Western US and Southeast Asia face rising dust risk

October 26th, 2020, by Tim Radford

The 1930s Midwest Dust Bowl: An abandoned farm in Texas. 

Image: By Dorothea Lange, CC0, via Wikimedia Commons

It obscures the skies and darkens the snows. Wind-borne dust risk is increasingly ominous in a warming world.

LONDON, 26 October, 2020 − Half a planet apart, one low-lying and the other on the roof of the world, two huge regions confront an increasing dust risk − a menace to jobs, to food and to lives.

The Great Plains of North America are getting dustier every year because more soil is now being exposed to erosion. And high in the Himalayas on the continent of Asia, the peaks too are becoming dustier, in ways that threaten to increase the melting of high-altitude snows.

Both findings are in essence bad news. In the western US, higher levels of wind erosion as a consequence of changing farm practices combined with ever-greater probabilities of drought mean ever-higher probabilities of a return of the Dust Bowl that devastated the US Midwest 90 years ago.

And 700 million people in Southeast Asia, China and India depend on the slow melting of the Himalayan glaciers to irrigate their crops in the hot dry season: earlier melting threatens not just livelihoods but lives.

Taken for farming

In the 1930s, the Great Plains region was hit by drought that extended from Canada to Mexico. By then, vast tracts of prairie had been converted from wild grassland to ploughed field.

“The result was massive dust storms we associate with the Dust Bowl. These dust storms removed nutrients from the soil, making it difficult for crops to grow and more likely for wind erosion to occur,” said Andrew Lambert of the University of Utah.

He and colleagues from Colorado report in the journal Geophysical Research Letters that they measured atmospheric dust levels by studying evidence from both space and from the ground, and collected data from 1988 to 2018.

They found that atmospheric dust over the Great Plains was increasing at 5% a year. That would mean a doubling in just two decades.

“The massive dust storms we associate with the Dust Bowl removed nutrients from the soil, making it difficult for crops to grow and more likely for wind erosion to occur”

They also found that levels of dust matched the planting and harvest months of soybean in the north, and corn in the southern states. How the land was farmed could be connected directly to the haze in the air.

Dust plays a powerful role in planetary management: researchers established years ago that the rich biodiversity of the Amazon rainforest was nourished and supplemented almost annually by deposits of fertile dust blown across the Atlantic from the African Sahara. And dust falling into the ocean on the journey also helped nourish marine life far below the surface of the Atlantic.

Now it seems that wind-blown dust from two continents also settles on the biggest and highest tracts of the Himalayas, to darken the snow, change its reflectivity and absorb the sun’s warmth.

Scientists from the US Pacific Northwest National Laboratory report in Nature Climate Change that they used detailed satellite imagery of the Himalayas to measure aerosols, elevation and snow surfaces to identify dust and other pollutants.

Constant release

They found that, at up to 4500 metres altitude, black carbon or soot played an important role in influencing the melt timetable of the high snows. Above that altitude, dust was the most important factor: dust from the Thar desert in India, from Saudi Arabia and even from the African Sahara.

Although this was part of a natural cycle, humankind may be accelerating the traffic and adding to the dust risk: ever-higher planetary temperatures have begun to affect atmospheric circulation. And as humans turn natural ecosystems into farmland, they release even more dust.

“The snow in the western Himalayas is receding rapidly. We need to understand why this is happening and we need to understand the implications,” said Chandan Sarangi, then at Pacific Northwest but now at the Madras Institute of Technology in Chennai, and one of the authors.

“We’ve shown that dust can be a big contributor to the accelerated snowmelt. Hundreds of millions of people in the region rely on snow for their drinking water − we need to consider factors like dust seriously to understand what’s happening.” − Climate News Network

Poor air inflicts billions of premature deaths in Asia

October 22nd, 2020, by Nivedita Khandekar

Traffic jam in Beijing: But China has made big strides towards air quality improvement. 

Image: By public domain, via Wikipedia Commons

Air pollution by tiny particles is among the world’s worst health risks. In South Asia, poor air is as bad as it gets.

NEW DELHI, 22 October, 2020 − Poor air costs lives, but finding out just how many of them will come as a shock to many residents of South Asia’s big cities.

In India’s capital, New Delhi, just going outside and breathing the air can shorten your life by more than nine years, according to a new report into the region’s air quality that measures the effects of pollution on life expectancy.

For millions of people across across north-west India, Pakistan and Bangladesh, it will be bad news − despite the Covid crisis − because of the current surge in air pollution in the region.

But none of the people of four countries, India, Pakistan, Bangladesh and Nepal, will be happy with the prediction that their lives will be shortened unless their governments take air pollution seriously.

New Delhi is the worst single example in the four, but few of their citizens − a quarter of the world’s population − will escape.

Bangladesh worst hit

Averaged across the whole population, the people of Bangladesh suffer most from air pollution in any country, with their average life span cut short by 6.2 years.

An air quality index (AQI) provides daily air quality assessments, but not the actual health risk. An air quality life index (AQLI) goes further: it converts particulate air pollution into perhaps the most important air pollution metric that exists: its impact on life expectancy.

The report is the work of the Energy Policy Institute at the University of Chicago (EPIC), which has recently updated its AQLI, based on research by its director Michael Greenstone that quantified the causal relationship between human exposure to air pollution and reduced life expectancy.

While the report makes grim reading for nations south of the Himalayas, it does offer some hope, saying that the people of China can see marked improvements since their government began clamping down on polluting industries in 2013.

The report uses two measures to calculate lower expectations of life expectancy: the more stringent World Heath Organisation guidelines (WHO) and the limits imposed by the governments concerned.

“The threat of coronavirus is grave and deserves every bit of the attention it is receiving [but] embracing the seriousness of air pollution with a similar vigour would allow billions of people around the world to lead longer and healthier lives”

It says air pollution shortens Indian average life expectancy by 5.2 years, relative to what it would be if the WHO guidelines were met, but by 2.3 years relative to the rate if pollution were reduced to meet the country’s own national standard.

Some areas of India fare much worse than the average, with air pollution shortening lives by 9.4 years in Delhi and 8.6 years in the northern state of Uttar Pradesh, the report’s India fact sheet 2020 says.

Similarly, the Pakistan sheet says the average Pakistani’s life expectancy has been shortened by 2.7 years, while air pollution cuts lives by more than 4 years in the most polluted areas.

Naming Bangladesh as the world’s most polluted country, EPIC’s report says air pollution shortens the average citizen’s life expectancy by 6.2 years, compared to what it would be if the WHO guidelines were met.

Again, some areas suffer far more, with lives cut by about 7 years in the most polluted district. In every one of the country’s 64 districts, particulate pollution levels are at least four times the WHO guidelines.

Possible underestimate

Surprisingly Nepal, which unlike its southern neighbours is not normally associated with air pollution, also had serious problems with its crowded and polluted cities. As a result, life expectancy there is cut by 4.7 years across the whole population.

“Though the threat of coronavirus is grave and deserves every bit of the attention it is receiving − perhaps more in some places − embracing the seriousness of air pollution with a similar vigour would allow billions of people around the world to lead longer and healthier lives,” says Professor Greenstone.

The science of air pollution, and the impact of poor air on the human body, is evolving rapidly, and some Asian scientists have expressed reservations about the accuracy of some of the calculations. However, none of them disputes the fact that millions are dying early because of the pollution.

The report concentrates on the effect of the smaller particulates that are known to do the most damage to lungs, and to enter the bloodstream, and it may in fact be underestimating the overall effects of poor air quality. − Climate News Network

* * * * * *

Nivedita Khandekar is an independent journalist based in New Delhi, covering development and the environment: nivedita_him@rediffmail.com and on twitter at @nivedita_Him

More avoidable pandemics await a heedless world

November 11th, 2020, by Tim Radford

On sale in China: Bushmeat, an open road to microbial transfer between species. 

Image: By Simon Law, via Wikimedia Commons

There will be more avoidable pandemics, more devastating and lethal, as humans intrude further upon the planet’s forests.

LONDON, 11 November, 2020 − Once again, naturalists have warned that the invasion of wilderness can seriously damage human health: avoidable pandemics − Covid-19 is an instance of a disease transferred from wild mammals to humans − threaten to arrive more often, spread more rapidly, do more damage to the global economy, and kill more people.

That’s because the odds on even more fearful infections remain very high: the world’s wild mammals could between them be hosts to 1.7 million viruses that have yet to be identified and named. If only a third of them them could infect humans, that’s 540,000 new diseases waiting to happen.

The number could be higher: perhaps 850,000 potential infections lie so far undisturbed, waiting to happen.

A new report by a team of 22 global experts warns that Covid-19 is at least the sixth global health pandemic since the Great Influenza Epidemic of 1918: all had their origins in microbes carried by animals, and all were awakened and spread by human interaction with the wilderness.

By July 2020, the coronavirus linked to a market in wild animals in Wuhan in China had spread around the planet at a cost of between US$8 trillion and $16tn. The world has already seen the Ebola virus devastating West African communities, the HIV/Aids epidemic, Zika, and many others claiming lives in the last century.

Wilderness no more

The arrival of new zoonotic diseases − infections caught from other creatures − has been counted at roughly two a year since 1918. The number could increase to as many as five a year. And most of them will be linked to increasing human impact upon what had once been largely undisturbed wilderness.

“There is no great mystery about the cause of the Covid-19 pandemic − or of any modern pandemic”, said Peter Daszak, president of EcoHealth Alliance and chair of a workshop of the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES for short) that assembled the research.

“The same human activities that drive climate change and biodiversity loss also drive pandemic risk through their impacts on our environment. Changes in the way we use land; the expansion and intensification of agriculture; and unsustainable trade, production and consumption disrupt nature and increase contact between wildlife, livestock, pathogens and people. This is the path to pandemics.”

All living things are host to viruses and other microbes: in most cases host and parasite adapt to live peaceably with each other. The danger comes when a microbe transfers to a new host that is entirely unprepared for the invader.

“We still rely on attempts to contain and control diseases after they emerge. We can escape the era of pandemics, but this requires a greater focus on prevention”

What became known as the human immuno-deficiency virus HIV-1 is believed to have emerged first in West or Central Africa from the remains of chimpanzees hunted and sold for bushmeat. It spread around the planet within a decade, to claim millions of lives as the disease AIDS. Ebola infects both primates and humans: in an outbreak among humans, it has been known to kill 90% of all infected people.

Researchers have consistently linked epidemic and pandemic outbreaks to climate change, to the destruction and degradation of the wilderness, and to the traffic in wild creatures as objects of value or commerce.

And all are consequences ultimately of exponential growth in human numbers in the last century, a growth that puts ever greater pressure on what had once been largely undisturbed tropical forest, grassland and wetland.

Around a quarter of all wild terrestrial vertebrate species are traded globally. International, legal wildlife trade has increased fivefold in revenue in the last 14 years. It is now worth an estimated $107bn.

The illegal traffic in wildlife could be worth anywhere between $7bn and $23bn annually. The US imports around 10 to 20 million wild animals a year. In China in 2016, what is now called wildlife farming employed 14 million people and generated $77bn in revenue.

Negligible cost

Researchers have already argued that intrusion into what should be protected ecosystems that are home to the shrinking pool of wild birds, mammals, reptiles and amphibians − a million species could be nearing global extinction − not only threatens the wellbeing of the planet; it also generates an increasing health hazard.

The latest study lists a range of policy options to reduce the risk of assault by new plagues. These rest upon greater awareness of, and respect for, the natural capital of the wilderness. Conservation of this kind costs money, but at least 100 times less than the toll of successive pandemics likely without a change in human attitudes.

“We have increasing ability to prevent pandemics, but the way we are tackling them right now largely ignores that ability,” Dr Daszak said. “Our approach has effectively stagnated − we still rely on attempts to contain and control diseases after they emerge, through vaccines and therapeutics.

“We can escape the era of pandemics, but this requires a greater focus on prevention in addition to reaction.” − Climate News Network

 Carbon speeds crop growth but often for little gain

November 10th, 2020, by Paul Brown

The world depends on rice, one crop less likely to thrive on increased carbon.

 Image: By Wibi Wibisono on Unsplash

More carbon dioxide speeds up crop growth with some key food harvests, but extra heat can hit the yield.

LONDON, 10 November, 2020 − Thirty years of experiments in testing crop growth, and notably the effects of increased atmospheric carbon dioxide (CO2) on some human staples like rice, wheat and soya, have found that − given perfect growing conditions − they would increase yields by 18%.

But sadly, in “real world” conditions, any gains from carbon fertilisation are lost − because of the stress caused to crops by the 2°C temperature rise that the gas causes in the atmosphere. Even worse, the fact that crops grow faster does not mean that their nutritional value is greater – many showed lower mineral nutrients and protein content.

The work, 30 years of “free air carbon dioxide enrichment” (FACE), carried out by 14 long-term research facilities in five continents, is a blow to the hope that in a world with more atmospheric CO2 more people could be fed with less land under cultivation. Earlier results had held out the hope that this “fertiliser effect” would feed more people.

While commercial growers of plants like tomatoes, peppers and cucumbers have used increased CO2 to boost production in controlled conditions in greenhouses, it does not work so well in open fields where temperature and moisture content are affected by climate change.

“When you have other stresses, you don’t always get a benefit of elevated CO2. The last 15 years have taught us to account more for the complex interactions from other factors”

Some crops do get a boost from more carbon in the atmosphere because it makes photosynthesis more efficient, but this is only if nutrients and water are available at optimum levels. This group includes soybean, cassava and rice, all vital in feeding some of the hungriest people in the world.

The author of the study, Stephen Long from the University of Illinois,  said that while it seemed reasonable to assume “a bounty as CO2 rises” this was not the case, because “CO2 is the primary cause of change in the global climate system. The anticipated 2°C rise in temperature, caused primarily by this increase in CO2, could halve yields of some of our major crops, wiping out any gain from CO2.”

His co-author Lisa Ainsworth, a research plant physiologist with the US Department of Agriculture, said: “It’s quite shocking to go back and look at just how much CO2 concentrations have increased over the lifetime of these experiments.

“We are reaching the concentrations of some of the first CO2 treatments 30 years back. The idea that we can check the results of some of the first FACE experiments in the current atmosphere is disconcerting.

Need for nitrogen

“Lots of people have presumed that rising CO2 is largely a good thing for crops, assuming more CO2 will make the world’s forests greener and increase crop yields,” Ainsworth said.

“The more recent studies challenge that assumption a bit. We’re finding that when you have other stresses, you don’t always get a benefit of elevated CO2. The last 15 years have taught us to account more for the complex interactions from other factors like drought, temperature, nutrients and pests.”

The poor quality of some of the grain, with less mineral and protein content, is also a blow to add to the crop growth doubts. The potential increased yield is also much smaller under conditions where there is low nitrogen fertiliser, typical of the world’s poorest countries.

However, the researchers are not all gloomy. Genetic variations in crops show that some strains can still benefit despite increased temperatures. If new crop cultivars are developed, then the future could be brighter, but work needs to start now, the scientists say. − Climate News Network

Rewilded farmland can save money − and the Earth

November 2nd, 2020, by Tim Radford

Producing food and caring for the planet can be hard to combine. 

Image: By François Germain on Unsplash

To save civilisation, try rewilded farmland. But that salvation depends on which land goes back to forest and savannah.

LONDON, 2 November, 2020 − An international consortium of scientists has worked out − once again − how to conserve life on the planet and absorb dramatic quantities of the atmospheric carbon that is driving potentially calamitous climate change: go for rewilded farmland, fields of crops and livestock returned to prairie and forest. And they have identified the most cost-effective way to do it.

Global salvation requires the world’s nations to do simply what they have already undertaken to do: restore 15% of cultivated land to natural forest, grassland, shrubland, wetland and desert ecosystem.

If such restoration happened in the highest priority zones, then almost two-thirds of the wild things now threatened with imminent extinction could survive.

And the restored wilderness that would protect them would also start absorbing atmospheric carbon at an accelerating rate: it could sequester an estimated 229 billion tonnes of the greenhouse gas carbon dioxide (CO2). This is almost a third of all the CO2 spilled into the atmosphere by coal, oil and gas combustion in the last 200 years.

All that would be possible if the world’s nations delivered on vows made 10 years ago in Japan, to restore 15% of ecosystems worldwide. If the 196 nations that signed up went further, and restored a carefully chosen 30%, they could save more than 70% of the million or so species sliding towards extinction, and absorb 465 billion tonnes of CO2: almost half of all the extra atmospheric carbon loaded into the atmosphere by human societies since the Industrial Revolution.

Two provisos

“Pushing forward on plans to return significant sweeps of nature to a natural state is critical to preventing ongoing biodiversity and climate crises from spinning out of control,” said Bernado Strassburg, of the Pontifical Catholic University in Brazil, who led the study.

“We show that if we’re smarter about where we restore nature, we can tick the climate, biodiversity and budget boxes on the world’s urgent to-do list.”

There is a catch. To be most effective, and for the lowest costs, nations would have to work together.

Right now, scientists report in the journal Nature, each nation has undertaken to restore 15% of its wilderness. But to save the greatest number of species, and absorb the highest levels of carbon, with the lowest cost to farmland and food security, humankind would have to assess the world as a whole, and restore those ecosystems that would serve the goals most effectively.

There is a second catch: barely a month ago, a UN report confirmed that although 196 nations agreed on 20 targets to protect biodiversity − to be achieved by 2020 − a decade ago, there has been “partial progress” in just six of them. The million species then threatened with extinction are still threatened.

Potential ignored

“Many good things are happening around the world and these should be celebrated and encouraged,” said Elizabeth Maruma Mrema, executive secretary of the Convention on Biological Diversity.

“Nevertheless the rate of biodiversity loss is unprecedented in human history, and pressures are intensifying. Earth’s living systems as a whole are being compromised.”

And that threat starts with the green things on which all life depends: in September, the Royal Botanic Gardens at Kew in London published a new study on ways to identify and care for the plants and fungi that underwrite survival for what could be seven million or more species alive on the planet, and more than seven billion humans.

The study, involving 210 scientists in 42 countries, said Alexandre Antonelli, director of science at the Royal Botanic Gardens, paints a picture “of a world that has turned its back on the incredible potential of plant and fungal kingdoms to address some of the biggest challenges we face.

“We have particularly earmarked the gaps in our knowledge, the changes we are seeing, the species being named new to science and the shocking pace of biodiversity loss.”

“The rate of biodiversity loss is unprecedented in human history, and pressures are intensifying. Earth’s living systems as a whole are being compromised”

The most recent finding builds on the drive not just to fulfil the obligations undertaken 10 years ago, but to identify the very best ways to fulfil them, so as to benefit the greatest number of people.

It delivers the evidence that restoration in the most carefully chosen regions would have the most profound impact: put simply, restoration could be 13 times more cost-effective if it happened in what the Nature researchers have identified as the highest priority locations.

They used sophisticated mathematical tools and detailed geographic data to take a closer look at the 28.7 million square kilometres of natural wilderness that have been converted to farmland: 54% of these were originally forest, 25% grasslands, 14% shrublands, 4% arid lands and 2% wetland.

They then tested these areas against three considerations: their value as habitat, their capacity for carbon storage and their cost-effectiveness. And they came up with recommendations that would deliver 91% of the potential benefit for plants and animals of the wilderness and 82% of the climate mitigation benefit, and reduce costs by 27%.

And then they considered the nation-by-nation approach: were each country to restore 15% of its own forests, the biodiversity boon fell by 28%, the climate benefits by 29%, while the costs would rise by 52%.

Vital partnership

They then considered the impact on the world’s food supplies, to find that 15.78 million sq kms, or 55% of wilderness converted to farmland, could be restored without squeezing food supplies, always providing nations encouraged what they call the “sustainable intensification” of farming, along with a reduction in food waste and a move away from meat and dairy products.

The findings simply extend a procession of such outcomes by other teams. It has been a given for decades that, if forest and other ecosystems become farmland, greenhouse gas levels rise. If wilderness is restored, then the carbon dioxide levels in the atmosphere will fall.

Researchers have repeatedly argued that simply planting more trees could have a dramatic impact on global heating; that a switch towards a plant-based diet could help stem biodiversity loss and reduce emissions; and that without concerted global action, precious ecosystems could collapse altogether.

They have over and over again confirmed that conservation delivers real rewards. And they have pointed out that although nations have promised to act, such promises have not always been kept. The latest study highlights the need for action to be concerted, and global.

“These results highlight the critical importance of international co-operation in meeting these goals,” Dr Strassburg said. “Different countries have different, complementary roles to play in meeting overarching global targets on biodiversity and climate.” − Climate News Network

Food system causes one third of greenhouse gases

November 13th, 2020, by Tim Radford

A New Zealand feedlot, 2020: Not good for the cattle, nor us, nor the planet.

 Image: By SAFE, via Wikimedia Commons

How we eat causes dangerous climate heating. It’s time to change not only our diet, but the entire global food system.

LONDON, 13 November, 2020 − If the nations of the world really want to limit climate change to the level agreed five years ago, it will not be enough to immediately abandon fossil fuels as the principal source of energy: the global food system demands radical overhaul.

Humans will have to make dramatic changes to every aspect of agriculture worldwide, to planetary diet and to much else besides.

That is because the global food system − everything from clearing land and felling forests for cattle ranches to the arrival of meat and two vegetables on a suburban family dinner plate − accounts for 30% of the world’s greenhouse gas emissions. And to contain global heating later this century to no more than 1.5°C above the levels that existed before the Industrial Revolution, urgent action is needed.

In Paris in 2015, 195 nations undertook to limit the planetary thermometer rise to “well below” 2°C. The undeclared target was 1.5°C. In the last century, the global temperature has already risen by 1°C, and at the present rate it’s heading for a potentially catastrophic 3°C or more rise by around 2100.

“Food is a much greater contributor to climate change than is widely known”

British and US scientists report in the journal Science that they looked at the challenge of feeding a global population that has almost trebled in one human lifetime, and could reach 9bn or even 10bn later this century.

They found that the greenhouse gas emissions from food production alone would by 2050 take the world to the 1.5°C target, and to 2°C by the end of the century.

In just the five years that separated 2010 from 2017, the global food system accounted for an average of 16 billion tonnes of carbon dioxide equivalent in emissions each year. If humans go on pursuing business as usual, then the cumulative emissions from the food system could add up to 1,365 billion tonnes.

Emissions on that scale from the food system alone would take the planet past the preferred 1.5°C limit some time between 2051 and 2063, and reach the 2°C limit by 2100.

Remedies at hand

“Food is a much greater contributor to climate change than is widely known,” said Jason Hill, of the University of Minnesota, and one of the authors. “Fortunately, we can fix this problem by using fertiliser more efficiently, by eating less meat and more fruits, vegetables, whole grains and nuts, and by making other important changes to our food system.”

The finding should come as no great surprise: global heating is driven by more than simply the return of carbon dioxide fossilised 300 million years ago as coal, oil and natural gas to the atmosphere with every touch of the accelerator, with every jet plane take-off, with every ignition of the electric light, the air conditioning system and the heating, and every turn of industrial machinery around the planet.

It is also fuelled by the devastating clearance of natural forest, grassland and marsh for grazing land or plantation, and the conversion of natural canopy to fodder crops to nourish the world’s domestic cattle and sheep.

Researchers have repeatedly pointed out that even a relatively simple shift to greater reliance on a plant diet could save on carbon emissions, protect the million or so species threatened with imminent extinction, and improve global health, all at the same time.

Multiple benefits

So the latest study offers a new way of spelling out the scale of the problem − a global challenge that could be resolved by concerted and coherent international action.

The researchers identified five strategies that, they believe, could both help limit climate change and improve human health, enhance air quality, reduce water pollution, slow extinction rates and make farms more profitable.

The challenge is to increase crop yields per hectare, reduce food waste, improve farm efficiency and switch to healthy calorie supplies based increasingly on plant crops.

“Even partially adopting several of these five changes would solve this problem as long as we start right now,” said David Tilman, another author, and an ecologist at the university’s College of Biological Sciences. − Climate News Network

Warming puts surviving great tits in jeopardy

November 19th, 2020, by Kieran Cooke

On the look-out: A Polish great tit.

 Image: By hedera.baltica from Wrocław, Poland, via Wikimedia Commons

Among the best loved and most frequent visitors to gardens in the UK and elsewhere, great tits face mounting problems.

LONDON, 19 November, 2020 – In the scientific community great tits are known as one of the most adaptable of bird species, showing considerable ability in adjusting to changing weather patterns and differing times of food supplies.

But latest research indicates that even these ever-enterprising and resilient birds are coming under growing pressure from global heating.

“Wildlife has shown a great ability to adapt to climate change”, Emily Simmonds, lead author of a study of great tits and their food supplies, told Climate News Network.

“So far the great tit has shown a remarkable degree of adaptation to changes in climate. The problem occurs when change happens too fast – then, at some point in the future, the species could become extinct.”

“Our projections suggest that current population stability could be masking a route to population collapse”

Research by Simmonds and her colleagues involved both complex mathematical modelling and extensive fieldwork. Its main focus was to establish how quickly great tits could adapt to changes in the supply of caterpillars or larvae, vital food for the birds’ hatchlings.

Differing climate scenarios were used. In warmer conditions spring can occur earlier, with trees coming into leaf sooner than usual. This, in turn, causes larvae that feed on plants and leaves to hatch out earlier.

The problem is that if at some stage great tits fail to keep pace with these changes, then there will be no food for the hatchlings.

“If greenhouse gas emissions are too high and there’s more warming, then great tits might not be able to adjust their breeding habits quickly enough in order to adapt to the earlier supply of larvae”, says Simmonds.

Too fast for survival

“So far it seems that the birds are coping, but if warming continues at its present pace then it could be too much for them.”

Simmonds, now at the Norwegian University of Science and Technology,  carried out her research at Oxford in the UK.

At Wytham Woods outside Oxford scientists have been recording the nesting and breeding habits of the great tit – Parus major – and the blue tit – Cyanistes caeruleus – since 1947. Up to 40 generations of birds have been marked in what is one of the longest-running ecological studies of wild animals in the world.

The recent study looked at great tits’ reproduction success rates, hatching dates and inheritance factors – the ability of one generation to pass on to the next changes in breeding and feeding patterns.

Safety threshold

Winter temperatures, rainfall patterns and the availability of food supplies under different climate projections were considered.

“The good news is that populations of great tits can survive and adapt to scenarios with lower or medium warming trends”, says Simmonds.

But the study found that if warming trends continue at present levels, with larvae appearing, by the end of the century, about 24 days earlier than at present, great tit populations could become extinct.

“Our projections suggest that current population stability could be masking a route to population collapse, if high greenhouse gas emissions continue”, the study says. – Climate News Network