Tropical deforestation threatens global food production

Chris Arsenault at the Thomson Reuters Foundation via Reuters: Tropical deforestation in the southern hemisphere is accelerating global warming and threatening world food production by distorting rainfall patterns across Europe, China and the U.S. Midwest, a study released on Thursday said.

By 2050, deforestation could lead to a 15 percent drop in rainfall in tropical regions including the South American Amazon, Southeast Asia and Central Africa, the study published in the journal Nature Climate Change said.

Much of the logging taking place is to clear land for agriculture. This can cause a vicious cycle, increasing global warming, lowering food production on farms which in turn leads to growers cutting down more trees for farmland, experts say. "When you deforest the tropics, those regions will experience significant warming and the biggest drying," Deborah Lawrence, a University of Virginia professor and the study's lead author, told the Thomson Reuters Foundation.

Removing trees and planting crops releases carbon dioxide into the atmosphere, contributing to global warming. At the same time, deforested areas are also less able to retain moisture, immediately altering local weather patterns. The study said if current deforestation rates persist in South America's Amazon rainforest, the region's soy production could fall by 25 percent by 2050....

Deforestation in Kalimantan, Indonesia, shot by Josh Estey/AusAID, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generric license 

Tropical trees absorb 2 billion tons of carbon yearly

Futurity via the University of Leeds (posted by Sarah Reed): Reducing deforestation in the tropics would significantly cut the amount of carbon dioxide emitted into the atmosphere by as much as one-fifth, research shows. In the first study of its kind, scientists have calculated the amount of carbon absorbed by the world’s tropical forests and the amounts of greenhouse gas emissions created by loss of trees, as a result of human activity.

Scientists analyzed data from previous studies, including satellite studies, to determine the amount of carbon absorbed and emitted by the world’s tropical forests in South and Central America, equatorial Africa, and Asia.

“Forest census data from an Amazon-wide network of forest plots, maintained by the Universities of Leeds and Oxford, played a critical part in the analysis,” says Professor Emanuel Gloor, a coauthor of the study from the School of Geography at the University of Leeds. The research appears in Global Change Biology.

The researchers found that tropical forests absorb almost two billion tons of carbon each year, equivalent to one-fifth of the world’s carbon emissions, by storing it in their bark, leaves, and soil.

However, an equivalent amount is lost through logging, clearing of land for grazing, and growing biofuel crops such as palm oil, soy beans, and sugar. Peat fires in forests add significantly to the greenhouse gas emissions. Researchers say emissions from tropical forests will increase as the climate warms, as rising temperatures accelerate the decay of dead plants and trees, giving off more carbon dioxide.

...“If we limit human activity in the tropical forests of the world, this could play a valuable role in helping to curb the rise in carbon dioxide in the atmosphere. Preventing further losses of carbon from our tropical forests must remain a high priority,” says Professor John Grace of the University of Edinburgh’s School of GeoSciences, who led the study....

Deforestation in Kalimantan, Indonesia, shot by Josh Estey of AusAID, Wikimedia Commons via Flickr, under the Creative Commons 2.0 license

Tropical and northern wetlands likely to blame for greenhouse gas increases

A press release from the University of Guelph: A surprising recent rise in atmospheric methane likely stems from wetland emissions, suggesting that much more of the potent greenhouse gas will be pumped into the atmosphere as northern wetlands continue to thaw and tropical ones to warm, according to a new international study led by a University of Guelph researcher.

The study supports calls for improved monitoring of wetlands and human changes to those ecosystems – a timely topic as the Intergovernmental Panel on Climate Change prepares to examine land use impacts on greenhouse gas emissions, says Prof. Merritt Turetsky, Department of Integrative Biology.

Turetsky is the lead author
of a paper published today in Global Change Biology based on one of the largest-ever analyses of global methane emissions. The team looked at almost 20,000 field data measurements collected from 70 sites across arctic, temperate and tropical regions. Agnieszka Kotowska, a former master’s student, and David Olefeldt, a post-doc at Guelph, also were among 19 study co-authors from Canada, the United States, the United Kingdom, Finland, Germany and Sweden.

One of the strongest greenhouse gases, methane comes from agriculture and fossil fuel use, as well as natural sources such as microbes in saturated wetland soils. The amount of atmospheric methane has remained relatively stable for about a decade, but concentrations began to rise again in 2007. Scientists believe this increase stems partly from more methane being released from thawing northern wetlands.

Scientists have assumed that wetland methane release is largest in the tropics, said Turetsky. “But our analyses show that northern fens, such as those created when permafrost thaws, can have emissions comparable to warm sites in the tropics, despite their cold temperatures. That’s very important when it comes to scaling methane release at a global scale.”....

US Fish and Wildlife Service photo of tundra in the Arctic

No ‘permanent El Niño,’ scientists say — and the tropics may get even hotter

Eric Gershon in the Yale News: New research by Yale University scientists challenges a long-standing paradigm for temperature variability in the Pacific Ocean, casting doubt on the existence of a past period of “permanent” El Niño-like conditions and suggesting that the tropics could grow markedly hotter.

“There’s good news and bad news about future global warming,” said Mark Pagani, professor of geology and geophysics at Yale and an author of the research, published April 4 in the journal Science. “The good news is that global warming does not drive the Pacific Ocean into a permanent El Niño-like condition with all the other regional climate impacts that come with that. The bad news is that the tropics will warm as we continue to add greenhouse gases to the atmosphere — and the recent past was probably much warmer than generally assumed.”

Modern El Niño conditions are characterized by unusually warm surface water in the eastern equatorial Pacific, and a very low overall equatorial Pacific temperature gradient. The quasi-periodic phenomenon’s effects on global weather patterns can be dramatic, including extreme rainfall in some places (Texas, for example) and drought elsewhere (Indonesia and Australia).

A conventional view holds that sea surface temperatures in the warmest part of the equatorial Pacific — the vast western “warm pool” — remained relatively constant for millions of years. Given that ocean temperatures elsewhere rose during this time, the warm pool’s stable temperature implied a tropical ocean “thermostat” or temperature control mechanism, Pagani said.

But in a new reconstruction of ancient Pacific sea surface temperatures covering 12 million years, Pagani and Yale doctoral candidate Yi Ge Zhang found that Pacific warm pool temperatures were notably higher 12 million years ago than previously thought — as much as 4°C warmer. Their results indicate that all parts of the Pacific warmed during past periods of global warming, suggesting greater variability of ancient ocean temperatures and the absence of any tropical temperature control mechanism or  “permanent El Niño-like” conditions....

Ruins at Orongo on Easter Island, shot by TravelingOtter, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license 

Roads: driving development or deforestation?

EurActiv: Roads in the tropics often go hand in hand with economic development. But the day before the International Day of Forests (21 March), an MEP and a number of scientists called for a response to the role they play in deforestation.

Ways of measuring forest destruction are becoming increasingly sophisticated. This week, an initiative from Mongabay, an environmental publication, and NASA’s Ames Research Center, won the prestigious Katerva Award for a Global Forest Disturbance Alert System to map the destruction of forests, on a quarterly basis.

The system uses satellite imagery to detect deforestation when it occurs, so that measures can be taken to investigate it before it expands. Similarly, satellite images have revealed the way forests can deplete soon after the construction of a road nearby.

“95% of forest loss occurs within 50 km of a road. Scientific reports and satellite imagery have demonstrated road building is a major driver of deforestation, from the Amazon to Indonesian and Congo Basin forests,” said Kriton Arsenis, a Greek MEP affiliated with the Socialists and Democrats in the European Parliament....

A dirt road in Brazil, shot by Figueirao, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license 

Rise in malaria forecast for tropical highlands

Maria Elena Hurtado in SciDev.net: More people may contract malaria in the tropical highlands of Africa, Asia and South America as global warming makes the climate in these areas more suitable for the disease’s transmission, according to a study.

While the study focuses on the effects of global warming, it notes that further studies will be needed to account for other factors that may influence the disease’s spread, including economic development, changes in human population patterns and adaptations in the mosquitoes that transmit malaria.

The authors of the paper, published this month in Proceedings of the National Academy of Sciences (3 February), used five existing malaria impact models to make predictions for the 2030s, 2050s and 208
0s.

The malaria models were run under four different carbon dioxide emissions scenarios developed by the Intergovernmental Panel on Climate Change. The researchers examined how easily disease would be transmitted and how many people would be at risk under the different scenarios.

They found that each of the five models predicted an extended the disease transmission season in the highland regions of eastern Africa, South Africa, central Angola, the plateau of Madagascar, central America, southern Brazil and the border area between India and Nepal....

A bucket of skeeters, shot by the National Institutes of Health

Sensitivity of carbon cycle to tropical temperature variations has doubled

A press release from the University of Exeter: The tropical carbon cycle has become twice as sensitive to temperature variations over the past 50 years, new research has revealed. The research shows that a one degree rise in tropical temperature leads to around two billion extra tonnes of carbon being released per year into the atmosphere from tropical ecosystems, compared with the same tropical warming in the 1960s and 1970s.

Professor Pierre Friedlingstein and Professor Peter Cox, from the University of Exeter, collaborated with an international team of researchers from China, Germany, France and the USA, to produce the new study, which is published in the leading academic journal Nature.

Existing Earth System Model simulations indicate that the ability of tropical land ecosystems to store carbon will decline over the 21st century. However, these models are unable to capture the increase in the sensitivity of carbon dioxide to tropical temperatures that is reported in this new study.

Research published last year by Professors Cox and Friedlingstein showed that these variations in atmospheric carbon dioxide can reveal the sensitivity of tropical ecosystems to future climate change. Taken together, these studies suggest that the sensitivity of tropical ecosystems to climate change has increased substantially in recent decades.

Professor Cox, from the College of Engineering, Mathematics and Physical Sciences said: “The year-to-year variation in carbon dioxide concentration is a very useful way to monitor how tropical ecosystems are responding to climate. The increase in carbon dioxide variability in the last few decades suggests that tropical ecosystems have become more vulnerable to warming”.

Professor Friedlingstein, who is an expert in global carbon cycle studies added: “Current land carbon cycle models do not show this increase over the last 50 years, perhaps because these models underestimate emerging drought effects on tropical ecosystems”.

The lead author of the study, Xuhui Wang of Peking University, added: “This enhancement is very unlikely to have resulted from chance, and may provide a new perspective on a possible shift in the terrestrial carbon cycle over the past five decades”....

A NASA diagram of the carbon cycle

Fungi are the rainforest 'diversity police'

A press release from the University of Exeter: A new study has revealed that fungi, often seen as pests, play a crucial role policing biodiversity in rainforests. The research, by scientists at Oxford University, the University of Exeter and Sheffield University, found that fungi regulate diversity in rainforests by making dominant species victims of their own success.

Fungi spread quickly between closely-packed plants of the same species, preventing them from dominating and enabling a wider range of species to flourish. “In the plant world, close relatives make bad neighbours,” said Dr Owen Lewis of Oxford University's Department of Zoology, who led the study. “Seedlings growing near plants of the same species are more likely to die and we now know why. It has long been suspected that something in the soil is responsible, and we've now shown that fungi play a crucial role. It's astonishing to see microscopic fungi having such a profound effect on entire rainforests.

“Fungi prevent any single species from dominating rainforests as they spread more easily between plants and seedlings of the same species. If lots of plants from one species grow in the same place, fungi quickly cut their population down to size, levelling the playing field to give rarer species a fighting chance. Plots sprayed with fungicide soon become dominated by a few species at the expense of many others, leading to a marked drop in diversity.”

...Scientists had suspected that fungus-like microorganisms called oomycetes might also play a part in policing rainforest diversity, but this now seems unlikely. Professor Sarah Gurr, of Biosciences at the University of Exeter, said: “Oomycetes are potent pathogens that can cause seeds and seedlings to rot, and were responsible for the 1840s potato famine. To see if they play a role in promoting rainforest biodiversity, we sprayed plots with a fungicide which protects plants against oomycetes called Ridomil Gold. It had no significant effect on the number of surviving species, suggesting that true fungi and not oomycetes are driving rainforest diversity.” The findings help to explain why tropical rainforests are so much more diverse than forests in temperate countries....

An 1898 drawing of an oomycete

Tropical forests mitigate extreme weather events

Terra Daily via SPX: Tropical forests reduce peak runoff during storms and release stored water during droughts, according to researchers working at the Smithsonian Tropical Research Institute in Panama. Their results lend credence to a controversial phenomenon known as the sponge effect, which is at the center of a debate about how to minimize flood damage and maximize water availability in the tropics.

During nearly 450 tropical storms, a team of visiting scientists from the University of Wyoming measured the amount of runoff from pastureland, abandoned pastureland and forested land as part of a large-scale land-use experiment in the Panama Canal watershed initiated by STRI.

Data collected by STRI staff and analyzed by University of Wyoming students indicate that land-use history has complex, long-term effects.

"We measured large differences in hydrologic response between watersheds with different land-use histories and land cover," said Fred Ogden, STRI Senior Research Associate and Civil Engineering Professor at the University of Wyoming.

"Our ultimate objective is to better understand these effects and include this improved understanding in a high-resolution hydrological model that we are developing to predict land-use effects in tropical watersheds."....

A forest in Belize, shot by Dennis Jarvis, Wikimedia Commons via Flickr,  under the Creative Commons Attribution-Share Alike 2.0 Generic license

Building climate expertise in poor countries

Roger Williamson in SciDev.net: A Nature study published this month shows, as SciDev.Net reported, that the tropics are likely to be the first region to face dramatic temperature rises. This is clearly terrible news. Many of the tropical African nations that will be hit by these increases are also among the world’s least developed countries (LDCs).

This news should focus our thinking. The problems the LDCs face in a climate-constrained world are complex and urgent.

In particular I am worried about one way of dealing with these problems: ‘participatory approaches’, which seek local people’s views about what development should look like. The problem is that, unless applied intelligently, such techniques could be a distraction from efforts to equip LDCs to deal with poverty and climate-related issues.

Take, for example, the participatory initiative A Million Voices, which sources views on sustainable development via the UN-created World We Want website. We do need a groundswell of support for new development goals beyond 2015, but the populism of such schemes is no substitute for scientific expertise.

No amount of conversation will decide which crops will produce food under which conditions. The stubborn reality is that, beyond a certain temperature and level of soil degradation, traditional crops simply will not grow. For advice on that, farmers don’t need A Million Voices — they only need a few. They need local experience and input from the crop specialist and the climate scientist.

But the LDCs are where climate science is the least robust. This is because, inevitably, meteorological data are weak in these countries. They have yet to devote considerable resources to collecting climate data, training (and retaining) staff and building expert national institutions, partly because they face many competing demands on limited budgets....

A peanut vendor in Ouagadougou, Burkina Faso, shot by Roman Bonnefoy (  Romanceor, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license

Tropical forest carbon absorption may hinge on an odd couple

Princeton University News: A unique housing arrangement between a specific group of tree species and a carbo-loading bacteria may determine how well tropical forests can absorb carbon dioxide from the atmosphere, according to a Princeton University-based study. The findings suggest that the role of tropical forests in offsetting the atmospheric buildup of carbon from fossil fuels depends on tree diversity, particularly in forests recovering from exploitation.

Tropical forests thrive on natural nitrogen fertilizer pumped into the soil by trees in the legume family, a diverse group that includes beans and peas, the researchers report in the journal Nature. The researchers studied second-growth forests in Panama that had been used for agriculture five to 300 years ago. The presence of legume trees ensured rapid forest growth in the first 12 years of recovery and thus a substantial carbon "sink," or carbon-storage capacity. Tracts of land that were pasture only 12 years before had already accumulated as much as 40 percent of the carbon found in fully mature forests. Legumes contributed more than half of the nitrogen needed to make that happen, the researchers reported.

These fledgling woodlands had the capacity to store 50 metric tons of carbon per hectare (2.47 acres), which equates to roughly 185 tons of carbon dioxide, or the exhaust of some 21,285 gallons of gasoline. That much fuel would take the average car in the United States more than half a million miles. Though the legumes' nitrogen fertilizer output waned in later years, the species nonetheless took up carbon at rates that were up to nine times faster than non-legume trees.

The legumes' secret is a process known as nitrogen fixation, carried out in concert with infectious bacteria known as rhizobia, which dwell in little pods inside the tree's roots known as root nodules. As a nutrient, nitrogen is essential for plant growth, but tropical soil is short on nitrogen and surprisingly non-nutritious for trees. Legumes use secretions to invite rhizobia living in the soil to infect their roots, and the bacteria signal back to initiate nodule growth. The rhizobia move into the root cells of the host plant and — in exchange for carbohydrates the tree produces by photosynthesis — convert nitrogen in the air into the fertilizer form that plants need. Excess nitrogen from the legume eventually creates a nitrogen cycle that benefits neighboring trees....

The diverse forest canopy on Barro Colorado Island, (Darien Jungle) Panama - Colombia, has provided ecologist Stephen Hubbell with years of data to test his controversial neutral theory of biodiversity and biogeography. Photos by Christian Ziegler, under the Creative Commons Attribution 2.5 Generic license

Global sea level rise dampened by Australia floods

NCAR/UCAR AtmosNews: When enough raindrops fall over land instead of the ocean, they begin to add up. New research led by the National Center for Atmospheric Research (NCAR) shows that when three atmospheric patterns came together over the Indian and Pacific oceans, they drove so much precipitation over Australia in 2010 and 2011 that the world’s ocean levels dropped measurably. Unlike other continents, the soils and topography of Australia prevent almost all of its precipitation from running off into the ocean.

The 2010-11 event temporarily halted a long-term trend of rising sea levels caused by higher temperatures and melting ice sheets. Now that the atmospheric patterns have snapped back and more rain is falling over tropical oceans, the seas are rising again. In fact, with Australia in a major drought, they are rising faster than before.

 “It’s a beautiful illustration of how complicated our climate system is,” says NCAR scientist John Fasullo, the lead author of the study. “The smallest continent in the world can affect sea level worldwide. Its influence is so strong that it can temporarily overcome the background trend of rising sea levels that we see with climate change.”

...As the climate warms, the world’s oceans have been rising in recent decades by just more than 3 millimeters (0.1 inches) annually. This is partly because the heat causes water to expand, and partly because runoff from retreating glaciers and ice sheets is making its way into the oceans. But for an 18-month period beginning in 2010, the oceans mysteriously dropped by about 7 millimeters (about 0.3 inches), more than offsetting the annual rise.

Fasullo and his co-authors published research last year demonstrating that the reason had to do with the increased rainfall over tropical continents. They also showed that the drop coincided with the atmospheric oscillation known as La Niña, which cooled tropical surface waters in the eastern Pacific and suppressed rainfall there while enhancing it over other portions of the tropical Pacific, Africa, South America, and Australia....

Heavy rains transformed Australia's landscape, as show in these two NASA satellite images of floodplains in southwestern Queensland. The first image was taken on September 26, 2009. By the time of the second image, on March 26, 2011, so much rain had been driven over Australia instead of falling on the ocean that global sea levels temporarily dropped. See the NASA extended caption for more details. (Image taken with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.)

Could China lead the race to save tropical forests?

Mike Davis in a press release on the Global Witness website: The world’s tropical forests – the planet’s lungs – are in rapid decline. Over the past 60 years over 60% of them have disappeared, while two-thirds of those that remain are fragmented. Demolition is driven, in large part, by logging, much of it illegal, which in turn paves the way for clear-cutting for plantations and agriculture.

...What would make China’s leaders care about their impact on tropical forests? The International Institute for Environment and Development (IIED)’s new ‘China-Africa Forest Governance Learning Platform’ report demonstrates the role increased dialogue can play. It showcases an innovative collaboration involving African civil society representatives and Chinese officials, aimed at ensuring that China’s demand for African timber brings benefits to local populations.

The report notes that African timber currently accounts for around 4% of China’s forest product imports, worth around US$1.3 billion. This demand is rising, and China’s role in the timber trade, globally, is pivotal. A study published by the Environmental Investigation Agency (EIA) last year estimated that China imported at least 18.5 million cubic metres of illegal logs and sawn timber in 2011, worth US $3.7 billion, constituting 10% of China’s total wood products imports. Chinese timber industry representatives contest some of EIA’s figures, but it is clear that alternative interpretations of available trade data cannot explain away a very serious problem. 

...There are strong arguments, grounded in self-interest, for China’s leaders to take a fresh look at the world’s tropical forests and their role in keeping them standing. These start with the commercial case for overhauling the way the Chinese timber products industry operates. An immediate risk to continued business as usual is the US Lacey Act amendments of 2008 and the 2013 EU Timber Regulation which prohibit the import of illegal wood products. If enforced, these laws will eat into the profit margins of Chinese firms who cannot demonstrate that their timber is clean....

A photo from the 1920s of a forest in Sumatra, Wikimedia Commons, from the Tropenmuseum Collection

Climate science boost with more accurate profile of tropical aerosols

CSIRO (Australia): The seasonal influence of aerosols on Australia's tropical climate can now be included in climate models following completion of the first long-term study of fine smoke particles generated by burning of the savanna open woodland and grassland.

Australia's biomass burning emissions comprise about eight per cent of the global total, ranking third by continent behind Africa (48 per cent) and South America (27 per cent).

Lead researcher, CSIRO's Dr Ross Mitchell, said fine particles generated by burning of the tropical savanna of Northern Australia are a globally significant aerosol source, with impacts on regional climate and air quality.

"Aerosols play a very important role in modulating climate, yet the knowledge of perhaps the most basic piece of information - the seasonal climatology - remains undetermined for many aerosol producing regions.

...."This foundation stone of the aerosol cycle allows hard-nosed testing and development of the aerosol modules used within global climate models," Dr Mitchell said...

Bush fire in central Queensland, shot by 80 trading 24, Wikimedia Commons, nder the Creative Commons Attribution-Share Alike 3.0 Unported license

Tropical ecosystems regulate variations in Earth's carbon dioxide levels

Space Daily via SPX: The study, published in the journal Proceedings of the National Academy of Sciences, found that a temperature anomaly of just 1+ C (in near surface air temperatures in the tropics) leads to a 3.5-Petagram (billion tonnes of carbon) anomaly in the annual CO2 growth rate, on average. This is the equivalent of 1/3 of the annual global emissions from the combustion of fossil fuels and deforestation together.

Importantly, the NASA Earth Exchange (NEX) study results provide scientists with a new diagnostic tool to understand the global carbon cycle as it undergoes major changes due to the influences of human activities.

NASA study co-author, CSIRO's Dr Pep Canadell, said that the study's 50-year analysis centred on temperature and rainfall patterns during El Nino years, when temperatures increase in tropical regions and rainfall decreases. An accompanying analysis assessed the effects of volcanic eruptions, which lead to decreased temperatures due to volcanic aerosols in the atmosphere.

"Our study indicates that carbon exchanges in tropical ecosystems are extremely sensitive to temperature, and they respond with the release of emissions when warmer temperatures occur".

..."Warming is the one thing that we know with most certainty will occur under climate change in the tropics, but there are still large uncertainties about the future precipitation in tropical regions," says Dr Canadell, who is also Executive Director of the Canberra-based Global Carbon Project....

Amazon deforestation, via NASA

Contemplating the Brazilian dilemma: Abundant grain but inadequate storage

Seed Daily via SPX: Tropical climates that allow for year-round farming would seem to be a tremendous economic advantage, but for corn and soybean farmers in the Brazilian state of Mato Grosso it also poses a problem-an abundance of grain followed by about a 10 percent postharvest loss, partially due to a lack of storage.

"There is a 34 percent undercapacity of soybean storage, and the situation is aggravated by the rapidly increasing production of second-crop maize," said University of Illinois agricultural economist Peter Goldsmith. "The worst situation occurs in northern Mato Grosso with a simulation of a full-maize second crop. The potential to succession crop is great and current levels of storage are low. There is clear evidence of a shortage of storage, particularly private and cooperative, as grain production rises in the state," he said.

Goldsmith conducted the research project, which was the first to employ Geographic Information System (GIS) software to map the coordinates of commercial, cooperative and private grain storage facilities in Mato Grosso.

"We created GIS coordinates for every facility, mapped them, and then overlaid how much the production there currently is and how much production there would be if farmers were to produce and store a second corn crop on 100 percent of the bean crop, in order to find the areas that had the most congestion and the least congestion," Goldsmith said.

...Goldsmith said that the information will help determine the best, most convenient locations for additional storage...

A farm in the Mato Grosso, shot by Pedro Biondi/ABr, Wikimedia Commons, under the Creative Commons Attribution 3.0 Brazil license

Biofuel boom could accelerate warming in tropics

Wagdy Sawahel in SciDev.net: The large-scale conversion of land for biofuel farming could make some tropical regions even warmer, according to a study. Researchers from the US-based Massachusetts Institute of Technology (MIT), assessed the impact on the climate of increased biofuel production by modelling two scenarios: one where trees are chopped down to plant biofuel crops and one where forests are maintained and fertilisers and irrigation are used to intensify the production of biofuel crops.

They found that both scenarios have a negligible impact on global warming. For example, in the first scenario the additional cropland reflects more sunlight, counterbalancing the warming associated with fewer trees and higher greenhouse gas concentrations. Also, in both scenarios, increasing the proportion of biofuels used would reduce warming by using fewer fossil fuel-based energy sources. But their findings also point to significant regional differences.

Willow Hallgren, a researcher at MIT's Center for Global Change Science, tells SciDev.Net that the real significance of the study is that it reveals that energy policies promoting large-scale biofuel plantations as a way of cutting carbon emissions will exacerbate existing warming trends in the tropics. Hallgren says that the study differs from others looking at the climate impacts of biofuels because it incorporates "numerous 'real world' determinants of where and how much biofuel crops are grown".

The areas where this regional warming would occur are located in the Amazon basin and in central and western Africa, she says.  The policy in which the biofuel expansion is embedded determines how much the local climate will warm, says Hallgren. "If you protect tropical forests, you greatly lessen this regional warming, which would likely have significant ecological, economic and social impact on people living in those regions," she says...

African grasslands, plus baobab, shot by Harvey Barrison, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

Rainforests can take the heat

Smithsonian Tropical Research Institute: South American rainforests thrived during three extreme global warming events in the past, say paleontologists at the Smithsonian Tropical Research Institute. No tropical forest in South America currently experiences average yearly temperatures of more than 84 degrees Fahrenheit (29°C). But by the end of this century, average global temperatures are likely to rise by another 1-7 (0.6-4°C) degrees, leading some scientists to predict the demise of the world’s most diverse terrestrial ecosystem.

Carlos Jaramillo, staff scientist, and Andrés Cárdenas, post-doctoral fellow, at the Smithsonian in Panama reviewed almost 6,000 published measurements of ancient temperatures to provide a deep-time perspective for the debate.

"To take the temperature of the past we rely on indirect evidence like oxygen isotope ratios in the fossil shells of marine organisms or from bacteria biomarkers," said Jaramillo.

When intense volcanic activity produced huge quantities of carbon dioxide 120 million years ago in the mid-Cretaceous period, yearly temperatures in the South American tropics rose 9-12 degrees (5-7°C). During the Paleocene-Eocene thermal maximum, 55 million years ago, tropical temperatures rose by 5-9 degrees (3-5°C) in less than 10,000 years. About 53 million years ago, temperatures soared again.

According to the fossil record, rainforests prospered under these hothouse conditions. Diversity increased. Because larger areas of forest generally sustain higher diversity than smaller areas do, higher diversity during warming events could be explained by the expansion of tropical forests into temperate areas. "But to our surprise, rainforests never extended much beyond the modern tropical belt, so something other than temperature must have determined where they were growing," said Jaramillo.

Their report, published in the Annual Review of Earth and Planetary Science, also refers to Smithsonian plant physiologist Klaus Winter’s finding that leaves of some tropical trees tolerate short-term exposure to temperatures up to 122-127 degrees (50-53°C). When carbon dioxide concentrations double, trees use much less water: further evidence that tropical forests may prove resilient to climate change.

Giant tree in Brazil's tropical forest, 1830, by Johann Moritz Rugendas

Scientists explore roots of future tropical rainfall

Space Daily via SPX: How will rainfall patterns across the tropical Indian and Pacific regions change in a future warming world? Climate models generally suggest that the tropics as a whole will get wetter, but the models don't always agree on where rainfall patterns will shift in particular regions within the tropics.

...Pedro DiNezio of the University of Hawaii and Jessica Tierney of Woods Hole Oceanographic Institution investigated preserved geological clues (called "proxies") of rainfall patterns during a time when the planet went into opposite gear and cooled dramatically in the last ice age. Land clues included charcoal from fires, and evidence of more sand dune activity and desiccated lakes, all indicating drier conditions, and evidence for higher lake levels and more pollen, indicating wetter conditions.

They also looked at records of seafloor sediments containing preserved shells of dead marine organisms; the shells contain higher or lower levels of a heavier isotope of oxygen, depending on the relative salinity of surface waters when the organisms were alive (less salty waters indicate more rainfall over the ocean).

...They then compared this evidence with results from 12 different mathematical climate models that simulate Earth's climate, which incorporate basic laws of physics, chemistry, and fluid dynamics surrounding air-sea-land-ice interactions. ...Their results surprised them: Only one model, developed by the Hadley Centre for Climate Prediction and Research in the England, reproduced the rainfall patterns they found from the geological evidence....

..."The good news is, the Hadley model combined with the geological evidence show a pathway to improve our ability to simulate and predict tropical rainfall in the future," Tierney said....

Rainfall from Cyclone Gonu in 2005, via NASA

ESA's next Earth Explorer satellite will map the tropics

Space Daily via ESA: ESA's Earth Observation Programme Board has selected 'Biomass' to become the seventh Earth Explorer mission. The innovative satellite aims to map and monitor one of Earth's most precious resources. Following the review of three candidate concepts at the Board's meeting, the Biomass mission concept is set to become the next in a series of satellites developed to further our understanding of Earth.

The satellite will be designed to provide, for the first time from space, P-band radar measurements that are optimised to determine the amount of biomass and carbon stored in the world's forests with greater accuracy than ever before.

This information, which is poorly known in the tropics, is essential to our understanding of the role of forests in Earth's carbon cycle and in climate change. Reliable knowledge of tropical forest biomass also underpins the implementation of the UN Reducing Emissions from Deforestation and forest Degradation (REDD+) initiative - an international effort to reduce carbon emissions from deforestation and land degradation in developing countries.

In addition, the measurements made by Biomass offer the opportunity to map the elevation of Earth's terrain under dense vegetation, yielding information on subsurface geology and allowing the estimation of glacier and ice-sheet velocities, critical to our understanding of ice-sheet mass loss in a warming Earth....