Tag Archives: climate change

A more potent greenhouse gas than CO2, methane emissions will leap as Earth warms (Nature)

Freshwater wetlands can release methane, a potent greenhouse gas, as the planet warms. (Image source: RGBstock.com)

Freshwater wetlands can release methane, a potent greenhouse gas, as the planet warms. (Image source: RGBstock.com)

By Morgan Kelly, Office of Communications

While carbon dioxide is typically painted as the bad boy of greenhouse gases, methane is roughly 30 times more potent as a heat-trapping gas. New research in the journal Nature indicates that for each degree that the Earth’s temperature rises, the amount of methane entering the atmosphere from microorganisms dwelling in lake sediment and freshwater wetlands — the primary sources of the gas — will increase several times. As temperatures rise, the relative increase of methane emissions will outpace that of carbon dioxide from these sources, the researchers report.

The findings condense the complex and varied process by which methane — currently the third most prevalent greenhouse gas after carbon dioxide and water vapor — enters the atmosphere into a measurement scientists can use, explained co-author Cristian Gudasz, a visiting postdoctoral research associate in Princeton’s Department of Ecology and Evolutionary Biology. In freshwater systems, methane is produced as microorganisms digest organic matter, a process known as “methanogenesis.” This process hinges on a slew of temperature, chemical, physical and ecological factors that can bedevil scientists working to model how the Earth’s systems will contribute, and respond, to a hotter future.

The researchers’ findings suggest that methane emissions from freshwater systems will likely rise with the global temperature, Gudasz said. But to not know the extent of methane contribution from such a widely dispersed ecosystem that includes lakes, swamps, marshes and rice paddies leaves a glaring hole in climate projections.

“The freshwater systems we talk about in our paper are an important component to the climate system,” Gudasz said. “There is more and more evidence that they have a contribution to the methane emissions. Methane produced from natural or manmade freshwater systems will increase with temperature.”

To provide a simple and accurate way for climate modelers to account for methanogenesis, Gudasz and his co-authors analyzed nearly 1,600 measurements of temperature and methane emissions from 127 freshwater ecosystems across the globe.

New research in the journal Nature found that for each degree that the Earth's temperature rises, the amount of methane entering the atmosphere from microorganisms dwelling in freshwater wetlands — a primary source of the gas — will increase several times. The researchers analyzed nearly 1,600 measurements of temperature and methane emissions from 127 freshwater ecosystems across the globe (above), including lakes, swamps, marshes and rice paddies. The size of each point corresponds with the average rate of methane emissions in milligrams per square meter, per day, during the course of the study. The smallest points indicate less than one milligram per square meter, while the largest-sized point represents more than three milligrams. (Image courtesy of Cristian Gudasz)

New research in the journal Nature found that for each degree that the Earth’s temperature rises, the amount of methane entering the atmosphere from microorganisms dwelling in freshwater wetlands — a primary source of the gas — will increase several times. The researchers analyzed nearly 1,600 measurements of temperature and methane emissions from 127 freshwater ecosystems across the globe (above), including lakes, swamps, marshes and rice paddies. The size of each point corresponds with the average rate of methane emissions in milligrams per square meter, per day, during the course of the study. The smallest points indicate less than one milligram per square meter, while the largest-sized point represents more than three milligrams. (Image courtesy of Cristian Gudasz)

The researchers found that a common effect emerged from those studies: freshwater methane generation very much thrives on high temperatures. Methane emissions at 0 degrees Celsius would rise 57 times higher when the temperature reached 30 degrees Celsius, the researchers report. For those inclined to model it, the researchers’ results translated to a temperature dependence of 0.96 electron volts (eV), an indication of the temperature-sensitivity of the methane-emitting ecosystems.

“We all want to make predictions about greenhouse gas emissions and their impact on global warming,” Gudasz said. “Looking across these scales and constraining them as we have in this paper will allow us to make better predictions.”

Read the abstract.

Yvon-Durocher, Gabriel, Andrew P. Allen, David Bastviken, Ralf Conrad, Cristian Gudasz, Annick St-Pierre, Nguyen Thanh-Duc, Paul A. del Giorgio. 2014. Methane fluxes show consistent temperature dependence across microbial to ecosystem scales. Nature. Article published online before print: March 19, 2014. DOI: 10.1038/nature13164 and in the March 27, 2014 print edition.

Model anticipates ecological impacts of human responses to climate (Conservation Biology)

A Princeton University research team has created a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations. The tested their model by studying wheat and maize production in South Africa. (Image source: WWS)

A Princeton University research team has created a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations. The tested their model by studying wheat and maize production in South Africa. (Image source: WWS)

By B. Rose Huber, Woodrow Wilson School of Public and International Affairs

Throughout history, humans have responded to climate.

Take, for example, the Mayans, who, throughout the eighth and 10th centuries, were forced to move away from their major ceremonial centers after a series of multi-year droughts, bringing about agricultural expansion in Mesoamerica, and a clearing of forests. Much later, in the late 20th century, frequent droughts caused the people of Burkina Faso in West Africa to migrate from the dry north to the wetter south where they have transformed forests to croplands and cut the nation’s area of natural vegetation in half.

Such land transformations, while necessary to ensure future crop productivity, can themselves have large ecological impacts, but few studies have examined their effects. To that end, a Princeton University research team has created a model to evaluate how a human response to climate change may alter the agricultural utility of land. The study, featured in Conservation Biology, provides a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations.

“Humans can transform an ecosystem much more rapidly and completely than it can be altered by shifting temperature and precipitation patterns,” said Lyndon Estes, lead author and associate research scholar in the Woodrow Wilson School of International and Public Affairs. “This model provides an initial approach for understanding how agricultural land-use might shift under climate change, and therefore which currently natural areas might be converted to farming.”

Under the direction of faculty members Michael Oppenheimer and David Wilcove, both from the Wilson School’s Program in Science, Technology and Policy, and with the help of visiting student research collaborator Lydie-Line Paroz from ETH Zurich and colleagues from several other institutions, Estes studied South Africa, an area projected to be vulnerable to climate change where wheat and maize are the dominant crops.

Before determining how climate change could impact the crops, the team first needed to determine which areas have been or might be farmed for maize and wheat. They created a land-use model based on an area’s potential crop output and simulated how much of each crop was grown from 1979 to 1999 – the two decades for which historical weather data was available. They also calculated the ruggedness of each area of land, which is related to the cost of farming it. Taking all factors into account, the model provides an estimate of whether the land is likely to be profitable or unprofitable for farming.

To investigate any climate-change impacts, the team then examined the production of wheat and maize under 36 different climate-response scenarios. Many possible future climates were taken into account as well as how the crops might respond to rising levels of carbon dioxide. Based on their land-use model, the researchers calculated how the climate-induced productivity changes alter a land’s agricultural utility. In their analysis, they included only conservation lands – current nature reserves and those that South African conservation officials plan to acquire – that contained land suitable for growing one of the two crops either currently or in the future. However, Estes said the model could be adapted to assess whether land under other types of uses (besides conservation) are likely to be profitable or unprofitable for future farming.

They found that most conservation lands currently have low agricultural utility because of their rugged terrain, which makes them difficult to farm, and that they are likely to stay that way under future climate-change scenarios. The researchers did pinpoint several areas that could become more valuable for farming in the future, putting them at greater risk of conversion. However, some areas were predicted to decrease value for farming, which could make them easier to protect and conserve.

“While studying the direct response of species to climatic shifts is important, it’s only one piece of a complicated puzzle. A big part of that puzzle relates to how humans will react, and history suggests you don’t need much to trigger a change in the way land is used that has a fairly long-lasting impact. ” said Estes. “We hope that conservation planners can use this approach to start thinking about human climate change adaptation and how it will affect areas needing protection.”

Other researchers involved in the study include: Lydie-Line Paroz, Swiss Federal Institute of Technology; Bethany A. Bradley, University of Massachusetts; Jonathan Green, STEP; David G. Hole, Conservation International; Stephen Holness, Centre for African Conservation Ecology; and Guy Ziv, University of Leeds.

The work was funded by the Princeton Environmental Institute‘s Grand Challenges Program.

Read the abstract.

Estes LD, Paroz LL, Bradley BA, Green JM, Hole DG, Holness S, Ziv G, Oppenheimer MG, Wilcove DS. Using Changes in Agricultural Utility to Quantify Future Climate-Induced Risk to Conservation Conservation Biology (2013). First published online Dec. 26, 2013.

How will crops fare under climate change? Depends on how you ask (Global Change Biology)

Research image

Mechanistic (top row) and empirical (bottom row) simulations compared recent, or “baseline,” maize production in South Africa (1979-99) to projected future production under climate change (2046-65). While both models showed a reduction in output, the third column shows that the empirical model estimated a widespread yield loss of around 10 percent (in yellow), while the mechanistic model showed several areas of increased production (in green). (Image by Lyndon Estes)

Research image 2

For wheat, the mechanistic model (top row) projected greater wheat yields, while the empirical model (bottom row) suggested that wheat-growing areas would expand by almost 50 percent. (Image by Lyndon Estes)

By Morgan Kelly, Office of Communications

The damage scientists expect climate change to do to crop yields can differ greatly depending on which type of model was used to make those projections, according to research based at Princeton University. The problem is that the most dire scenarios can loom large in the minds of the public and policymakers, yet neither audience is usually aware of how the model itself influenced the outcome, the researchers said.

The report in the journal Global Change Biology is one of the first to compare the agricultural projections generated by empirical models — which rely largely on field observations — to those by mechanistic models, which draw on an understanding of how crop growth and development are affected by the environment. Building on similar studies from ecology, the researchers found yet more evidence that empirical models may show greater losses as a result of climate change, while mechanistic models may be overly optimistic.

The researchers ran an empirical and a mechanistic model to see how maize and wheat crops in South Africa — the world’s ninth largest maize producer, and sub-Saharan Africa’s second largest source of wheat — would fare under climate change in the years 2046 to 2065. Under the hotter, wetter conditions projected by the climate scenarios they used, the empirical model estimated that maize production could drop by 3.6 percent, while wheat output could increase by 6.2 percent. Meanwhile, the mechanistic model calculated that maize and wheat yields might go up by 6.5 and 15.2 percent, respectively.

In addition, the empirical model estimated that suitable land for growing wheat would drop by 10 percent, while the mechanistic model found that it would expand by 9 percent. The empirical model projected a 48 percent expansion in wheat-growing areas, but the mechanistic reported only 20 percent growth. In regions where the two models overlapped, the empirical model showed declining yields while the mechanistic model showed increases. These wheat models were less accurate, but still indicative of the vastly different estimates empirical and mechanistic can produce, the researchers wrote.

Disparities such as these aren’t just a concern for climate-change researchers, said first author Lyndon Estes, an associate research scholar in the Program in Science, Technology and Environmental Policy in Princeton’s Woodrow Wilson School of Public and International Affairs. Impact projections are crucial as people and governments work to understand and address climate change, but it also is important that people understand how they are generated and the biases inherent in them, Estes said. The researchers cite previous studies that suggest climate change will reduce South African maize and wheat yields by 28 to 30 percent — according to empirical studies. Mechanistic models project a more modest 10 to 19 percent loss. What’s a farmer or government minister to believe?

“A yield projection based only on empirical models is likely to show larger yield losses than one made only with mechanistic models. Neither should be considered more right or wrong, but people should be aware of these differences,” Estes said. “People who are interested in climate-change science should be aware of all the sources of uncertainty inherent in projections, and should be aware that scenarios based on a single model — or single class of models — are not accounting for one of the major sources of uncertainty.”

The researchers’ work relates to a broader effort in recent years to examine the biases introduced into climate estimates by the models and data scientists use, Estes said. For instance, a paper posted Aug. 7 by Global Change Biology — and includes second author and 2011 Princeton graduate Ryan Huynh — challenges predictions that higher global temperatures will result in the widespread extinction of cold-blooded forest creatures, particularly lizards. These researchers say that a finer temperature scale than existing projections use suggests that many cold-blooded species would indeed thrive on a hotter Earth.

Scientists are aware of the differences between empirical and mechanistic models, said Estes, who was prompted by a similar comparison that showed an empirical-mechanistic divergence in tree-growth models. Yet, only one empirical-to-mechanistic comparison (of which Estes also was first author) has been published in relation to agriculture — and it didn’t even examine the impact of climate change.

The solution would be to use both model classes so that researchers could identify each class’s biases and correct for it, Estes said. Each model has different strengths and weaknesses that can be complementary when combined.

Simply put, empirical models are built by finding the relationship between observed crop yields and historical environmental conditions, while mechanistic models are built on the physiological understanding of how the plant grows and reproduces in response to a range of conditions. Empirical models, which are simpler and require fewer inputs, are a staple in studying the possible effects of climate change on ecological systems, where the data and knowledge about most species is largely unavailable. Mechanistic models are more common in studying agriculture because there is a much greater wealth of data and knowledge that has accumulated over several thousand years of agricultural development, Estes said.

“These two model classes characterize different portions of the environmental space, or niche, that crops and other species occupy,” Estes said. “Using them together gives us a better sense of the range of uncertainty in the projections and where the errors and limitations are in the data and models. Because the two model classes have such different structures and assumptions, they also can improve our confidence in scenarios where their findings agree.”

Read the abstract.

Estes, Lyndon D., Hein Beukes, Bethany A. Bradley, Stephanie R. Debats, Michael Oppenheimer, Alex C. Ruane, Roland Schulze and Mark Tadross. 2013. Projected climate impacts to South African maize and wheat production in 2055: A comparison of empirical and mechanistic modeling approaches. Global Change Biology. Accepted, unedited article first published online: July 17, 2013. DOI: 10.1111/gcb.12325

The work was funded by the Princeton Environmental Institute‘s Grand Challenges Program.

How the ice ages ended (Nature)

by Catherine Zandonella, Office of the Dean for Research

Antarctica. Photo credit: Harley D. Nygren, NOAA

Antarctica. Photo credit: Harley D. Nygren, NOAA

A study of sediment cores collected from the deep ocean supports a new explanation for how glacier melting at the end of the ice ages led to the release of carbon dioxide from the ocean.

The study published in Nature suggests that melting glaciers in the northern hemisphere caused a disruption of deep ocean currents, leading to the release of trapped carbon dioxide from the Southern Ocean around Antarctica.

Understanding what happened when previous glaciers melted could help climate researchers make accurate predictions about future global temperature increases and their effects on the planet.

The evidence is strong that ice ages are driven by periodic changes in the amount of sunlight reaching the poles due to cyclic changes in Earth’s rotation and orbit. Yet scientists have been puzzled by evidence that although the timing of ice ages are best explained by changes in sunlight in the northern part of the globe, the warming at the end of ice ages occurred first in the southern hemisphere, with a rise in carbon dioxide levels appearing to be cued from the south.

The new study suggests that changes in ocean currents, connecting the north to the south through the deep ocean, were to blame.

As glaciers melted in the northern reaches of the globe (far upper left), the influx of freshwater, which is naturally less dense than salt-laden ocean water, reduced the normally strong sinking of water in that region. This allowed silicate-rich deep water to rise upward into the shallower ocean waters (upward blue arrows), stimulating the production of opal by diatoms, while warm surface water mixed downward (red arrows) into the southern-sourced deep water. The rising silicate-rich water drew dense cold water from near Antarctica, yielding a cycle of water movement (in yellow). The new circulation pattern caused the carbon dioxide stored in the deep water to be released to the atmosphere near Antarctica (far upper right). Image source: Daniel Sigman.

As glaciers melted in the northern reaches of the globe (far upper left), the influx of freshwater, which is naturally less dense than salt-laden ocean water, caused a reduction in the normally strong sinking of water in that region. This allowed silicate-rich deep water to rise upward into the shallower ocean waters (upward blue arrows), stimulating the production of opal by diatoms, while warm surface water mixed downward (red arrows) into the southern-sourced deep water. The rising silicate-rich water drew dense cold water from near Antarctica, yielding a cycle of water movement (in yellow). The new circulation pattern caused carbon dioxide stored in the deep water to be released to the atmosphere near Antarctica (far upper right). Image source: Daniel Sigman.

Part of this story was suggested more than a decade ago and is already accepted by many climate scientists: As glaciers in the north started melting, the influx of fresh water diluted the salty waters that today flow to the north from the tropics as an extension of the Gulf Stream. Normally, these salty waters become cool and sink into the deep ocean, forming cold and dense water that flows southward, and allowing more salty tropical water to take its place in a sort of ocean conveyor belt. But the influx of fresh water due to melting glaciers stalled the conveyor belt.

So how did this lead to changes in the southern hemisphere?

The new research suggests that the shutdown in northern sinking water allowed southern-sourced water to fill up the deep Atlantic, setting up a new ocean circulation pattern. This new circulation pattern brought deep-sea water, which was rich in carbon dioxide due to sunken dead marine algae, to the surface near Antarctica, where the gas escaped into the atmosphere and acted to drive global warming.  (See diagram.)

The researchers included investigators from ETH Zürich, Princeton University, the University of Miami, the University of British Columbia, and the University of Bremen and the Alfred Wegener Institute in Germany. The Princeton effort was led by Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences.

The team tracked these historic movements of water through the study of sediment cores that are rich in silicon dioxide, or opal. Tiny marine algae known as diatoms make their cell walls out of opal, and when the organisms die, their opal remains sink to the deep sea bed.

The researchers looked at opal in sediment core samples drilled from deep beneath the ocean floor off the coast of northwest Africa and Antarctica. The team found that each period of glacier melting, which occurred five times over the last 550 thousand years, corresponded to a spike in the amount of the opal in the sediment, signaling an increase in diatom growth. The timing of the opal spikes provides evidence that the deep, opal-rich waters in the south were drawn to the surface in response to new meltwater entering the northern ocean.

The mechanism clashes with a previously offered explanation of why the melting of the northern glaciers, or deglaciations, leads to the release of ocean carbon dioxide from the Southern Ocean – the theory that the melting glaciers in the north increased southern hemisphere westerly winds, which in turn caused upwelling of Southern Ocean deep waters. “While distinguishing between these alternatives is important,” says Sigman, “the greater challenge is to test and understand a premise that is shared by both of these scenarios: that ice age conditions around Antarctica caused the deep ocean to be sluggish and rich in carbon dioxide. If this was really how the ice age ocean operated, then it calls for us to reconsider how we expect deep ocean circulation to respond to modern global warming.”

Read the abstract.

A. N. Meckler, D. M. Sigman, K. A. Gibson, R. François, A. Martínez-García, S. L. Jaccard, U. Röhl, L. C. Peterson, R. Tiedemann & G. H. Haug. 2013. Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean. Nature 495 (7442), 495-498. doi:10.1038/nature12006. Published online 27 March, 2013.

This research used samples provided by the ODP, which is sponsored by the US National Science Foundation (NSF) and participating countries under the management of the Joint Oceanographic Institutions. XRF data were acquired at the XRF Core Scanner Lab at MARUM – Center for Marine Environmental Sciences, University of Bremen, with support from the DFG-Leibniz Center for Surface Process and Climate Studies at the University of Potsdam. Further support was provided by the US NSF through grant OCE-1060947 to D.M.S. and by NSERC and CFCAS to R.F.

Forecast is for more snow in polar regions, less for the rest of us (Journal of Climate)

Snowfall_figure

A new climate model predicts declines in snowfall in the U.S. over the next 70 years. Source: GFDL
Click on image to enlarge.

By Catherine Zandonella, Office of the Dean for Research

A new climate model predicts an increase in snowfall for the Earth’s polar regions and highest altitudes, but an overall drop in snowfall for the globe, as carbon dioxide levels rise over the next century.

The decline in snowfall could spell trouble for regions such as the western United States that rely on snowmelt as a source of fresh water.

The projections are the result of a new climate model developed at the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL) and analyzed by scientists at GFDL and Princeton University. The study was published in the Journal of Climate.

The model indicates that the majority of the planet would experience less snowfall as a result of warming due to a doubling of atmospheric carbon dioxide. Observations show that atmospheric carbon dioxide has already increased by 40 percent from values in the mid-19th century, and, given projected trends, could exceed twice those values later this century. In North America, the greatest reductions in snowfall will occur along the northeast coast, in the mountainous west, and in the Pacific Northwest. Coastal regions from Virginia to Maine, as well as coastal Oregon and Washington, will get less than half the amount of snow currently received.

In very cold regions of the globe, however, snowfall will rise because as air warms it can hold more moisture, leading to increased precipitation in the form of snow. The researchers found that regions in and around the Arctic and Antarctica will get more snow than they now receive.

The highest mountain peaks in the northwestern Himalayas, the Andes and the Yukon region will also receive greater amounts of snowfall after carbon dioxide doubles. This finding clashes with other models which predicted declines in snowfall for these high-altitude regions. However, the new model’s prediction is consistent with current snowfall observations in these regions.

The model is an improvement over previous models in that it utilizes greater detail about the world’s topography – the mountains, valleys and other features. This new “high-resolution” model is analogous to having a high-definition model of the planet’s climate instead of a blurred picture.

The study was conducted by Sarah Kapnick, a postdoctoral research scientist in the Program in Atmospheric and Oceanic Sciences at Princeton University and jointly affiliated with NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton, and Thomas Delworth, senior physical scientist at GFDL.

Read a plain-language summary of the article on GFDL’s web site.

Read the abstract.

Citation: Kapnick, Sarah B. and Thomas L. Delworth, 2013. Controls of Global Snow Under a Changed Climate. Journal of Climate.  Early online release published Feb. 6. http://dx.doi.org/10.1175/JCLI-D-12-00528.1

This work was supported by the Cooperative Institute for Climate Science, a collaborative institute between Princeton University and GFDL.

Spring may come earlier to North American forests (Geophysical Research Letters)

By Catherine Zandonella, Office of the Dean for Research

Trees in the continental U.S. could send out new spring leaves up to 17 days earlier in the coming century than they did before global temperatures started to rise, according to a new study by Princeton University researchers. These climate-driven changes could lead to changes in the composition of northeastern forests and give a boost to their ability to take up carbon dioxide.

Trees play an important role in taking up carbon dioxide from the atmosphere, so researchers led by David Medvigy, assistant professor in Princeton’s department of geosciences, wanted to evaluate predictions of spring budburst — when deciduous trees push out new growth after months of winter dormancy — from models that predict how carbon emissions will impact global temperatures.

The date of budburst affects how much carbon dioxide is taken up each year, yet most climate models have used overly simplistic schemes for representing spring budburst, modeling for example a single species of tree to represent all the trees in a geographic region.

In 2012, the Princeton team published a new model that relied on warming temperatures and the waning number of cold days to predict spring budburst. The model, which was published in the Journal of Geophysical Research, proved accurate when compared to data on actual budburst in the northeastern United States.

In the current paper published online in Geophysical Research Letters, Medvigy and his colleagues tested the model against a broader set of observations collected by the USA National Phenology Network, a nation-wide tree ecology monitoring network consisting of federal agencies, educational institutions and citizen scientists. The team incorporated the 2012 model into predictions of future budburst based on four possible climate scenarios used in planning exercises by the Intergovernmental Panel on Climate Change.

The researchers included Su-Jong Jeong, a postdoctoral research associate in Geosciences, along with Elena Shevliakova, a senior climate modeler, and Sergey Malyshev, a professional specialist, both in the Department of Ecology and Evolutionary Biology and associated with the U.S. National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory.

The team estimated that, compared to the late 20th century, red maple budburst will occur 8 to 40 days earlier, depending on the part of the country, by the year 2100. They found that the northern parts of the United States will have more pronounced changes than the southern parts, with the largest changes occurring in Maine, New York, Michigan, and Wisconsin.

The researchers also evaluated how warming temperatures could affect the budburst date of different species of tree. They found that budburst shifted to earlier in the year in both early-budding trees such as common aspen (Populus tremuloides) and late-budding trees such as red maple (Acer rubrum), but that the effect was greater in the late-budding trees and that over time the differences in budding dates narrowed.

The researchers noted that early budburst may give deciduous trees, such as oaks and maples, a competitive advantage over evergreen trees such as pines and hemlocks. With deciduous trees growing for longer periods of the year, they may begin to outstrip growth of evergreens, leading to lasting changes in forest make-up.

The researchers further predicted that warming will trigger a speed-up of the spring “greenwave,” or budburst that moves from south to north across the continent during the spring.

The finding is also interesting from the standpoint of future changes in springtime weather, said Medvigy, because budburst causes an abrupt change in how quickly energy, water and pollutants are exchanged between the land and the atmosphere. Once the leaves come out, energy from the sun is increasingly used to evaporate water from the leaves rather than to heat up the surface. This can lead to changes in daily temperature ranges, surface humidity, streamflow, and even nutrient loss from ecosystems, according to Medvigy.

Read the abstract.

Citation:

Jeong, Su-Jong, David Medvigy, Elena Shevliakova, and Sergey Malyshev. 2013. Predicting changes in temperate forest budburst using continental-scale observations and models. Geophysical Research Letters. Article first published online: Jan. 25, 2013. DOI: 10.1029/2012GL054431

This research was supported by award NA08OAR4320752 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce.

Gypsy moth caterpillar takes bite out of forest carbon storage (Environmental Research Letters)

Forests are important carbon dioxide storage mechanisms, but a voracious leaf-eating caterpillar is cutting into the trees’ capacity to remove the greenhouse gas from the atmosphere, according to new research by scientists at Princeton University, Rutgers University and the United States Forest Service.

The gypsy moth caterpillar, widespread in the northeastern United States, can wreak devastation on forests as it devours the leaves of oak, pine, and other tree species. The new research found that this defoliation has a significant detrimental effect on the ecosystem’s capacity to act as a carbon sink.

The study found that an oak-pine forest in the New Jersey pinelands hit by the gypsy moth every five years would store about one-third less of the above-ground carbon as an unharmed similar forest, according to David Medvigy, assistant professor of geosciences at Princeton University.

The research was conducted by Medvigy and Karina Schäfer, assistant professor of ecosystem ecology at Rutgers University as well as researchers from the US Forest Service: Kenneth Clark of the Silas Little Experimental Forest in New Jersey and Nicholas Skowronski of the Northern Research Station in West Virginia.

The research was published in the journal Environmental Research Letters. (Read the open access article.) A news article about the study can be found here.

Citation: Medvigy, D., K. L. Clark, N. S. Skowronskiand and K. V. R. Schäfer. 2012. Simulated impacts of insect defoliation on forest carbon dynamics. Environ. Res. Lett. 7 045703