Tag Archives: Desert zones

What happens when the world dries out

FOR IMMEDIATE RELEASE A warming world carries many threats, and now scientists have discovered that a change in atmospheric conditions could have serious consequences for soil chemistry LONDON, 1 November – A warmer, drier world will be bad news for those people who already live on the edge. Higher temperatures will do more than evaporate the soil moisture: they will alter the natural soil chemistry as well. Manuel Delgado-Baquerizo of the Universidad Pablo de Olavide, in Seville, Spain, and fellow scientists report in Nature that they looked  at soil samples from 224 dryland ecosystem plots in every continent except Antarctica. Drylands matter: they account for more than 40% of the planet’s land surface and they support more than 38% of its population. Drylands add up, in the dusty language of science, to the largest “terrestrial biome” of all. And even though on average more warmth will mean more evaporation, and therefore more water vapour in the atmosphere and more precipitation in some of those zones that already have ample rainfall, the pattern could be different in the arid lands. All the calculations so far indicate that these drylands will increase in area, and become drier with time. Already 250 million people are trying to scrape an increasingly meagre living from lands which are degrading swiftly, either because they are turning to desert, or because they are overgrazed.

Hard on microbes

But to make things worse, climate scientists predict that between 2080 and 2099, soil moisture will decrease by between 5% and 15% worldwide. And that in turn could have a profound effect on the levels of carbon and nitrogen nutrients naturally in the topsoils. What keeps soils alive, and productive, is the compost or humus of leaf litter, animal dung, withered roots and other decaying vegetation in the first metre or so of topsoil: this in turn feeds an invisible army of tiny creatures that recycle the nutrient elements for the next generation of plant life. But these microbes also need water to thrive. The consortium of researchers predicted that as the soils got drier, biological activity would decrease, but geochemical processes would accelerate. That is, nutrients that depended on little living things in the soil would drain away, but other elements – phosphorus among them – would increase, because they would be winnowed from the rock by mechanical weathering or erosion. The research team tested this argument with samples from 16 countries, including the Negev desert in Israel, the woodlands of New South Wales in Australia, the Altiplano of Peru, and the Pampas lowlands of Argentina.

Balance upset

These regions could all expect from 100mm of rainfall a year to 800 mm; all soil samples were analysed in the same laboratory in Spain. And as predicted, they revealed an increasing imbalance: more phosphorus, less carbon and nitrogen as they became drier. Such a trend would actually feed back into global warming: ideally, more vigorous plant growth would absorb more carbon dioxide. But if vegetation wilts, and soils turn to dust over large areas of already parched land, then the carbon dioxide levels in the atmosphere will increase even more. “Plants need all of these elements, in the correct amounts, and at the right times, but increasing aridity will upset this balance, leading to a breakdown in essential soil processes,” said David Etheridge, of the University of New South Wales, one of the authors. “As the world’s population grows, people will increasingly rely on marginal lands – particularly drylands – for production of food, wood and biofuels. But these ecosystems will be severely affected by imbalances in the cycle of carbon, nitrogen and phosphorus.” – Climate News Network

FOR IMMEDIATE RELEASE A warming world carries many threats, and now scientists have discovered that a change in atmospheric conditions could have serious consequences for soil chemistry LONDON, 1 November – A warmer, drier world will be bad news for those people who already live on the edge. Higher temperatures will do more than evaporate the soil moisture: they will alter the natural soil chemistry as well. Manuel Delgado-Baquerizo of the Universidad Pablo de Olavide, in Seville, Spain, and fellow scientists report in Nature that they looked  at soil samples from 224 dryland ecosystem plots in every continent except Antarctica. Drylands matter: they account for more than 40% of the planet’s land surface and they support more than 38% of its population. Drylands add up, in the dusty language of science, to the largest “terrestrial biome” of all. And even though on average more warmth will mean more evaporation, and therefore more water vapour in the atmosphere and more precipitation in some of those zones that already have ample rainfall, the pattern could be different in the arid lands. All the calculations so far indicate that these drylands will increase in area, and become drier with time. Already 250 million people are trying to scrape an increasingly meagre living from lands which are degrading swiftly, either because they are turning to desert, or because they are overgrazed.

Hard on microbes

But to make things worse, climate scientists predict that between 2080 and 2099, soil moisture will decrease by between 5% and 15% worldwide. And that in turn could have a profound effect on the levels of carbon and nitrogen nutrients naturally in the topsoils. What keeps soils alive, and productive, is the compost or humus of leaf litter, animal dung, withered roots and other decaying vegetation in the first metre or so of topsoil: this in turn feeds an invisible army of tiny creatures that recycle the nutrient elements for the next generation of plant life. But these microbes also need water to thrive. The consortium of researchers predicted that as the soils got drier, biological activity would decrease, but geochemical processes would accelerate. That is, nutrients that depended on little living things in the soil would drain away, but other elements – phosphorus among them – would increase, because they would be winnowed from the rock by mechanical weathering or erosion. The research team tested this argument with samples from 16 countries, including the Negev desert in Israel, the woodlands of New South Wales in Australia, the Altiplano of Peru, and the Pampas lowlands of Argentina.

Balance upset

These regions could all expect from 100mm of rainfall a year to 800 mm; all soil samples were analysed in the same laboratory in Spain. And as predicted, they revealed an increasing imbalance: more phosphorus, less carbon and nitrogen as they became drier. Such a trend would actually feed back into global warming: ideally, more vigorous plant growth would absorb more carbon dioxide. But if vegetation wilts, and soils turn to dust over large areas of already parched land, then the carbon dioxide levels in the atmosphere will increase even more. “Plants need all of these elements, in the correct amounts, and at the right times, but increasing aridity will upset this balance, leading to a breakdown in essential soil processes,” said David Etheridge, of the University of New South Wales, one of the authors. “As the world’s population grows, people will increasingly rely on marginal lands – particularly drylands – for production of food, wood and biofuels. But these ecosystems will be severely affected by imbalances in the cycle of carbon, nitrogen and phosphorus.” – Climate News Network

Desert yields clues to species’ survival

FOR IMMEDIATE RELEASE Research into one of the world’s oldest and driest deserts has unearthed evidence of the evolutionary timeline for species that have avoided extinction by adapting to dramatic climate change LONDON, June 26 − Biodiversity’s response to global warming is difficult to predict, but new research shows that species in the distant past have adapted to, and colonised, new and increasingly arid desert zones during a period of dramatic change. The less encouraging finding from the University of Chile scientists who have studied geological evidence from the Atacama-Sechura desert region − one of the Earth’s oldest and driest deserts − is that this adaptation takes about six million years. Any wildlife response to dramatic climate change – and the kind predicted in the worst case scenario for the 21st century is certainly in the dramatic category − depends on a very large number of factors.

Barriers to movement

These include how fast plants or small animals can move to cooler zones south or north; what barriers – such as mountain ranges, lakes, cities, motorways or farms − there might be to movement; and, of course, whether the ecosystem that supports any particular species can move at the same rate. Researchers have repeatedly warned of mass extinction under conditions of climate change, but it has been much harder to calculate the rates at which species might adapt or evolve, and populations recover, in new habitats. However, there are lessons to be learned from the recent geological past − long before Homo sapiens began to create extra difficulties for the rest of creation. Climate scientists can date changes in global temperatures with reasonable accuracy, palaeontologists can identify and date fossils of characteristic climate zone species with some precision, and geneticists can measure the rate at which DNA has evolved to adapt to new environments. This last technique now delivers a good measure of evolutionary timelines. Pablo Guerrero and fellow researchers at the University of Chile’s Department of Ecological Sciences report in the Proceedings of the National Academy of Sciences that they used geological evidence to put dates to the rainfall history of the ancient Atacama-Sechura desert region of Chile and Peru and the DNA readings to measure the rates at which three different kinds of plant and one genus of lizard evolved to colonise the new habitat.

Huge time lags

They found that these groups of plants and animals made their homes in the desert only in the last 10 million years – a good 20 million years after the onset of aridity in the region. There were also huge lags – from 4 million to 14 million years − between the time these creatures moved into the desert region and when they colonised the hyper-arid places. These ultra-dry parts of the region developed about 8 million years ago, but the most diverse of the plant group moved in only two million years ago. “Similar evolutionary lag times may occur in other organisms and habitats, but these results are important in suggesting that many lineages may require very long time scales to adapt to modern desertification and climate change,” the scientists in Chile report. − Climate News Network        

FOR IMMEDIATE RELEASE Research into one of the world’s oldest and driest deserts has unearthed evidence of the evolutionary timeline for species that have avoided extinction by adapting to dramatic climate change LONDON, June 26 − Biodiversity’s response to global warming is difficult to predict, but new research shows that species in the distant past have adapted to, and colonised, new and increasingly arid desert zones during a period of dramatic change. The less encouraging finding from the University of Chile scientists who have studied geological evidence from the Atacama-Sechura desert region − one of the Earth’s oldest and driest deserts − is that this adaptation takes about six million years. Any wildlife response to dramatic climate change – and the kind predicted in the worst case scenario for the 21st century is certainly in the dramatic category − depends on a very large number of factors.

Barriers to movement

These include how fast plants or small animals can move to cooler zones south or north; what barriers – such as mountain ranges, lakes, cities, motorways or farms − there might be to movement; and, of course, whether the ecosystem that supports any particular species can move at the same rate. Researchers have repeatedly warned of mass extinction under conditions of climate change, but it has been much harder to calculate the rates at which species might adapt or evolve, and populations recover, in new habitats. However, there are lessons to be learned from the recent geological past − long before Homo sapiens began to create extra difficulties for the rest of creation. Climate scientists can date changes in global temperatures with reasonable accuracy, palaeontologists can identify and date fossils of characteristic climate zone species with some precision, and geneticists can measure the rate at which DNA has evolved to adapt to new environments. This last technique now delivers a good measure of evolutionary timelines. Pablo Guerrero and fellow researchers at the University of Chile’s Department of Ecological Sciences report in the Proceedings of the National Academy of Sciences that they used geological evidence to put dates to the rainfall history of the ancient Atacama-Sechura desert region of Chile and Peru and the DNA readings to measure the rates at which three different kinds of plant and one genus of lizard evolved to colonise the new habitat.

Huge time lags

They found that these groups of plants and animals made their homes in the desert only in the last 10 million years – a good 20 million years after the onset of aridity in the region. There were also huge lags – from 4 million to 14 million years − between the time these creatures moved into the desert region and when they colonised the hyper-arid places. These ultra-dry parts of the region developed about 8 million years ago, but the most diverse of the plant group moved in only two million years ago. “Similar evolutionary lag times may occur in other organisms and habitats, but these results are important in suggesting that many lineages may require very long time scales to adapt to modern desertification and climate change,” the scientists in Chile report. − Climate News Network