Man-made climate change increases extinction dangers

Man-made climate change increases extinction dangers

New research warns that the survival of a sizeable proportion of life on Earth is being put at risk as fossil fuel emissions push up global temperatures.

LONDON, 2 May, 2015 – Climate change threatens one in six of the world’s species with extinction, according to new research.

The higher the average rise in planetary temperatures because of man-made global warming, the faster the rate of biodiversity loss − and the greater the survival dangers for a significant proportion of life on Earth.

Two studies published on the same day in the same journal reach the same conclusion: that climate change from any cause is bad for an ecosystem’s health and presents dangers of species extinction.

That the natural world is responding uneasily to man-made, or anthropogenic, climate change is not in doubt. In the last two years, scientists have shown that it can be the last straw for a population already under pressure, or so vulnerable it can no longer survive without human help.

Change habitat

It can change the habitat and climate in which plants and animals have evolved, but offer no safe place to which to migrate, and it can provide the conditions for new threats to flourish.

Genomic evidence shows that, in the recent past, it can constrict the numbers available for breeding, and ancient palaeontological evidence has linked greenhouse gas concentrations to catastrophic mass extinction.

Mark Urban, professor of ecology and evolutionary biology at the University of Connecticut, US, now reports in the journal Science that a comprehensive look at the whole picture tells the same story.

His warning is that if fossil fuel emissions continue on the business-as-usual scenario, and temperatures on average reach the predicted 4.3°C increase, then one in six of the world’s species could face extinction.

“We believe the past can inform the way we plan our conservation efforts”

There are problems with this kind of research: more than a million species have been described and named, but nobody knows, to an order of magnitude, how many species there might actually be on the planet. The living world is still largely unknown.

So Dr Urban surveyed 131 published predictions of extinction, and then subjected them to a mathematical technique called meta-analysis.

Extinction risks were higher in South America, Australia and New Zealand − all places that harboured diverse assemblies of endemic species with small ranges and,  in the case of the large islands, not a lot of choice about places to which to migrate.

“Extinction risks from climate change are expected not only to increase but to accelerate for every degree rise in global temperatures,” he concludes. “The signal of climate change-induced extinctions will become increasingly apparent if we do not act now to limit future climate change.”

Seth Finnegan, a biologist at the University of California Berkeley, and colleagues report in Science that they looked at the marine fossil record during the climate ups and downs of the last 23 million years.

They identified 2,897 different fossil genera from six major groups – marine mammals such as seals and whales, sharks, bivalves, gastropods or snails, echinoids and corals – and used the evidence to arrive at a baseline for a “natural” extinction risk that could not be blamed on humans.

Vulnerable species

“Our goal was to diagnose which species are vulnerable in the modern world, using the past as a guide,” Dr Finnegan says.

“We believe the past can inform the way we plan our conservation efforts. However, there is a lot more work that needs to be done to understand the causes underlying these patterns and their policy implications.”

Not surprisingly, those vertebrates with small geographic ranges were at the highest risk − with whales, dolphins and seals more likely to face extinction than invertebrates such as sharks and corals.

The tropical waters of the west Atlantic and the west Pacific provided the most vulnerable ecosystems in the last 23 million years, and these regions today are predicted to experience the fastest rates of climate change and the greatest human impact in the shape of habitat destruction, overfishing and pollution.

The researchers also established another measure of extinction risk: in terms of species survival, it is 10 times more perilous to be a mammal than a clam. – Climate News Network

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High anxiety that mountain peaks are warming faster

High anxiety that mountain peaks are warming faster

Scientists call for international efforts to determine why temperatures on high-altitude mountains appear to be rising faster than in nearby lowlands.

LONDON, 28 April, 2015 − Temperatures could be climbing on mountains − with new research suggesting that the highest altitudes may be warming at a rate greater than expected.

Members of the Mountain Research Initiative collective report in Nature Climate Change that they found evidence that mountain peak regions were warming faster than the surrounding plateaus and lowlands.

The study − by Nick Pepin, leader of the Environmental Processes and Change Research Group at Portsmouth University in the UK, and colleagues from the US, Switzerland, Canada, Ecuador, Pakistan, China, Italy, Austria and Kazakhstan − comes with more than the usual set of health warnings.

The authors concede that the evidence is “extremely sparse”. But just as the Arctic region – the high latitudes of the northern hemisphere – is warming faster than anywhere else in the world, so the high altitude could also be at risk. The important thing is to find out.

No long-term data

There are few weather stations above 4,500 metres, and no long-term data for peaks higher than 5,000 metres anywhere in the world. The summit of Kilimanjaro, Africa’s highest mountain, has been monitored longest of all, but measurements have been recorded there on a systematic basis only for the last decade.

Other indications come from the Tibetan plateau, where temperatures recorded at 139 stations have risen steadily over the past 50 years, and the rate of change is accelerating.

“There is growing evidence that high mountain regions are warming faster than lower elevations,” Dr Pepin say. “Such warming can accelerate many other environmental changes, such as glacial melt and vegetation change, but scientists urgently need more and better data to confirm this.

“The social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought”

“If we are right, and mountains are warming more rapidly than other environments, the social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought.”

Kilimanjaro’s snow-covered peak in 1938. Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

Kilimanjaro’s snow-covered peak in 1938.
Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

There are two obvious causes for concern, the first being the simple problem of biodiversity. Plants and animals that occupy the highest elevations are at the optimum limits of their climatic tolerance, and if the climate gets warmer, they must move uphill to survive.

There is already evidence from alpine Switzerland that this is indeed happening. But those species already at the highest altitudes have nowhere else to go −  and so face extinction.

The second concern relates to an even more immediate impact. The highest mountain regions are glaciated, and this store of winter snow and ice becomes a source of spring and summer meltwater on which farmers, cities and even whole nations have grown to depend.

There is also good evidence that glaciers are in retreat, almost everywhere in the world. So the economic consequences could be considerable.

Endangered species

“This alone requires that close attention be paid to the issue,” the authors write. “In addition, mountains provide habitat for many of the world’s rare and endangered species, and the presence of many different ecosystems in close proximity enhances the ecological sensitivity of mountains to environmental change.”

In essence, the study incorporates a warning: more evidence is needed.

Raymond Bradley, who directs the Climate System Research Centre at the University of Massachusetts Amherst, spells it out: “We are calling for special efforts to be made to extend scientific observations upwards to the highest summits to capture what is happening across the world’s mountains.

“We also need a strong effort to find, collate and evaluate observational data that already exists wherever it is in the world. This requires international collaboration.” – Climate News Network

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Well drilling has deep impact on Great Plains’ health

Well drilling has deep impact on Great Plains' health

Loss of vegetation on North America’s vast rangelands as a result of a huge increase in oil and gas wells invokes memories of the 1930s Dust Bowl disaster.

LONDON, 27 April, 2015 − Oil wells and natural gas may have made individual Americans rich, but they have impoverished the great plains of North America, according to new research.

Fossil fuel prospectors have sunk 50,000 new wells a year since 2000 in three Canadian provinces and 11 US states, and have damaged the foundation of all economic growth: net primary production − otherwise known as biomass, or vegetation.

Brady Allred, assistant professor of rangeland ecology at the University of Montana’s College of Forestry and Conservation, and colleagues write in the journal Science that they combined years of high-resolution satellite data with information from industry and public records to track the impact of oil drilling on natural and crop growth.

They conclude that the vegetation lost or removed by the expansion of the oil and gas business between 2000 and 2012 added up to 10 million tonnes of dry vegetation, or 4.5 million tonnes of carbon that otherwise would have been removed from the atmosphere.

Loss of fodder

Put another way, this loss amounted to the equivalent of fodder for five million cattle for one month from the rangelands, and 120 million bushels of wheat from the croplands. This wheat equivalent, they point out, adds up to the equivalent of 13% of the wheat exported by the US in 2013.

Net primary production – the biomass that plants make from photosynthesis every day, all over the world – is the basis of all wealth and food security. It underwrites all other human and animal activity.

Human wealth depends ultimately on what grows in the ground, or what can be dug from the ground, and most of the latter – such as coal, oil and peat– was once stuff that grew in the ground.

The same net primary production is the basis of what economists sometimes call ecosystem services on which all civilisation depends: the natural replenishment of the water supply, the pollination of crops, the provision of natural nitrogen fertilisers, and the renewal of natural habitat for wild things.

“It took catastrophic disruption of livelihoods and economies [in the 1930s] to trigger policy reforms that addressed environmental and social risks of land-use change”

And what worries the conservation scientists is that this loss of net primary production is likely to be “long-lasting and potentially permanent, as recovery or reclamation of previously drilled land has not kept pace with accelerated drilling”.

“This is not surprising because current reclamation practices vary by land ownership and governing body, target only limited portions of the energy landscape, require substantial funding and implementation commitments, and are often not initiated until the end life of a well.”

They say that the land actually taken up by wells, roads and storage facilities just between 2000 and 2012 is about 3 million hectares. This is the land area equivalent to three Yellowstone National Parks.

The hydraulic fracturing, or “fracking”, used to extract oil and gas is between 8,000 cubic metres and 50,000 cubic metres per well, which means that the total quantity of water squirted into the ground at high pressure during the 12 years to 2012 could exceed 33,900 million cubic metres. At least half of this was used in areas already defined as “water-stressed”.

New wells

The researchers considered the drilling of new wells in Alberta, Manitoba and Saskatchewan in Canada, and in Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah and Wyoming in the US.

Although there is legislation, it is limited to lands subject to federal jurisdiction, and 90% of all drilling infrastructure is now on privately-owned land − at least, in the US.

A tanker drives past a flaring oil well in North Dakota. Image: Tim Evanson via Wikimedia Commons

A tanker drives past a flaring oil well in North Dakota.  Image: Tim Evanson via Wikimedia Commons

The study’s authors want decision-makers to confront the challenges of this kind of ecological disruption. There are lessons from history in all this, they warn.

“In the early 20th century, rapid agricultural expansion and widespread displacement of native vegetation reduced the resilience of the region to drought, ultimately contributing to the Dust Bowl of the 1930s,” they write.

“It took catastrophic disruption of livelihoods and economies to trigger policy reforms that addressed environmental and social risks of land-use change.” – Climate News Network

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History lessons highlight climate threat to birds

History lessons highlight climate threat to birds

Evidence from the Ice Ages helps show how vulnerable bird populations are to change driven by human-induced global warming.

LONDON, 25 April, 2015 − Climate change can seriously alter the numbers and the prospects for survival of the planet’s living things, according to researchers in Sweden and China.

The scientists’ findings are the result of taking a long, cool look at the big picture – rather than the still-sketchy evidence from climate change now – of what happened to bird populations during the Ice Ages.

Krystyna Nadachowska-Brzyska and Hans Ellegren, of the Evolutionary Biology Centre at Uppsala University, and collaborators at the Beijing Institute of Genomics used a sophisticated new technique to calculate the rise and fall of population sizes of 38 species of bird during the last several million years − a period punctuated by the advance of vast sheets of ice and shorter warm interglacial periods.

Natural change

The results answer questions about how species fared during periods of natural change, in an era when human numbers were tiny and human technology insignificant.

But they also highlight the vulnerability of already-endangered bird populations during a period of change driven by global warming as a consequence of greenhouse gas emissions into the planet’s atmosphere from the widespread use of fossil fuels.

The researchers exploited techniques made possible only in the last decade or so to recreate the past.

They compared genomic mutations among unrelated individuals in each species, and employed a new mathematical technique that goes by the name of “pairwise sequentially Markovian coalescent”, or PSMC, to tease out the history encoded in those comparisons.

“Climate events significantly affect the effective breeding sizes of bird populations”

The reasoning goes like this: mutations in DNA occur at a more or less predictable rate through the generations of a species, so DNA can be considered both as an indicator of relationships and as a kind of clock.

Using such a clock, based on DNA inherited only through the maternal line, scientists long ago calculated a potential date for the origins of Homo sapiens.

In 2011, a team of scientists reasoned that the same clock, subjected to some mathematical interrogation, might answer questions about how many individuals might have existed in a population at a particular time.

Their first result was to confirm from the variation – or lack of variation – in the genome samples that some distant catastrophe caused a sharp drop in human population numbers 60,000 years ago or more, after which human numbers expanded again.

Now the same techniques have been applied to genomic evidence from barn owls, budgerigars, bald eagles, Dalmatian pelicans, domestic pigeons and Pekin ducks, as well as less familiar creatures such as the rhinoceros hornbill of south-east Asia, and the kea, a ground-dwelling alpine parrot from the South Island of New Zealand.

“The majority of all species exhibit cyclical swings in numbers, and these swings often coincide with the periods of ice ages,” Dr Ellegren says. “The last ice age (110,000-12,000 years ago) had a particularly heavy impact on birds. Many species suffered their most dramatic falls in numbers then.”

What the scientists were looking for was something called “historically effective population size” in their choice of species − broadly, the number of survivors that could interbreed and rear the next generation.

In the case of, for example, the downy woodpecker of North America, this number was at a low point of 150,000 two million years ago, then rose to 1.2 million before falling, around 100,000 years ago, to about 200,000.

Severe declines

They found severe declines in 22 of the 38 species over a period that coincided with the last ice age. Two species of eagle and the common ostrich saw their numbers reduced from tens of thousands to mere thousands. But even much more numerous species, such as pigeon and budgerigar, experienced significant change.

Scientists have already begun to measure change in the natural world in response to average temperature rises by shifts either in timing or latitude, or even altitude.

The Uppsala research offers a kind of baseline of historical change, and could help conservation bodies now concerned with saving species already considered at risk of extinction because of habitat destruction, hunting and human-induced climate change.

“The results from our study document that such climate events significantly affect the effective breeding sizes of bird populations,” the authors conclude. – Climate News Network

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Familiar fish find northern seas too warm for comfort

Familiar fish find northern seas too warm for comfort

Fish accustomed to shallow northern waters will search in vain for cooler depths as climate change warms the seas where they thrive.

LONDON, 18 April, 2015 – Some of Northern Europe’s favourite suppers may be about to swim off the menu altogether. Global warming could change the future catch, according to new research.

British scientists report in the journal Nature Climate Change that popular species such as haddock, lemon sole and plaice could become less common as the climate changes and the North Sea warms.

The North Sea is relatively shallow – during the height of the Ice Age, much of the sea bed was dry land – which means that fish that would otherwise find deeper waters to keep cool have nowhere to go.

The North Atlantic is warming fast. The mean annual North Sea surface temperatures have increased by 1.3°C in the past 30 years. This is four times faster than the global average. But fish evolved to make a living in the temperatures that suit them best, and the evidence is that the North Sea is increasingly host to species that were once characteristic of the Mediterranean.

Changing abundance

Fishing is big business: landings in 2007 in the region reached $1.2 billion, and accordingly the ecology of the North Sea has been intensively monitored. Cold-adapted landings have halved in the last 30 years, but landings of warm-adapted species have increased 2.5 times. With a baseline of very detailed data from the past, the researchers were able to use computer models to build up a picture of things to come in northern waters.

And the result is this: the demersal or bottom-feeding fish that were the basis of fish-and-chip suppers from Cornwall in the UK to northern Norway are likely to dwindle over the next 50 years. Many of them cannot move north to get away from the heat, because there is no suitable habitat, and they can’t go deeper, because there isn’t any depth. So the abundance of species will change with time.

“Our study suggests that we will see proportionately less of some of the species we eat most of as they struggle to cope with warming conditions in the North Sea,” said Louise Rutterford of Exeter University, the first author.

Squeezed out

“We provide new insight into how important local depths and associated habitats are to these commercial species. It’s something that is not always captured in existing models that predict future fish distributions.”

Other studies have found that fish in many regions are changing to new latitudes as climates change in response to greenhouse gas emissions from fossil fuel combustion. The same man-made global warming has brought a greater number of sardines, for instance, to northern waters, and in the US fishermen have had to sail ever further north to pursue the black bass. There has even been a warning that the retreat of the Arctic ice means that Atlantic halibut could actually migrate into the North Pacific.

So the latest message is confirmation of an increasingly familiar finding. “We will see a real changing of the guard in the next few decades,” said Steve Simpson, a marine biologist at Exeter, and another of the authors.

“Our models predict cold water species will be squeezed out with warmer water fish likely to take their place. For sustainable UK fisheries, we need to move from haddock and chips and look to southern Europe for our gastronomic inspiration.” – Climate News Network

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Polar bears weakened by pollution as well as warmth

Polar bears weakened by pollution as well as warmth

Climate change causing habitat loss and reduced food is the main problem for polar bears, but plastic waste and other pollutants are growing risks.

LONDON, 17 April, 2015 − Greenland’s polar bears have a thyroid problem. Their endocrine systems, too, are being disrupted. In both cases the culprit agency is environmental pollution by a range of long-lived industrial chemicals and pesticides.

Kristin Møller Gabrielsen of the Norwegian University of Science and Technology in Trondheim and colleagues report in the journal Environmental Research that they examined the liver, muscle and kidney tissues taken from seven polar bears killed by Inuit hunters in East Greenland in 2011 and analysed the effect of more than 50 contaminants in plasma samples from Ursus maritimus, to see what effect organohalogen compounds could have on the bears’ thyroid systems.

All mammals have thyroid systems, and these are physiologically essential for growth, development, reproduction, stress response, tissue repair, metabolism and thermoregulation (an animal’s ability to keep its body temperature within limits): disruption at any stage of life can be damaging, but thyroid regulation is vital in the earlier stages of life.

But the researchers found high concentrations of plastic pollution and pesticide contamination in the creatures’ tissues, many of which could affect the hormonal systems.

Retreating ice

Polar bears face an uncertain future: the Arctic’s most iconic predator depends on sea ice for access to the most nourishing prey – seals − but thanks to global warming driven by greenhouse gases discharged by humankind since the start of the Industrial Revolution, the ice is in retreat. The bears can and do forage on land for small prey, eggs, berries and so on, but new research suggests that this is unlikely to help them much.

“The health of the Arctic polar bear is being attacked from all fronts, but among many other factors is the exposure to environmental contaminants,” said Maria Jesus Obregon, of the Biomedical Research Institute in Madrid, one of the authors.

“A wide variety of organochlorine compounds and pesticides have an effect on the thyroid hormones in plasma, tissues and deiodinase enzymes, which are in charge of stabilising the thyroid hormones in tissues.”

The biggest problem that confronts Ursus maritimus is still climate change, loss of habitat and a more precarious food supply. But as a marine mammal, the bear is exposed to a huge range of pollutants delivered by modern industry, transport and commerce.

Conservation guidelines

Researchers in February calculated that in 2010, around eight million tons of plastic waste
ended up in the world’s oceans.

A second team of researchers has framed guidelines for the conservation of the polar bear, and proposed 15 measures that could determine the factors important in saving the creature from ultimate extinction.

They report in the journal Science of the Total Environment that they questioned 13 specialists from four nations to propose ways of measuring polar bear health. Not surprisingly, climate change topped the list of threats, but the list also included nutritional stress, chronic physiological stress, diseases and parasites, and increasing exposure to competitors. Exposure to contaminants was the third largest threat.

“We still don’t know to what extent environmental changes will affect polar bear health and therefore its conservation,” say the authors. − Climate News Network

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Too much nitrogen reduces Alpine plant diversity

Too much nitrogen reduces Alpine plant diversity

Climate change caused by one of the less abundant greenhouse gases is playing havoc with plant life in Switzerland, posing problems for other forms of life and increasing the risk of erosion.

LONDON, 15 April, 2015 − Carbon dioxide isn’t the only greenhouse gas to change the world. Swiss scientists have just confirmed that nitrous oxide and other forms of atmospheric nitrogen deposition – from agriculture, from factory chimneys and motor exhausts and so on – is altering the grasses and wildflowers of the Alps and the valleys.

Plants cannot live without nitrogen: for most of evolutionary history, it has been available only in limited amounts. With the Industrial Revolution, that began to change. Tobias Roth of the University of Basel and colleagues report in the Royal Society journal Open Science  that the historic rise in the availability of nitrogen has reduced plant diversity everywhere in Switzerland.

The finding is not – of itself – new. Researchers tested the hypothesis that increasing levels of nitrogen presented a threat to “hotspots” of global biodiversity almost a decade ago. But in science, one general study is never enough.

More nitrogen

So Dr Roth and his colleagues did something much more detailed and comprehensive. They used six different measures of plant diversity to test what was happening on 381 study plots at a variety of altitudes and in different kinds of ecosystems across just one country. However the scientists measured plant diversity, it had been reduced.

That human-triggered changes to the atmosphere have affected Switzerland is not in much doubt: one research team recently established that alpine glaciers were in retreat in response to atmospheric pollution, and Dr Roth – now with the Swiss company Hintermann and Weber AG – last year demonstrated that birds, flowers and butterflies in the country were all heading uphill in response to global warming.

The latest research began with a baseline from earlier centuries: data taken from herbarium samples confirmed that available nitrogen had once been much more limited. The scientists then randomly selected 428 study plots – each a kilometre square – as their study samples.

Some had to be rejected, because they were entirely water, or in mountainous regions too rugged and dangerous for field research. But that left 381 sample plots, in the Alps and the Jura mountains, between the altitudes of 260 and 3,200 meters (850 and 10,500 feet).

Bad news

The researchers used qualified botanists who had received special training to conduct the surveys, and asked them to conduct, as closely as they could, a diagonal transect examination across each plot, if possible once in spring and again in summer, and to record all vascular plants. Altogether, the surveys delivered 93,621 observations of 1,768 plant species.

The scientists found that biodiversity had declined by 19% according to one measure and by 11% in another test. In general, the higher the nitrogen available, the lower the diversity.

This is bad news for ecosystems as a whole: diversity means stability. Extra sources of nitrogen fertility benefit some highly competitive groups of plants, at the expense of others.

“High plant diversity is important to us humans for many reasons,” said Valentin Amrhein, another of the authors. “For example, in the mountains a large number of plant species with different root depths will stabilise the soil more effectively and prevent erosion.” − Climate News Network

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Woodlands revival adds new piece to carbon cycle puzzle

Woodlands revival adds new piece to carbon cycle puzzle

Growing number of trees on the world’s savanna grasslands helps offset carbon storage concerns caused by depletion of the great rainforests.

LONDON, 9 April, 2015 − Despite continuing concern about the fate of iconic rainforests, new research shows that the world’s forests have stored away an extra 4 billion tonnes of carbon in the last dozen years and the total amount of woodland has increased worldwide since 2003.

The encouraging news comes from Australian scientists, who report in Nature Climate Change that they used a new technique to analyse 20 years of satellite data, to estimate the overall pattern of growth in global vegetation.

The fate of the forests could hardly be more important. The world’s greenery is part of the natural atmospheric cycle, and the notorious greenhouse effect – the steady rise in carbon dioxide levels in the Earth’s atmosphere since the start of the Industrial Revolution and the use of fossil fuels to power economic growth – is in part also a response to land-use change and forest loss. Growth requires atmospheric carbon dioxide, and burning and land clearance releases it.

Biggest headache

So the study by remote sensing scientist Yi Liu, of the Climate Change Research Centre at the University of New South Wales, and colleagues becomes an important contribution to solving the climate scientist’s biggest headache: making sense of the carbon budget.

Accurate climate models depend on accurate assessment of the carbon cycle, and the forests play a critical role. Timber in the forests is essentially carbon in the bank.

And, for once, the news is encouraging. The great rainforests of the Congo and the Amazon may not be doing so well, but grasslands in other parts of the world have become increasingly more wooded, and there has been a massive expansion of forested land in China.

“The increase in vegetation primarily came from a lucky combination of environmental and economic factors, and massive tree-planting projects in China,” Dr Yi Liu says.

“Vegetation increased on the savannas of Australia, Africa and South America as a result of increasing rainfall, while in Russia and former Soviet republics we have seen the re-growth of forests on abandoned farmland. China was the only country to intentionally increase its vegetation with tree-planting projects.”

The Australian scientists are not the only researchers using instruments in high orbit to identify the green shoots of recovery.

“A lot rides on human decisions to slow
climate change. The clock is ticking
for the future of these forests”

Dmitry Shchepashchenko, a researcher at the International Institute for Applied Systems Analysis in Austria, and colleagues report in the journal Remote Sensing of Environment that a cocktail of remote sensing data, UN agency statistics and “crowdsourcing” – help from citizen scientists – has provided new high resolution maps of global forest cover.

This will serve as a basis for other studies, and for economic planning and policy-making. The maps are available on the Geo-Wiki website.

But the overall picture of a greener world remains uncertain. On the same day, scientists backed by the Carnegie Institution in Washington reported in Nature Geoscience that drought damage has already led to widespread forest death, and the toll could be much greater by the 2050s.

They based their study on the condition of the trembling aspen forests of the American southwest during the drought of 2000-2003.

Once again, their work is aimed at improving climate models and calculations of the response of forests to climate change, and could throw new light on the processes at work in forests subjected to water stress.

Drought damage

That is because the arboreal vascular system that transports water from the roots to the leaves is itself damaged by drought. But at what level would drought impose permanent damage on a tree’s physiology?

The Carnegie scientists were able to establish a drought threshold for the trembling aspen (Populus tremuloides), and the drought at the beginning of the century is known to have killed 17% of the species in Colorado.

The research is fundamental: just one study of one species in one region that provides a starting point for further studies, and thus for surer measures of vegetation response to climate change, and ultimately to a better understanding of the carbon cycle.

“Finding the thresholds in plant physiology, after which climate stress causes tree mortality, will allow us to resolve uncertainty over the fate of forest ecosystems in a changing climate,” says the study leader, William Anderegg, a researcher at Princeton Environmental Institute in the US.

“But, most importantly, a lot rides on human decisions to slow climate change. The clock is ticking for the future of these forests.” – Climate News Network

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Climate poses new threat to survival of Arabian oryx

Climate poses new threat to survival of Arabian oryx

Global warming is the suspected cause of the series of dry years in Arabia that have brought starvation to a desert species saved from extinction.

LONDON, 7 April, 2015 − One of conservation’s triumphs – the reintroduction of the oryx to the deserts of Arabia – could be at risk because of climate change, according to a new book.

The animal already beautifully adapted by thousands of years of evolution to an arid environment met a problem on its return: even deserts have droughts.

The Arabian oryx had been hunted almost to extinction before a handful were captured in 1962 and flown to Phoenix, Arizona, as the nucleus of a captive breeding programme.

By 1972, the last wild oryx had been captured or killed in Oman, but the bloodline survived in captivity.

The first reintroductions to the wild began in 1982, and numbers began to increase. There were incursions by poachers, but there were more releases.

However, there have been so many dry years over the last two decades − according to Malcolm Smith, once chief scientist for the Countryside Commission in Wales, in his new book, Back from the Brink − that many of the newly-wild oryx have not been able to find sufficient grazing.

Closely monitored

The animal is one of the most closely monitored in the world. Of all recorded deaths, 19% have occurred in fights between males, 13% have been due to poaching, and 65% have been due to starvation.

The succession of particularly dry years in the region might be due to global warming as a consequence of human combustion of fossil fuels.

Since climate simulations seem to predict that, in general, moist regions will get more rain and dry regions will experience ever drier regimes as greenhouse gas levels build up in the atmosphere, things don’t look good for the oryx − although captive populations for the time being remain secure.

Other recently-rescued species may face even leaner times − once again, because of climate change.

Spanish and Portuguese authorities have established safe territories for the Iberian lynx and, by 2013, more than 300 lived wild in Spain, while 150 lynx paced the enclosures in the breeding centres awaiting reintroduction.

But the wild rabbit makes up 90% of the lynx’s diet, and rabbit numbers are limited by hunting and by outbreaks of myxomatosis and rabbit haemorrhagic disease.

There have been fears too, that southern Spain and Portugal may become too hot and dry to sustain the prey, let alone the predator.

Such threats to biodiversity, and to individual animals, are not new. Climate change has in various ways reportedly threatened Arctic marine mammalscreatures of the Borneo forests,  and chimpanzees in isolated woodland in West Africa.

Whole ecosystems that evolved in geographical climate zones may be doomed to sudden and rapid change.

But Malcolm Smith’s book concerns itself only with the choicest last-minute success stories of conservation bodies: with those creatures that were all but gone when the conservationists stepped in.

They were hunted, their habitats had been destroyed, and their ecosystems were always precarious. But climate change was, at the time of rescue, the least of their problems.

Large Blue butterfly (Maculinea arion). Image: PJC&Co via Wikimedia Commons

Large Blue butterfly (Maculinea arion).
Image: PJC&Co via Wikimedia Commons

One instance he explores shows just how intricate the living arrangements of charismatic species can be, and illustrates the finely-balanced play of climate and ecological stability in preserving a species.

The Large Blue butterfly (Maculinea arion) exists in respectable numbers worldwide, but became all but extinct in the UK − with changes in farming practices and land use the suspected causes.

Peculiar lifestyle

Until 1972, nobody quite understood the peculiar lifestyle of the Large Blue. It lays its eggs on the flower bud of the wild herb, thyme. A larva hatches and, after an initial vegetarian diet, falls off the plant. Thereafter, its life depends on just one species of red ant, Myrmica sabuleti.

The Large Blue grub secretes a fluid that somehow suggests that of a red ant queen grub, so the ants take it home and nurse it. The Large Blue caterpillar turns carnivore and, for 10 months, feeds on red ant larvae.

In pupate form, it makes queen ant noises and the ants continue to protect it. It hatches, gets out to the open − still protected by the ants − and flies off. It then has about a week in which to find a thyme flower bud, mate, and lay its eggs.

But the complexities multiply. The thyme flower bud that bears the eggs must be within metres of the right kind of red ant nest, or the larva perishes.

Dependent on temperature

The grass above the ant nest must be closely grazed because the ants’ survival is dependent on temperature, and if the grass grows even a centimetre ground is shaded, the nest temperature drops by 2°C to 3°C, and the ant colony is at risk − along with any parasitic caterpillars in the nest.

So the thyme has to flower at the right time, very near a red ant nest, the herbage has to be closely cropped, and the temperatures have to stay near the optimum.

If anything goes wrong, there are no surviving Large Blue larvae to pupate. If things go well, and too many Large Blue grubs are taken into a colony, the ant larvae are all consumed, and both ants and butterflies perish.

And then there’s the climate question − one that affects almost all insects.

“Overall, butterfly populations have moved northward by about 75km in the last 20 years as overall temperatures have risen,” Smith writes. “They are likely to move yet further.” – Climate News Network

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Climate-driven loss of habitat endangers marine mammals

Climate-driven loss of habitat endangers marine mammals

Global survey of threatened Arctic species warns that conservation won’t work without regulation of greenhouse gas emissions to halt climate change.

LONDON, 2 April, 2015 − Three kinds of whale, six varieties of seal, the walrus and the polar bear all have things in common: they are marine mammals, they depend on the Arctic for survival as species, they are vulnerable, and biologists know surprisingly little about them.

And since the Arctic is warming twice as fast as the rest of the planet, their future could become even more threatened as climate change increases habitat loss.

The stress, so far, is on the word “could”, as the first challenge is to establish the facts.

A global study team led by Kristin Laidre, principal scientist at the University of Washington Polar Science Centre in Seattle, reports in the journal Conservation Biology that marine mammals are “disproportionately threatened and data poor compared with their terrestrial counterparts”.

The narwhal, beluga and bowhead whales, the ringed, bearded, spotted, ribbon, harp and hooded seals, the walrus, and the polar bear are “particularly vulnerable due to their dependence on sea ice”.

Important predators

All these animals make their living on the ice and in waters north of the Arctic Circle, and all are important predators. They are also important to indigenous and settler peoples in the frozen North as many can be legally harvested, and others are iconic tourist attractions. Either way, they help communities survive.

“These species are not only icons of climate change, they are also indicators of ecosystem health, and key resources for humans,” Dr Laidre says. “Accurate scientific data – currently lacking for many species – will be key to making informed and efficient decisions about conservation challenges and trade-offs in the 21st century.”

So the researchers set out on what they believe is the first comprehensive global review of what is known about the populations of these animals, and about the way their local habitats may be changing.

“They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life.”

The study divided the Arctic into 12 regions and began to look at population numbers and trends, and the local pattern of seasonal change in the ice.

They identified 78 distinct populations of the 11 species, and began to assemble estimates of numbers. These range from millions for the ringed seals to a few hundred for the beluga whales of Ungava Bay in the Canadian Arctic.

In many cases, researchers had too little information even to make a guess about whether local populations of any species were stable, declining or increasing. In their table of the trends of the 11 species in the 78 populations, the word “unknown” occurs more than 60 times.

They also charted profound reductions in ice cover. The sea ice naturally advances each winter, and retreats each spring, but because of global warming driven by human emissions of greenhouse gases released by fossil fuel combustion, the pattern of advance and retreat has changed dramatically. By 2040, according to some projections, the Arctic could be more or less ice-free each summer.

Extended summer

But change is visible now. In most regions, the scientists found that the summer period was extended by between five and 10 weeks. In Russia’s Barents Sea, the summer ice period is now 20 weeks longer – five months – than it was 30 years ago.

This presents a threat to the polar bear, and to the seals on which they feed. “These animals require sea ice,” Dr Laidre says. “They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life. It is very clear those species are going to feel the effects the hardest.”

On the other hand, the whale species might benefit – at least for a while – from reduced ice cover. Open water could offer a wider feeding range and greater marine productivity, and therefore more food.

The scientists provide a set of general recommendations for biologists, local authorities, government agencies and international organisations concerned with conservation of Arctic marine mammals. They also have a message for the entire planet.

As Dr Laidre says: “We may introduce conservation measures or protected species legislation, but none of those things can really address the primary driver of Arctic climate change and habitat loss for these species. The only thing that can do that is regulation of greenhouse gases.” – Climate News Network

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