surroundings, at a temperature of 30℃ for two weeks. Control animals were then kept at 30℃ for another six weeks; the experimental group were kept at 39℃ for the same time. Finally, both groups were kept at 30℃ for a further three weeks. Study animals were monitored by conservation staff throughout the study to ensure they were safe and healthy.

We collected faecal samples from all study animals daily and quantified their faecal glucocorticoid metabolites (fGCM). Females kept at constant temperatures showed a constant fGCM pattern throughout the study period. Those subjected to higher temperatures showed a sudden spike in fGCM levels immediately following an increase in temperature, as well as during the return period to 30℃.

The male kept at constant temperatures did not show consistent fGCM levels during the study period. The male exposed to higher temperatures, meanwhile, showed a steady increase in fGCM levels as the study progressed.

These results tell us several things. First, the sudden peak in fGCM levels in test females following temperature manipulations suggests the animals perceived the sudden change in environmental temperatures as a stressor. It activated their physiological stress response to restore homeostasis and ensure survival.

This response in female sungazer lizards may be interpreted positively: it could potentially help them to survive in environments where temperatures rise significantly.

The test male’s story is less positive, as he showed increased adrenocortical activity throughout the study period, even when temperatures returned to 30℃. This could indicate that male sungazer lizards are sensitive to any temperature elevation in their immediate environment, despite only displaying a gradual moderate increase in excreted hormone metabolite levels.

More to understand

We do not want to make substantial inferences, particularly given the small number of lizards we were able to test. But these findings suggest there are sex-specific differences in stress responses within the species – and a potential further threat to sungazer lizard populations likely to be subjected to higher temperatures in future.

Follow-up studies will be needed. For instance, stress responses should be monitored in wild sungazer lizard populations. It’s also important to remember that different species will react differently to climate change, so more reptile species will need to be studied. DM/ML

Dr Robert Campbell, a wildlife veterinarian, co-authored the study this article is based on.

This story was first published in The Conversation.

Juan Scheun is a postdoctoral fellow at the University of South Africa. Andre Ganswindt is a professor and Director of the Mammal Research Institute at the University of Pretoria. Trevor McIntyre is an associate professor in Zoology at the University of South Africa.


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Warning to KZN: Cyclone Ana highlights climate risks faced by vulnerable populations

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Debris and destroyed and damaged buildings in a residential neighbourhood in Beira, Mozambique, after Cyclone Idai hit in March 2019. (Photo: Guillem Sartorio / Bloomberg via Getty Images)

By Ethan van Diemen | 27 Jan 2022

As Madagascar, Malawi and Mozambique mop up after Cyclone Ana, scientists caution that South Africa’s east coast could be hit by intense tropical cyclones.
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Now, because of global warming, there is much more energy available for tropical cyclones to become intense.

“My analysis is, and the assessment of the Global Change Institute is, that the risks exist for such an intense tropical cyclone to make landfall in South Africa. It will bring complete chaos and destruction as we’ve never seen before. We will not know what to do when such a cyclone strikes Richards Bay or if it strikes Maputo and then moves westward along the Limpopo River Valley or along the boundary of SA and Zimbabwe.

“The point is that northeastern South Africa is, for the first time in recorded history, at risk of a Category Three to Category Five hurricane making landfall. The flooding will be enormous. The risk to life will be tremendous for communities living near the rivers in the northeast. We will not be used to 200km/h winds and vulnerable people in informal settlements will have their roofs and walls ripped off.” DM/OBP


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Climate change and wildlife – three studies that reveal the devastating toll on Africa’s animals

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The carcass of a Grévy’s zebra, an endangered species which exists only in the northern part of Kenya, where drought is ongoing. (Photo: Fredrik Lerneryd / AFP)

By Moina Spooner | 18 Nov 2022

Academics have sounded the alarm on the effects of climate change on wildlife.
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Climate change has produced a number of threats to wildlife. Over time, changing rainfall patterns have transformed habitats and forced animals to move. Increasing temperatures are causing mass die-off events during heatwaves and making it hard for animals to find food.

Drought is recurring in parts of the continent. The increased frequency means there’s little or no time to recover before the next one occurs. The wildlife in some of these regions lives alongside people who are also struggling to survive and keep their livestock alive. This puts people and wildlife into conflict as they compete for diminishing sources of water and food.

Climate change can also strongly influence the physiology, behaviour and breeding success of animals.

Academics writing for The Conversation Africa have covered some of these issues. Their articles and research sound a warning bell on the effects of climate change on wildlife. Here we share three of these important reads.

Drought takes a toll on East Africa’s wildlife

Over the past two decades, the Horn of Africa – specifically Ethiopia, Somalia and Kenya – has experienced more intense and frequent droughts. Drought adds to the pressure on resources like water and pasture. This makes livestock and wildlife more susceptible to malnutrition, disease, mass mortalities and competition with each other over resources.

Kenyan scientist and conservationist Abdullahi Ali has worked for over 15 years along the volatile Kenya-Somalia border region. He’s seen at first hand the devastating effect that these droughts have on wildlife and habitat. For instance, based on monitoring herds, he’s recorded the deaths of 30 endangered hirola (about 6% of the global population) as a direct consequence of drought over the past year.

Ali is concerned that droughts are recurring. Their increased frequency means there’s little or no time to recover before the next drought.

Warmer temperatures, fruit trees and forest elephants

Gabon is home to some of the highest densities of forest elephants. Many of them live in Lopé National Park, a 5,000km² protected area.

Ecological experts Katharine Abernethy, Emma Bush and Robin Whytock have observed a significant drop in the physical condition of these elephants – an 11% decline since 2008.

This corresponds with a massive collapse in tree fruiting events. Elephants are much less likely than before to find ripe fruit. On average, elephants would have found ripe fruit on one in every 10 trees in the 1980s, but need to search more than 50 trees today.

The collapse in tree fruiting events is attributed to warmer temperatures. Lopé tree species depend on a critical drop in night-time temperatures during the long dry season to trigger flowering. In years when temperatures in the dry season did not dip below 19ºC these species produced no fruit.

So, even where forest elephants and other large animals are relatively well protected from threats such as hunting, global human pressures – such as the climate crisis – could affect their survival.

The loss of the Kalahari’s hornbills

For birds in arid zones, rising temperatures pose a significant problem. They usually breed in response to rainfall, which often occurs during the hottest time of the year. And birds are mostly active during the day, when they are exposed to the sun’s heat. This is when their vital processes for reproduction take place – such as territorial defence, courtship, finding food for their young and attending the nest.

Ornithology expert Nicholas Pattinson assessed the effects of air temperature and drought on the breeding output of southern yellow-billed hornbills in southern Africa’s Kalahari Desert over a decade, from 2008 to 2019.

His study found that breeding output fell when air temperatures rose in the breeding season. Breeding attempts all failed when average daily maximum air temperatures exceeded 35.7°C.

In the Kalahari, air temperatures have already risen more than 2°C in a few decades. At this rate, by 2027, these birds will not breed at all at this site. They will quickly become locally extinct.

Moina Spooner, Assistant Editor, The Conversation.

This article is republished from The Conversation under a Creative Commons licence.


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