Climate link to amphibian decline

By Paul Rincon

The Columbia spotted frog is one of four species native to the park

Amphibian populations at Yellowstone - the world's oldest national park - are in steep decline, a major study shows.

The authors link this to the drying out of wetlands where the animals live and breed, which is in turn being driven by long-term climate change.

The results, reported in the journal PNAS, suggest that climate warming has already disrupted one of the best-protected ecosystems on Earth.

The park covers some 9,000 sq km (3,500 sq miles) in the western United States.

It lies mostly within the state of Wyoming, but spills over into Montana and Idaho. The area has been protected for more than a century; US congress granted Yellowstone national park status on 1 March 1872.

There is a pretty substantial signal of climate change in this region Sarah McMenamin, Stanford University

Visitors flock there to see its geysers, hot springs and bubbling mud pots, fuelled by ongoing volcanism. The park's vast forests and grasslands are also home to grizzly bears, wolves and bison.

But it is to much less conspicuous inhabitants - frogs, toads and salamanders - that scientists look for early indications of environmental degradation.

Four amphibian species are native to the park: the blotched tiger salamander (Ambystoma tigrinum melanostictum), the boreal chorus frog (Pseudacris triseriata maculata), the Columbia spotted frog (Rana luteiventris) and the boreal toad (Bufo boreas boreas).

The lower Lamar Valley in northern Yellowstone harbours countless small, fishless ponds - ideal for amphibian breeding and larval development.

Downward trend

Between 1992 and 1993, researchers surveyed 46 of these "kettle" ponds, which are re-filled in spring by groundwater and snow melt running down from the hills.

The "kettle" ponds are ideal habitats for amphibians

When a team from Stanford University in California repeated this survey between 2006 and 2008, the number of permanently dry ponds had increased four-fold.

Of the ponds that remained, the proportion supporting amphibians had declined significantly.

In addition, three of the four native amphibian species had suffered major declines in numbers. The number of species found in each location - the "species richness" - had also dropped off markedly.

Amphibians lay jelly-coated eggs that are unsuited to development on land, so they must return to water in order to spawn.

"They go through an aquatic period and a terrestrial period during their lives so they are very susceptible to changes in both types of environment," said co-author Sarah McMenamin, from the department of ecology and evolution at Stanford.

Changing landscape

The scientists saw no change in numbers of the boreal toad - which the IUCN conservation body lists as threatened. But this species was rare in 1992, as it is now, making it difficult to extract population trends.

The tiger salamander is among the affected species

Ms McMenamin, along with her colleagues Elizabeth Hadly and Christopher Wright, also analysed monthly temperature and precipitation data from Yellowstone, as well as satellite images of the park taken between 1988 and 2008.

These data revealed that decreasing rainfall and increasing temperatures during the warmest months of the year have significantly altered the landscape.

Drought is now more common and more severe than at any time in the past century, the researchers say.

"There is a pretty substantial signal of climate change in this region," Ms McMenamin told BBC News.

Yellowstone is famous for its geysers, such as Old Faithful

"Snow pack during the winter is decreasing - which other studies have documented - and the regional aquifer is drying up as a result of these large-scale climate changes.

"These ponds are changing, the environment is changing, the landscape is drying up and the amphibians no longer have a place to breed. It's disturbing."

Amphibian populations are in crisis worldwide: pollution, diseases such as chytrid fungus and rana virus, invasive species, UV radiation and habitat destruction all contribute to the problem.

Climate change might affect amphibian populations in numerous ways. In addition to drying out aquatic breeding habitats - preventing spawning - it could also make the land environment inhospitable to them.

Evidence suggests that a warming climate could also predispose amphibians to infection, particularly to chytrid fungus.

Paul.Rincon-INTERNET@bbc.co.uk

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Climate Change Destroying Walden Pond's Flowers

By Alexis Madrigal

Climate change is devastating the flowers of Walden Pond, picking off those species that cannot react to rising temperatures.

Comparing data meticulously gathered by Henry David Thoreau more than a century and a half ago with more recent observations, Harvard biologists report in the Proceedings of the National Academy of Sciences that more than a quarter of Walden's plant species have already been lost. And an additional 36 percent are in imminent danger, including lilacs, roses and buttercups.

"It had been thought that climate change would result in uniform shifts across plant species, but our work shows that plant species do not respond to climate change uniformly or randomly," said co-author Charles Davis, a biologist at Harvard, in a release.

The Walden study shows that even small changes in temperature can have outsized impacts on plants that are evolutionarily adapted to fulfill ecological niches. Together with changes seen in other locations, like the unprecedented pine beetle damage in the West, the new work suggests that finely tuned biological systems are having a difficult time keeping up with the rapid pace of human-induced climate change.

The average temperature around Walden has risen by more than four degrees over the last century as increasing greenhouse gas concentrations from burning fossil fuels changed the earth's climate.

But the warming is not just mowing the forest down, it's shaping it as some plant species thrive under the new global conditions.

The earth is not a mere fragment of dead history, stratum upon stratum like the leaves of a book, to be studied by geologists and antiquaries chiefly, but living poetry like the leaves of a tree, which precede flowers and fruit — not a fossil earth, but a living earth.
Henry David Thoreau -- Walden

"Most strikingly, species with the ability to track short-term seasonal temperature variation have fared significantly better under recent warming trends," the authors write.

Although the design of the Walden study is simple, it depends on the value of Thoreau's rare pre-industrial data.

"Whenever you have an opportunity to get a dataset where someone who has made very careful efforts to observe things in a systematic way, it gives you a snapshot of a particular time period and lets you make comparisons," said Mark Schwartz, a world expert in phenology, the field of seasonal changes in living things, at the University of Wisconsin, Milwaukee.

Unfortunately, very few ecosystems have been recorded in such excruciating detail.

"We don't have a large number of datasets of this sort," Schwartz said. "Most of them are concentrated in Europe and in Asia. There are very few in North America."

For example, Isabelle Chuine at France's Center for Evolutionary and Functional Ecology, published a paper in Nature using detailed grape harvest records in Burgundy dating from as far back as 1370. Schwartz also noted that many European weather services record phenological data along with their weather measurements, while American weather stations do not. As a result, Americans know less about when our plants bloom than many other countries.

But Schwartz is trying to change that by empowering Americans to contribute their own Thoreau-style data. He's the chair of the National Phenology Network, a new organization attempting to incorporate data from ecological stations, citizen scientists and other types of fieldwork.

Already, one of the NPN's efforts — Project BudBurst — has marshaled several thousand people to track the timing of plant flowerings in their backyards as they shift due to climate change.

Their data could not only benefit scientists of the present and future, but could aid in providing Americans with direct evidence of climate change, helping to create the political will necessary to address the nation's greenhouse gas emissions.

"When someone asks me about climate change, I say, 'You can go observe it in your own backyard,'" Schwartz said. "If you want to see what's happening, start taking records and see for yourself."

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Arctic Sea Ice Is Suddenly Getting Thinner As Well As Receding

Last winter, the thickness of sea ice in large parts of the Arctic fell by nearly half a metre (19 per cent) compared with the average thickness of the previous five winters. This followed the dramatic 2007 summer low when Arctic ice extent dropped to its lowest level since records began. (Credit: ESA)

Last winter, the thickness of sea ice in large parts of the Arctic fell by nearly half a metre (19 per cent) compared with the average thickness of the previous five winters. This followed the dramatic 2007 summer low when Arctic ice extent dropped to its lowest level since records began.

Up until last winter, the thickness of Arctic sea ice showed a slow downward trend during the previous five winters, but after the summer 2007 record low extent, the thickness of the ice also nose-dived. What is concerning is that sea ice is not just receding but it is also thinning.

Some scientists blamed the record summer 2007 ice extent low on unusually warm weather conditions over the Arctic, but this summer, sea ice extent reached the second lowest level since records began, even though the Arctic had a relatively cool summer. Dr Katharine Giles, who led the study and is based at the Centre for Polar Observation and Modelling at University College London – part of the National Centre for Earth Observation, says: “This summer’s low ice extent doesn’t seem to have been driven by warm weather, so the question is, was last winter’s thinning behind it?”

The team of researchers, including Dr Seymour Laxon and Andy Ridout, used satellites to measure sea ice thickness over the Arctic from 2002 to 2008. Winter sea ice in the Arctic is around two and half metres thick on average. Ice thickness can be calculated from the time it takes a radar pulse to travel from a satellite to the surface of the ice and back again.

The research - reported in Geophysical Research Letters - showed that last winter the average thickness of sea ice over the whole Arctic fell by 26cm (10 per cent) compared with the average thickness of the previous five winters, but sea ice in the western Arctic lost around 49cm of thickness. This region of the Arctic saw the North-West passage become ice free and open to shipping for the first time in 30 years during the summer of 2007.

The team is the first to measure ice thickness throughout the Arctic winter, from October to March, over more than half of the Arctic, using the European Space Agency’s Envisat satellite. Before this, Christian Haas of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, had discovered thinner ice in a small region around the North Pole. Whilst the overall loss of older, thicker ice led researchers to speculate that Arctic sea ice had probably thinned, this is the first time scientists have been able to say for definite that the ice thinning was widespread and occurred in areas of both young and old ice.

“The extent of sea ice in the Arctic is down to a number of factors, including warm weather melting it as well as currents and the wind blowing it around, so it’s important to know how ice thickness is changing as well as the extent of the ice,” added Giles.

The team will continue to monitor the thickness of the ice over this coming winter. Laxon says: “We’ll be keeping our eyes on the ice thickness this winter as it’ll be interesting to see what happens after a second summer of low ice extent.”

The Envisat satellite that provided the UCL scientists with their data doesn’t cover the whole of the North Pole. Because of the satellite’s orbit, there’s a hole north of 81.5 degrees, which is about 600 miles shy of the North Pole. But a team, including Laxon, at the Centre for Polar Observation and Modelling has designed a satellite – CryoSat-2 – to plug this hole.

CryoSat-2 is the first radar satellite specifically designed to measure ice thickness. It will do this with greater resolution than is possible with Envisat and so will give scientists a much more detailed picture of what is happening to ice in the Arctic. CryoSat-2 is being prepared for launch at the end of 2009.

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