Rising CO2 is reducing nutritional value of food, impacting ecosystems

Among the myriad impacts climate change is having on the world, one in particular may come as a surprise: heightened atmospheric CO2 levels might be adversely affecting the nutritional quality of the food you eat. As carbon dioxide in the atmosphere continues to increase, you could end up eating more sugar and less of important minerals such as zinc, magnesium and calcium — without even realizing it. Those effects could also be reverberating up the food chain and altering ecosystems in as yet poorly understood ways.

For plants, a rise in atmospheric carbon dioxide actually boosts productivity by stimulating photosynthesis. They make more carbohydrate and grow larger — seemingly a good thing. But because other nutrients don’t increase and can’t keep pace with the augmented carbohydrate, this potential boon to our food supply isn’t all that it seems: plants end up having a higher carbohydrate to protein ratio, and relatively lower concentrations of minerals.

Put simply: atmospheric carbon dioxide acts as a sort of fertilizer to grow bigger, leafier plants, but those larger broccolis and lettuces actually contain less nutritional value per portion than their predecessors grown in the preindustrial, pre-fossil fuel world.

And that could be a problem for the world’s already malnourished people, for bees seeking protein-rich pollen so they can safely overwinter, and for ecosystems that could be thrown out of balance by changes in plant nutrition.

The human implications of these ongoing changes to our food supply came under the spotlight in April when the US Global Change Research Program (USGCRP) published a major report on the impact of climate change on human health. One of its key findings was that rising carbon dioxide will reduce the nutritional quality of food.

Read the full article on Mongabay

Rice fields in Kashmir, India. Staple crops such as rice and wheat are forecast to become less nutritious as a result of increasing carbon dioxide levels in the atmosphere. Photo courtesy of sandeepachetan.com travel photography on Flickr under CC BY-NC-ND 2.0 licenseRice fields in Kashmir, India. Staple crops such as rice and wheat are forecast to become less nutritious as a result of increasing carbon dioxide levels in the atmosphere. Photo courtesy of sandeepachetan.com travel photography on Flickr under CC BY-NC-ND 2.0 license

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Climate change a significant, growing threat to health, says US report

Climate change health effects are wide ranging and include negative impacts on air quality, mental health, nutrition, and insect and microbe transmitted diseases.

  • A Climate and Health Assessment presented at the White House by the US Global Change Research Program revealed wide-ranging climate change health impacts.
  • Every American is vulnerable, but low income people, certain ethnicities, Indigenous people, the young, elderly, and pregnant women are disproportionately at risk.
  • The report is meant to help policymakers generate and implement a proactive response to the many escalating and evolving health impacts due to climate change.

First published on Mongabay in April this year, you can read the full article here.

Ocean acidifying 10 times faster than anytime in the last 55 million years, putting polar ecosystems at risk

This article was written for Mongabay.com; the original can be found here.
An assessment of ocean acidification, presented at the UN Climate Change Conference in Warsaw in November 2013, starkly concluded that acidity is on track to rise 170 percent by the end of this century. As many key species are sensitive to changes in acidity, this would drastically impact ocean ecosystems, with effects especially pronounced in polar regions where the cold waters intensify acidification, and which are home to many organisms that are particularly vulnerable to acidification.The ocean acts as a giant sink for carbon, absorbing 24 million tons of CO2 from the atmosphere every day. Since industrialization, approximately 30 percent of anthropogenic (human generated) CO2 has been absorbed in this way. In the context of climate change this is incredibly important, as the amount of atmospheric CO2 is directly linked to global temperatures. But as CO2 is absorbed, the pH of the water decreases, and it becomes more acidic. Compared with pre-industrial levels, the ocean’s acidity has soared 26 percent, and will only increase as CO2 emissions rise. Not only will this likely injure marine ecosystems, but the more acidic the water becomes the less it is capable of absorbing carbon, thereby exacerbating CO2 emissions.

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Dr Ceri Lewis from the University of Exeter with sample bottles. Credit: Al Humphries- Catlin Arctic Survey

In addition to ecosystem damage, ocean acidification could bring about significant economic losses.

“People who rely on the ocean’s ecosystem services – often in developing countries – are especially vulnerable,” stated a press release by the International Council for Science.

The report’s authors represented the largest-ever gathering of ocean acidification scientists, with 540 experts representing 37 countries contributing to the discussion of acidification research. They found that the current rate of acidification is unprecedented, and is ten times faster than at any other time in the last 55 million years.

With the changing chemistry of the oceans comes a myriad of cascading effects. Coral reefs may start to erode faster than they are being built. Species that rely on calcification to build their shells and skeletons – using forms of calcium carbonate – may find acidic waters too corrosive to survive. This means the shellfish industry will likely suffer as mollusks (including mussels and oysters) are among the organisms most sensitive to acidification. And with other factors also changing at the same time, such as temperature, overfishing, and pollution levels, the cumulative effects are likely to be even more pronounced.

“Multiple stressors compound the effects of ocean acidification,” the authors wrote.

As CO2 is more soluble in colder water, the polar oceans are especially vulnerable. Not only are these regions suffering the greatest impacts of acidification today, they also act as an indicator of how acidification may impact warmer oceans in the future.

Dr Helen Findlay from Plymouth Marine Laboratory with the water sampler. Credit: Martin Hartley-Catlin Arctic Survey
Dr Helen Findlay from Plymouth Marine Laboratory with the water sampler. Credit: Martin Hartley-Catlin Arctic Survey

A key question in acidification research is the effect of acidity not only on individual species, but on the entire marine ecosystem. One way to assess this is by investigating how organisms at the bottom of the food chain are dealing with decreasing pH, since their health and abundance is vital for the health of the ecosystem as a whole.

An intrepid research expedition to the high Canadian Arctic in 2011 aimed to address this question by studying copepods, small crustaceans that form the dominant zooplankton in the Arctic Ocean. The investigations were led by scientists from the University of Exeter and the Plymouth Marine Laboratory in the UK, and their results were recently published in the Proceedings of the National Academy of Sciences (PNAS). They indicate that the range of pH levels copepods experience in their daily lives may predict the extent to which they will be able to cope with rises in acidity: those with the most specialized requirements may struggle to survive, while more generalist species may well be able to cope in the future.

“Our study found that some marine animals may not be able to survive the impact of ocean acidification, particularly the early-life stages,” said Ceri Lewis from the University of Exeter. “This unique insight into how marine life will respond to future changes in the oceans has implications that reach far beyond the Arctic regions.”

By teaming up with the Catlin Arctic Survey – a collaboration between explorers and scientists – a crucial gap in scientific knowledge could be addressed: what happens to these organisms under the ice during the Arctic winter? Conducting research during this time is extremely challenging, but understanding what happens then may be particularly important.

“If we don’t understand what goes on over the whole seasonal cycle (and there are very few winter studies) then we have no way of knowing how and what is changing, and why. In winter, there will still be sea ice even if it does eventually all melt in summer. It will always be dark and there will also be food limitations,” Helen Findlay, of the Plymouth Marine Laboratory, told mongabay.com.

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Drawings of different copepods. Photo in the US public domain.

“This is therefore an incredibly harsh time of year for any organism living in the Arctic, and as organisms are potentially most vulnerable at this time of year, we need to understand how they survive this time,” Findlay continued. “We were fortunate to get the opportunity to take part in the Catlin Arctic Survey, who wanted to team scientists up with explorers to undertake this difficult fieldwork. Without their support we wouldn’t have had the ice base facility and ability to go to the location in the high Arctic at that time of year.”

The team spent two months camping in sub-zero temperatures to undertake their research, which involved drilling through 1.6 meters (5.3 feet) of ice to collect samples of copepods to determine how their presence and abundance changes at various ocean depths. Although the conditions were almost unimaginably harsh, the experience was not without its rewards.

“Actually, it was amazing. It was quite strenuous both physically and mentally; keeping on top of everything for two months at constant temperatures below minus 25 ºC (-15 ºF) was quite a challenge. Especially as we were sleeping in unheated tents – just a sleeping bag and thermo-rest between us and the ice,” said Findlay. “On a trip like this the hours are long and you don’t really get a day off, but the rewards are that you are living and working in a beautiful environment with amazing wind and light conditions, gathering data that no-one else has collected before you.”

The researchers took samples from a range of depths down to 200 meters (650 feet) below the surface, and monitored the response of both adult and nauplii (early life stage) copepods to pH and CO2 levels that are predicted to occur in the next 100 years.

The sampling revealed distinct layers in the water chemistry, with highest CO2 and lowest pH at around 100 meters (325 feet) below the surface. Adult copepods from the endemic genus Calanus were found to migrate over the whole 200-meter range of sampling, and were thus exposed to a broad range of CO2 and pH conditions. Fortunately, these species did not suffer higher mortality in experiments that imitated future high acidity environments. But adults of the smaller, globally distributed copepod Oithona similis were found to be restricted to the upper 50 meters (150 feet) of the ocean, meaning that they live in a relatively constant environment in comparison with Calanus species. Survival was significantly reduced for Oithona similis in the experiments; its global distribution means that the implications of this could be far reaching.

A photo of a Copepod - Photo by Uwe Kils, provided under a Creative Commons Attribution-Share Alike 3.0 Unported license.
A photo of a Copepod – Photo by Uwe Kils, provided under a Creative Commons Attribution-Share Alike 3.0 Unported license.

Importantly, scientists only found the larval stages of all species in the upper layer of the water column. These responded in a similar way to adult Oithona similis, with reduced survival at high CO2 experimental treatments.

“It seems that copepods that are smaller, or earlier in their life stages, tend not to experience as wide ranging variability as large adults, and this makes them vulnerable to [environmental] shifts,” said Findlay. “The small stuff (copepods and their nauplii) are still very important parts of the food chain, with larger zooplankton and other organisms eating them, so indirectly a decline in these types of organisms could impact the food chain. More directly, if the nauplii (the early life stages) are not able to survive, then there won’t be any adults!”

The effect of increasing acidity and CO2 concentrations on individual copepods is not completely understood, but scientists believe a lack of food in the winter may cause higher mortality, as well as direct effects from pH and CO2 changes on their biological processes.

“These types of small simple organisms do not have very complicated internal structures like a blood system to regulate internal CO2 and pH conditions, both of which are important for things like enzyme activity, ion balance, and many other physiological processes,” said Findlay. “So we think that if we change the external pH or CO2 this influences the internal pH and CO2 conditions, causing a disruption to these normal physiological processes.”

“It’s a problem for some copepods because they don’t have complicated systems for dealing with this, that’s the same for many other organisms, not just copepods,” Findlay continued. “Some organisms are able to adjust proteins or ion exchange to counter-balance the shift, but this generally requires more energy.”

The researchers in the Arctic. Credit: Martin Hartley-Catlin Arctic SurveyThe researchers in the Arctic. Credit: Martin Hartley-Catlin Arctic Survey

Findlay’s findings mirror studies that have looked at temperature response in an array of organisms, and found the normal temperate range of a species can be used to predict its reaction to potential changes.

“The fact [that] this also applies to the pH or CO2 conditions makes sense because a lot of internal processes are dependent on the external pH and CO2 conditions and so if an organism experiences a wide range of these conditions we would expect it to be able to cope with that shift,” Findlay notes.

Although troubling for smaller and more specialized species, the potential for resilience among those that are more generalized is good news. However, the nature of future Arctic ecosystems remains uncertain.

“Certainly there will be species that can survive these changes,” said Findlay. “This is just one more piece of the jigsaw, and there are still many parts that need to be filled in. The ecosystems are likely to shift with both warming and acidification, indeed for Arctic species there are many stressors that will play a part in determining what the ecosystem will look like in the future.”

Citations:

  • IGBP, IOC, SCOR (2013). Ocean Acidification Summary for Policymakers – Third Symposium on the Ocean in a High-CO2 World. International Geosphere-Biosphere Programme, Stockholm, Sweden
  • Lewis, C. N., Brown, K. A., Edwards, L. A., Cooper, G., and Findlay, H. S. (2013) Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice. PNAS. DOI: http://www.pnas.org/cgi/doi/10.1073/pnas.1315162110

Myanmar faces new conservation challenges as it opens up to the world

This article was written for mongabay.com, and you can read the original version here.

For decades, one of Southeast Asia’s largest countries has also been its most mysterious. Now, emerging from years of political and economic isolation, its shift towards democracy means that Myanmar is opening up to the rest of the world. Myanmar forms part of the Indo-Burma biodiversity hotspot, and some of the largest tracts of intact habitat in the hotspot can be found here. With changes afoot, conservationists are looking to Myanmar as the best hope for protecting biodiversity in the region.

Scientists from the Wildlife Conservation Society (WCS) have undertaken an analysis of the environmental threats facing the country, recently published in AMBIO: A Journal of the Human Environment. By reviewing previous studies and analyzing potential changes in the climates of ecosystems across the country, the scientists have identified the primary conservation challenges facing the nation.

Fishing on Inle Lake.  Photo by Rhenda Glasco.Fishing on Inle Lake. Photo by Rhenda Glasco.

“For many years, Myanmar’s isolation has served to protect the biodiversity which has disappeared from many other regions in Southeast Asia,” said WCS’s Dr. Madhu Rao, lead author of the study. “Things are now changing rapidly for Myanmar, which will soon experience increasing economic growth and the myriad cascading effects of climate change on its forests and coastlines. The opportunity to protect the country’s natural heritage with a strategic and multi-faceted approach is now.”

Myanmar has extremely high biodiversity and a wealth of natural resources. In the north, Himalayan foothills extend down to forested valleys that are home to tigers, elephants, and rare birds. Mountains and plateaus give way to the central plains, and the great Ayeyarwady (Irrawaddy) river flows south, through a fertile valley, to a delta rich with mangroves and swamps before reaching the Andaman Sea. Some of these ecosystems, such as the lowland tropical forests and mangroves, are critically threatened elsewhere in the region. Myanmar is home to numerous endemic species, such as the white-browed nuthatch (Sitta victoriae), Myanmar snub-nosed monkey (Rhinopithecus strykeri), Burmese star tortoise (Geochelone platynota), and Burmese roof turtle (Batagur trivittata). In total, 233 globally threatened species are found here, 65 of them classified as Endangered, and 37 critically so.

However, the country’s large extent of intact habitat is relative to the extreme habitat loss seen in neighboring countries. Myanmar has not escaped habitat destruction, and in fact has suffered some of the highest rates of deforestation in the world. From 1990–2005, 18% of all forest area was lost to logging, much of it illegal. The lowland forests are most likely to suffer further future losses, as pressure on natural resources increases; commercial logging, agricultural expansion, and conversion to rubber and oil palm plantations are the main threats identified by the study.

“Location
Location of Myanmar (inset) within mainland Southeast Asia. Credit: Rao M. et al, 2013.

The scientists highlight weak environmental safeguards and low investment in conservation as two of the key factors that could make Myanmar especially susceptible to the effects of rapid economic development and climate change. Currently, overexploitation of both plant and animal species for subsistence and trade, along with habitat degradation and loss, are regarded as the primary threats to biodiversity in Myanmar. With international investments expected to increase dramatically in the near future, the authors anticipate “far-reaching negative implications for already threatened biodiversity and natural-resource dependent human communities.”

Myanmar’s system of protected areas is currently insufficient to safeguard biodiversity, with few large areas under protection, according to the researchers. In addition, the system as a whole does not represent the biological and geographic diversity within the country. Limited resources, both technical and financial, are to blame. However, Rao is hopeful that these issues can be overcome: “Myanmar is in a good position to begin addressing key technical and financial constraints – especially given the level of support that is being offered to the country by external entities. The time is right to fill policy gaps related to biodiversity and protected area management.”

“Given the current trajectories of economic interest in Myanmar, urgent conservation priorities include the need to expand and strengthen the existing protected area system, strengthening the legal and policy framework related to biodiversity and protected areas including the development of effective environmental safeguards and bolstering institutions responsible for protected area management,” Rao told mongabay.com. When examining the potential impacts of climate change, the scientists reached similar conclusions, advocating the protection of large, connected areas to “allow species or communities to track changing habitat conditions through space and time.”

Wetland systems, an important habitat for both wildlife and local communities, have already been degraded and are likely to suffer further from mining and hydroelectric development. The authors recommend the development of strict regulatory frameworks to limit their effects.

“The key to mitigating impacts of extractive industries is to develop and implement strong Environmental Impact Assessments and ensure that safeguards are adequately built into policies,” Rao said.

The study’s climate change analysis revealed that Myanmar is expected to experience high exposure and vulnerability to extreme weather events, as well as a range of impacts on human communities and biodiversity. The overall assessment predicts that sea level rises and storm surges will threaten coastal and estuarine ecosystems, changes in rainfall and temperature patterns will result in increased flooding and drought, and species’ ranges will shift to follow fluctuant habitats.

1004myanmar3
A new study by the Wildlife Conservation Society examines the potential implications of growing economic development and climate change on the biodiversity of Myanmar, home to wild places such as the Hukaung Valley. Photo courtesy of WCS Myanmar Program.

“The short and long-term impacts of climate change will aggravate existing threats to biodiversity in Myanmar through direct mechanisms and indirectly, through impacts on humans and their dependence on the products and services produced by terrestrial, freshwater and marine ecosystems,” the authors write.

James Watson, WCS’s Climate Change Program Director and co-author of the study, adds, “the threat of climate change implies the need to embrace ecosystem-based strategies that will enable people to be resilient and allow species to survive. With sensible planning, the people of Myanmar can aim to protect the key ecological services that will provide an important buffer for the likely effects of climate change that are already occurring.”

Recognizing the needs of local people and ensuring their involvement with conservation projects is vital. The authors state that greater engagement of local communities is an “essential requirement,” and that “appropriately designed conservation laws and land use policies are crucial to clarify how local communities can legally manage and benefit from natural resources.”

Rao explained further that “establishing clear zones for community use with their participation is not only important to ensure access of resources by communities but also helps spatially separate core areas without human use that could potentially act as source areas for wildlife. Ensuring local communities have tenure over their lands through clear land titles is an important mechanism to provide access to resources and simultaneously preventing the overexploitation of natural resources.”

What’s more, local people can be powerful advocates for their country’s biodiversity.

“There is a growing and dynamic group of civil society groups that are concerned with environmental issues and conservation,” Rao said. “Many of these have been organized around the threat of large, poorly planned infrastructure projects. Organizations such as Burma Rivers Network and the Dawei Development Association are increasingly sharing information and organizing the general public to be more informed and to participate in local and national decision making.”

The Ayeyarwady (Irrawaddy) River, Myanmar.  Photo by Rhenda Glasco.
The Ayeyarwady (Irrawaddy) River, Myanmar. Photo by Rhenda Glasco.

Furthermore, tourists are rediscovering Myanmar, and responsible ecotourism may offer an additional route to biodiversity conservation.

“Ecotourism can only offer conservation benefits if the ecotourism activity is well designed with mechanisms in place that involve strong linkages between ecotourism revenues and biodiversity conservation. Involving local communities in ecotourism and making explicit linkages to conservation targets can ensure benefits,” Rao said. “WCS is currently working with local communities in Mandalay to develop a community based ecotourism project linked to conservation of the critically endangered Irrawaddy dolphin.”

Although the study emphasizes the range of challenges facing Myanmar, it also highlights the great opportunities that exist to safeguard human livelihoods and biodiversity if action is taken. “Leaders of the Myanmar government have a chance to transform their country into a model for sustainable development,” said Joe Walston, Executive Director of WCS’s Asia Program. “Saving Myanmar’s natural wonders for posterity will rely on filling knowledge gaps and correctly anticipating the responses of environment and people in a changing world.”

Paper: Rao M., Htun S., Platt S.G., Tizard R., Poole C., Myint T., Watson J.E.M. 2013. Biodiversity conservation in a changing climate: A review of threats and implications for conservation planning in Myanmar. AMBIO: A Journal of the Human Environment. DOI: 10.1007/s13280-013-0423-5

Climate change pushing tropical trees upslope ‘exactly as predicted’

This article was first published on mongabay.com. You can read the original here.

Tropical tree communities are moving up mountainsides to cooler habitats as temperatures rise, a new study in Global Change Biology has found. By examining the tree species present in ten one-hectare plots at various intervals over a decade, researchers found that the proportion of lowland species increased in the plots at higher elevations. The study, which was undertaken in Volcan Barva, Costa Rica, adds to a growing body of evidence that climate change is having an impact on species range distributions.

As climate change leads to warmer temperatures, species must respond if they are to survive. One way to do this is to migrate to new habitats that become suitable (and away from old ones that become unsuitable); another way is to adapt to hotter temperatures, but the speed of climate change may be too fast for some species to evolve to keep up. In some cases, if their physiology permits it, species may be capable of tolerating increases in temperature, but the likelihood of this is unknown.

The researchers first turned to herbarium records to calculate the preferred temperature of thousands of tree species, by looking at the geographic location of sampling locations and the temperature ranges they encompassed. With the temperature preferences for each species known, it was then possible to calculate a ‘community temperature score’ for each of the ten study plots, by averaging the preferred temperatures of all species present. A high community temperature score indicated an abundance of species found in the hot lowlands, whereas a low community temperature score reflected the presence of high altitude species from cooler habitats.

Looking up at a giant tree in the Costa Rican rainforest Photo credit: Rhett A. Butler / mongabay.com

Looking up at a giant tree in the Costa Rican rainforest Photo credit: Rhett A. Butler / mongabay.com

Plots were monitored over the course of a decade, and in nine of the ten plots the community temperature score increased. This indicates a shift in species composition, with the relative abundance of lowland species increasing over time “exactly as predicted under climate-driven upward species migrations,” Kenneth Feeley, lead author of the study with Florida International University and Fairchild Tropical Botanic Garden, told mongabay.com.

These changes corresponded to a mean thermal migration rate of 0.0065°C per year. However, over the past 60 years regional warming has been 0.0167°C per year, so the average migration rate observed across plots is not fast enough to keep up with the rate of warming. Still, encouragingly, when looked at individually, migration in 4 of the 10 plots did keep pace with regional warming.

Changes in species composition can be the result of different processes: species abundance can change without shifts in the overall range distribution, ranges can shift, and ranges can expand or contract. Identifying which of these underlies changes in species composition is important, because “depending on which of these processes is occurring, predictions for the future of ‘migrating species’ will vary from positive (under range expansions), to neutral (under range shifts) to dire (under range contractions),” Feeley explains.

To examine the specific causes of the compositional shifts in the study plots, the researchers measured stem growth, recruitment (the establishment of new trees), and mortality. They found that the main driver behind the increase in the relative abundance of lowland species upslope was in fact the disproportionate death of higher elevation species.

“Our results indicate that dieback is happening much faster than expansion. This means that species’ ranges will shrink. As ranges shrink, species will be more and more prone to extinction,” Feeley said.

Forested mountains in Costa Rica, where tropical trees communities are changing in response to climate change. Photo credit Kenneth Feeley

Forested mountains in Costa Rica, where tropical trees communities are changing in response to climate change. Photo credit Kenneth Feeley

An earlier study by Feeley and colleagues investigated related questions in the Peruvian Andes and came to similar conclusions, suggesting that their findings may be generally applicable across the tropics.

“The rates of migration that we have documented for the forests of Costa Rica are remarkably similar to what we found in the Peruvian Andes. The rates are also fairly close to the maximum rates of migration recorded for tropical trees during the warming period that followed the last glacial maximum. As such, it appears that what we are observing is trees moving at their fastest,” Feeley said. “In the past, this was fast enough; it is not fast enough now and it certainly won’t be fast enough in the future,”

While range contractions increase the likelihood of extinction for individual species, they also have a broader impact on patterns of biodiversity.

“As species experience dieback at the trailing edges of their distributions due to temperatures becoming intolerably hot, we will get decreases in local diversity through a process that has been termed ‘biotic attrition’,” Feeley said. If species are able to shift their ranges upslope, and not just suffer dieback in the lowlands, “then we may expect an increase in alpha (local) diversity in the mountains over long time periods as large numbers of species move up out of the lowlands and into the highlands. In this case, the real losses of biodiversity are expected in the lowlands where there is no known pool of ‘hot-adapted’ species waiting to fill in the lowlands after the existing species emigrate.”

Migrating to track climate change – either by moving up mountainsides or by moving towards the poles – is not easy: temperature is not the only factor that determines whether a habitat is suitable for a species, it is just the simplest to study in order to predict how species might respond to our warming world.

“Other climatic factors such as precipitation and seasonality can be hugely important for some species as can other non-climatic factors such as soil type and slope. Furthermore, biotic factors such as competition, predation, herbivory, disease, and mutualisms, may also be just as if not more important,” Feeley explains.

“The more realistic you make the models, and the more variables you consider, the number of future options available to species almost invariably decreases.” Even if species are capable of keeping pace with climate change and move upslope, they will still suffer a reduction in available habitat as land area decreases the further up the mountain they go.

“For example, in Costa Rica there is over 6.5 times as much land area between 1800 m and the highest plot at 2800 m as between 2800 m and the highest point in Costa Rica at 3820 m elevation,” the scientists write. Species already adapted to cooler high elevation temperatures will have nowhere to migrate into. And other problems also face tropical species that are a long way from a mountain to begin with.

“Within the tropics there is no latitudinal gradient in temperature. This is very important because it means that species cannot migrate towards higher latitudes to escape the heat but instead must migrate to higher elevations where it does get invariably cooler,” Feeley explains. “For lowland species in the middle of the Amazon basin where it is remarkably flat, this means that they will have to migrate huge, perhaps impossibly huge, distances before they experience any sort of relief.” Add to that the destruction of habitat, and movement becomes more challenging still.

“If species cannot migrate upslope, then their potential responses to climate change are greatly limited. Indeed, the only options left are to adapt or to acclimate. And given the speed at which the world is now changing, I think it is safe to say that adaptation is not a viable option, at least for large long-lived trees with long generation times. So the question becomes, can lowland trees acclimate to climate change?” Feeley posits. “The future of global diversity depends on the answer to this question but right now we are nowhere close to having that answer.”

Species in the lowland tropics inhabit one of the hottest regions on earth, so it is impossible to gauge their heat preferences above present-day temperatures by looking at their range distributions. However, understanding the upper limit of species’ heat tolerance would vastly improve predictions about species survival in a warming world.

Map showing the team's study plots (green squares) stretching from the lowlands up the mountain to a height of 2800 metres. Image credit Kenneth Feeley.

Map showing the team’s study plots (green squares) stretching from the lowlands up the mountain to a height of 2800 metres. Image credit Kenneth Feeley.

“By far the single most important factor is how much warming the species can tolerate. If they can tolerate a significant amount of warming, then our predictions are relatively sanguine. If species are intolerant of warming, then their future will be dependent on migrations and predictions for the tropics become very bleak,” explains Feeley.

To date, the majority of studies examining the potential impact of climate change have focused on North America and Europe.

“In general, there is a dearth of studies looking at the impacts of climate change on the distributions of tropical species. This is despite the fact that the vast majority of species are tropical,” Feeley told mongabay.com. “We desperately need to fill the void and have more studies from the tropics. To do these studies we need a better and more systematic system of ecosystem monitoring plots and more importantly, but also harder, a better understanding of the complex abiotic (non-biological) and biotic (biological) factors that regulate species distributions and dynamics.”

Feeley and colleagues continue to monitor their study plots in Costa Rica and Peru, and are expanding their research to better understand the processes that determine species range distributions and movements.

“We are in the initial phase of a large-scale transplant study in which we are moving thousands of seedlings of dozens of tree species up and down the slopes of the Andes under various experimental treatments in order to identify the specific biotic and abiotic factors that limit their distributions,” he says. “Once we have this information we can build it into improved predictions for the fate of these species on a warmer planet.”

The best hope for conserving forests in the face of climate change, and climate-driven migrations, is to anticipate species movements, says Feeley.

“We need to expand the time scale of our thinking and determine not just where species are today but where they will be a hundred years from now. And then we need to protect both of those places and everything in between.”

Paper: Feeley K.J., Hurtado J., Saatchi S., Silman M.R., and Clark D.B. 2013. Compositional shifts in Costa Rican forests due to climate-driven species migrations. Global Change Biology, Available Online. DOI: 10.1111/gcb.12300