NASA VIDEO: SCIENCECASTS: MUD MATTERS

U.S. FISH AND WILDLIFE VIDEL: OREGON RANCHERS PROTECT SAGEBRUSH HABITAT

CLIMATE CHANGE AND MAMMALS OF THE PAST

FROM:  NATIONAL SCIENCE FOUNDATION 

Understanding how ancestors of today's mammals responded to climate change
Research provides valuable insights for future environmental challenges
About 10 million years into the current Cenozoic Era, or roughly 56 million years ago, during a climate that was hot and wet, two groups of mammals moved from land to water. These were the cetaceans, which include whales, dolphins and porpoises, and the sirenians, with its sea cows, manatees and dugongs.

Over time, their bodies began to adapt to their new environment. They lost their hind limbs, and their forelimbs began to resemble flippers. Their nostrils moved higher on their skulls. The cetaceans became carnivores, eating fish and squid, while the sirenians became herbivores, living on sea grasses and algae.

"It's an interesting example of evolution, and a natural experiment you don't normally have," says Mark T. Clementz, an associate professor of paleontology in the University of Wyoming's department of geology and geophysics. "The changes are so extreme, you can't really ignore them. By studying these groups, we can tease out the main environmental factors that affect mammalian groups as they move into a new environment, and a new ecosystem."

The National Science Foundation (NSF)-funded scientist believes that understanding how the ancient ancestors of today's mammals responded to climate change will provide valuable insights that will help in dealing with environmental challenges.

"A better understanding of how these mammals responded in the past will give us a more informed idea of how they will respond to climate change in the future," he says. "This could benefit conservation efforts down the road, for example, what to look out for, what things could benefit these groups, and what will hurt them if climate change goes as we project."

Moreover, "these mammals are like data loggers," he adds. "You can infer what the environmental conditions of the past were like, and how they changed over time, and you can say something about how marine ecosystems have changed over time."

The primary goal of his project is to compare the evolutionary ecology of these two orders, the Cetacea and the Sirenia, in the context of Cenozoic climate change.

The Cenozoic Era is made up of two time periods, the Paleogene and the Neogene, with each of those divided into epochs, which are smaller subdivisions of geologic time.

"With the appearance of whales and sea cows in the Early Eocene [the second epoch of the Paleogene], the evolution and diversification of both groups occurred across major episodes of significant climate change as the Earth moved from the greenhouse conditions of the early Paleogene and into the icehouse conditions of the Neogene, and today," he says.

Clementz is conducting his research under an NSF Faculty Early Career Development (CAREER) award, which he received in 2009. The award supports junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education, and the integration of education and research within the context of the mission of their organization.

In order to evaluate the impact of climate change on each group, Clementz is examining fossil specimens of these ancient whales and sea cows as part of marine food webs, analyzing the stable isotopes of calcium, carbon, oxygen and strontium, with an emphasis on, among other things, each group's ecological status, including diet and salinity tolerance.

"When we look at the sirenians, it appears that they had a relationship with sea grasses, which are found only in salt water, that extends far in the past," he says, noting that it is unusual for mammals to move from land to saltwater without first spending a transitional period in freshwater. "The isotopes suggest they were feeding in sea grass beds while still capable of walking on land, and skipped the freshwater phase."

However, these conclusions may change upon examining recently acquired additional specimens.

"We now have some new fossils that imply that some sea cows might have been living in freshwater, but we haven't been able to fully analyze them yet," he says. Should that be the case, "it might have been a really fast transition," he says. "They might have spent a very short amount of time in freshwater, then moved quickly into a marine habitat."

The cetaceans, on the other hand, "do show a freshwater phase," he says.

Interestingly, the sirenians are very sensitive to environmental temperatures, staying where the water is warm--20 degrees Celsius (about 68 degrees Fahrenheit) or warmer. Today's global warming may, in fact, support them but possibly only to a certain extent.

"They like it warm," he says. "In the past, when conditions were warm, their range was greater. They went further north and further south. So, from a temperature perspective, today's climate change warming could benefit them. There is some question about how the climate could affect sea grasses and algae. It could be worse for them if it hurts their food supply."

Cetaceans, being more diverse, are more complicated, he says.

"They have about 80 different species, compared to the sirenians' four," he says. "They have been more successful at taking advantages of changes. It could be related to their diet of fish and squid. In cooler environments, they had higher food productivity They exploited those periods and diversified. Now that things are getting hotter, we're not sure how this will affect them."

As part of the grant's educational component, Clementz is taking an integrative big-picture approach to teaching K-12 and college students the concepts of evolution, ecology and climate change.

For example, he wrote a children's play that explains what occurred during the evolution of whales. Later, with the input of a choreographer and dance instructor, the play expanded to include a dance recital. It has been performed multiple times on campus, and many outside groups of young children have seen it.

"The children studied the movement of whales, then learned about their movements through dance," he says. "They got to see how whales move, and how it affects their bodies, and they got to dance, using dance moves that simulate whale movement. Visually, it really was stunning, and the kids learned a lot this way."

-- Marlene Cimons, National Science Foundation
Investigators
Mark Clementz
Related Institutions/Organizations
University of Wyoming

AMOUNT OF WATER TREES NEED AND THE CHANGING ATMOSPHERE

On the ground: looking into Harvard Forest's trees from a less lofty perch.  Credit: NSF Harvard Forest LTER Site

FROM:  NATIONAL SCIENCE FOUNDATION
Changing Atmosphere Affects How Much Water Trees Need

Spurred by increasing levels of atmospheric carbon dioxide, forests over the last two decades have become dramatically more efficient in how they use water.

Scientists affiliated with the National Science Foundation's (NSF) Harvard Forest Long-Term Ecological Research (LTER) site report the results in this week's issue of the journal Nature.

Harvard Forest is one of 26 such NSF LTER sites in ecosystems from deserts to grasslands, coral reefs to coastal waters, around the world.

Studies have long predicted that plants would begin to use water more efficiently, that is, lose less water during photosynthesis, as atmospheric carbon dioxide levels rose.

A research team led by Trevor Keenan and Andrew Richardson of Harvard University, however, has found that forests across the globe are losing less water than expected and becoming even more efficient at using it for growth.

Using data collected in forests in the northeastern United States and elsewhere around the world, Keenan and Richardson found increases in efficiency larger than those predicted by state-of-the-art computer models.

The research was done in collaboration with scientists from the USDA Forest Service, Ohio State University, Indiana University and the Karlsruhe Institute of Technology in Germany.

"This could be considered a beneficial effect of increased atmospheric carbon dioxide," said Keenan, the first author of the Nature paper.

"What's surprising is we didn't expect the effect to be this big. A large proportion of the ecosystems in the world are limited by water--they don't have enough water during the year to reach their maximum potential growth.

"If they become more efficient at using water, they should be able to take more carbon out of the atmosphere due to higher growth rates."

While increased atmospheric carbon dioxide may benefit forests in the short-term, Richardson emphasized that the overall climate picture would remain grim if levels continue to rise.

"We're still very concerned about what rising levels of atmospheric carbon dioxide mean for the planet," Richardson said.

"There is little doubt that as carbon dioxide continues to rise--and last month we just passed a critical milestone, 400 parts per million for the first time in human history--rising global temperatures and changes in rainfall patterns will, in coming decades, have very negative consequences for plant growth in many ecosystems around the world."

How do increasing carbon dioxide levels lead to more efficient water use?

The answer, Keenan said, is in the way photosynthesis works.

To take in the carbon dioxide they need, plants open tiny pores, called stomata, on their leaves. As carbon dioxide enters, however, water vapor is able to escape.

Higher levels of carbon dioxide mean the stomata don't need to open as wide, or for as long, so the plants lose less water and grow faster.

To take advantage of that fact, commercial growers have for years pumped carbon dioxide into greenhouses to promote plant growth.

To test whether such a "carbon dioxide fertilization effect" was taking place in forests, Keenan, Richardson and others turned to long-term data measured using a technique called eddy covariance.

This method, which relies on sophisticated instruments mounted on tall towers extending above the forest canopy, allows researchers to determine how much carbon dioxide and water are going into and out of the ecosystem.

With more than 20 years of data, the towers at the NSF Harvard Forest LTER site--which have the longest continuous record in the world--are an important resource for studying how forests have responded to changes in atmospheric carbon dioxide levels, scientists say.

"A goal of the NSF LTER program is understanding forest ecosystems and the basis for predicting fluxes of energy and materials in these ecosystems," said Matt Kane, program director in NSF's Division of Environmental Biology, "as well as distributions of forest biota as a result of global climate change."

"Findings from this study are important to our understanding of forest ecosystems--and how they can be managed more effectively now and in the future."

Though more than 300 towers like Harvard Forest's have sprung up around the globe, many of the earliest--and hence with the longest data records--are in the northeastern United States.

When the researchers began to look at those records, they found that forests were storing more carbon and becoming more efficient in how they used water.

The phenomenon, however, wasn't limited to a single region. When the scientists examined long-term data sets from all over the world, the same trend was evident.

"We went through every possible hypothesis of what could be going on, and ultimately what we were left with is that the only phenomenon that could cause this type of shift in water-use efficiency is rising atmospheric carbon dioxide," Keenan said.

Going forward, Keenan, who is now at Macquarie University in Sydney, Australia, is working to get access to data collected from yet more sites, including several that monitor tropical and arctic systems.

"This larger dataset will help us better understand the extent of the response we observed," he said.

"That in turn will help us build better models, and improve predictions of the future of the Earth's climate.

"Right now, all the models we have underrepresent this effect by as much as an order of magnitude, so the question is: What are the models not getting? What do they need to incorporate to capture this effect, and how will that affect their projections for climate change?"

The research was also supported by NOAA. Field measurements at the sites, which are part of the AmeriFlux network, have also been funded by the U.S. Department of Energy and the USDA Forest Service.

-NSF-