How Might Climate Change Affect Asian Elephants?

elephantsThis morning’s news brought word of a study in Nature Climate Change that predicts devastating global species losses as a result of climate change. The analysis found that some 57 percent of plants and 34 percent of animals would lose more than half of their range by the 2080s if nothing is done to stem the tide of rising greenhouse gases.

“This broader issue of potential range loss in widespread species is a serious concern as even small declines in these species can significantly disrupt ecosystems,” the study’s lead author, Rachel Warren of the University of East Anglia in England, said in a statement.

But it might be easy for many people to ignore something as nebulous as “plants” or “animals” or “ecosystems.” After all, maybe your favorite one won’t be affected. So lets look at another recent study, one of Asian elephants in Myanmar (Burma) that was just published online in Ecology.

Researchers from the United Kingdom and Germany analyzed longevity data from 1,024 semi-captive elephants that were born between 1948 and 1999. These elephants are used in places like the timber industry in Myanmar. They work during the day but forage for food on their own at night, and they breed at will. They have many similarities to fully wild elephants but are easier to study.

This dataset included not just information on how long each elephant lived and how they died, but also about the environmental conditions during their lifespans — specifically, temperatures and rainfall. That let the scientists see how the elephants survived during hot versus cold spells, or during rainy seasons and droughts.

Both temperature and rainfall influenced the survival of elephants over the time of the study. Heat was especially bad — most deaths occurred when temperatures were above 24 degrees Celsius (75 degrees Fahrenheit). Very cold times also weren’t good for the elephants, nor was drought.

That is not good news for Asian elephants, which are already dwindling in numbers. Southeast Asia is expected to warm by up to 3 degrees C over the next 30 to 40 years, accompanied by changes to the yearly monsoon season. “Increased extremes in temperature and rainfall (both within a year and between years) may therefore lead to significant increases in mortality of Myanmar elephants in the near future,” the researchers write.

There has been some debate in the scientific community about whether long-lived creatures will be affected all that much by climate change, and whether species in tropical regions, already adapted for heat, will do as badly under warming conditions. This study, of long-lived elephants living in tropical Myanmar, puts holes in both those theories. “Despite living in a highly seasonal environment, our results indicate that modest deviations from optimal conditions have effects on Asian elephant survival,” the researchers write. Elephant survival under even modest climate changes, therefore, will be a challenge.

Image of elephants in Myanmar courtesy of flickr user Mandala Travel

If You Like To Eat King Or Snow Crab, Worry About Climate Change

red_king_crabIf you eat crab, there’s a decent chance you’ve had king crab or snow crab — the type they often sell in grocery stores and restaurants as just big red arms — which are brought up from chilly waters in places like the Bering Sea off Alaska. The future for these species is uncertain; as with many tasty critters, they’re overfished and on the decline. But more worryingly, finds a study in PLOS One, the crabs are vulnerable to climate change.

Researchers from the National Marine Fisheries Service Kodiak Laboratory in Alaska studied two species of crab: the red king crab (the most sought-after kind of king crab) and a snow crab known as the Tanner crab. They raised young crabs for a little over half a year in tanks with sea water at one of three pH levels — 8.0, 7.8, and 7.5 — and then tracked the crabs’ growth.

The scientists were interested in the effects of ocean acidification on the crabs. As we pump more and more carbon dioxide into the atmosphere, the ocean absorbs some of that gas, which causes the water to become more acidic over time. Some areas of the world will be affected more than others, and northern regions are expected to become more acidic than tropical ones. The three different pH levels range from the current state of the water (8.0) to what will exist at the end of the century (7.8) to what could exist in the not-too-distant future (7.5).

Ocean acidification is a particular worry for organisms that rely on calcium carbonate to construct their skeleton or shell, like coral and crabs. If the pH of the water is too acidic, it will be too difficult, too costly for these organisms to turn calcium and carbonate into calcium carbonate to build their bodies.

At the 8.0 pH level, the crabs grew just fine. Some crabs died, but that’s normal. At a pH of 7.8, more crabs died; less than 40 percent of the red king crabs and about half of the Tanner crabs survived to the end of the study period. And at the 7.5 pH level, less than 40 percent of the Tanner crabs lived to the end, and all of the red king crabs died within 95 days. Growth rates were also affected by the acidic waters, with the crabs not growing as well when pH was low.

Given these results, the researchers predict that ocean acidification will cause a serious decline in these species by the end of the century, with red king crabs affected first. Even before then, though, small increases in acidity could affect crab growth. Because smaller crabs are more vulnerable to predators, they’re more likely to get eaten and not survive too long. Their smaller size could affect the predators that eat them (they won’t be as satiated by their crab meals), and that’s just the beginning of a host of changes that could sweep through the food web, affecting species that may not be directly impacted by water pH.

Crabs and other species may be able to adapt to more acidic waters. There are some cousins to the red king and Tanner crabs that live in deep places with lower pH, which shows that such adaptation is possible. But greater acidity at the surface could also open up these waters to the deep-sea species, resulting in a crab competition. What this means for the species we love to eat, well, only time will tell.

Image of red king crab courtesy of The Children’s Museum of Indianapolis, via wikimedia commons