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Wednesday, July 30, 2008

NATURAL SELECTIONS

Climate change in Costa Rica


A couple of weeks ago I was woken at dawn by the booming screeches of the aptly named Howler Monkey. I was in Costa Rica, in the cloud forest of Monteverde.

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The author deep in the Monteverde cloud forest of Costa Rica, which gets a whopping 3,000 mm of rain a year.

Among those who know, Monteverde is famous because the cloud-forest reserve is at the center of a crossroads — to the north is temperate America, to the south the Tropics. Animals and plants meet in the isthmus connecting the north and south — and there they mingle.

To the west is the Pacific Ocean; to the east the Atlantic. On top of all that, the country is divided by a volcanic mountain chain — to the east of which lies the Caribbean tectonic plate, to the west the Pacific plate.

It is this unique location and biogeography that gives Monteverde — and indeed the country — its remarkable and unparalleled biodiversity. For anyone with even a passing interest in wildlife, the place is an embarrassment of biological riches.

There are more varieties of butterflies and moths in Costa Rica, for example, than in all of Africa — hardly a continent lacking in jungles or diverse habitats. As well, almost 900 species of birds have been recorded in this small country — more than in the United States and Canada combined.

In total there are more than 500,000 known species in Costa Rica — that's 5 percent of all the species in the world living on just 50,000 sq. km of land — a place about the size of West Virginia.

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Costa Rica, though only the size of West Virginia, is home to more than 500,000 known animal species, inlcuding more varieties of moths and butterflies, such as this Clearwing Butterfly, than in the whole of Africa ROWAN HOOPER PHOTOS

When I visited it was the rainy season, and not long after waking to the Howler Monkeys my friend and I, and a guide, Ricardo, hiked into the forest wearing rubber boots and carrying waterproof jackets and jungle hats.

After all, Monteverde gets a whopping 3,000 mm of rain a year, and even when it doesn't rain I'd heard that the clouds and mist carry so much moisture that you'd likely be soaked without protective gear.

Not this time. The sun blazed all day. And the next day too, when we hiked for 7 hours in the forest. Well, aren't we lucky, we said to each other a little ruefully, here we are in the cloud forest and there are no clouds.

We'd seen clouds the day before, driving up the precipitous mountain roads as clouds swept up from the Pacific and over the forest. And from my hotel room, right on the edge of the forest reserve, I saw the mist pushing through the trees. But when we walked through the forest — no clouds.

When I got back from Central America I found some research on a new regional climate model, made specifically to look in detail at Costa Rica.

To predict the effects of climate change, Ambarish Karmalkar of the University of Massachusetts' Amherst Climate System Research Center used a regional modeling system capable of accommodating the complex topography of Costa Rica.

He tested the computer model using actual rainfall and temperature data collected in Central America between 1961 and 1990, then looked at what would happen if carbon dioxide in the atmosphere doubled.

The simulation predicts that temperature will rise by 3 C, and that the mountainous Pacific slopes and the Caribbean lowlands will receive up to 30 percent less rain. There will be an overall increase in the height of the cloud base of up to 300 meters.

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"We have completed a regional climate model showing that many areas of Costa Rica will become warmer and drier as climate change accelerates, and these changes will be amplified at higher elevations," said Karmalkar.

As this happens, plants and animals will try to migrate up slope, to conditions where they can more comfortably grow, forage and reproduce. But other species already live in these regions, and eventually they will reach the top of the mountains.

"Central America is a major, emerging 'hot spot' in the Tropics where climate- change impacts on the environment will be pronounced, and the loss of species associated with climate has already been identified," Karmalkar notes.

I should know better, but it is hard not to equate the predictions Karmalkar's model makes — that mountainous forests in Costa Rica will become warmer and drier as climate change accelerates — with my experience in the cloud forest.

Now, it makes no scientific sense to link single events to global-climate change. So it is not possible to say, for example, that Hurricane Katrina, the storm that so devastated New Orleans in August 2005, was caused by global warming. It was this implicit link, among others, that got Al Gore into trouble with his film "An Inconvenient Truth."

It was obviously just chance — or our bad luck, which was how we saw it — that there were no clouds when we were in the cloud forest. But neither were there any frogs — none I could see or hear, anyway.

"You don't see frogs," said Ricardo, who has worked in the cloud forest for 10 years. "You used to see more, but not now."

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You used also to see, if you were lucky, the Golden Toad of Monteverde. If the Polar Bear has become a symbol of global warming in the Arctic, the Golden Toad has that dubious honor in Costa Rica. The spectacular bright-yellow-orange amphibian is classified as extinct — not having been seen since 1989.

Its demise has also been blamed on global warming. If so, it will likely be only one of many such extinctions. You can argue the point all you like about the causes of climate change, but the fact is that an overwhelming majority of scientists — and now even politicians — agree that it is mostly driven by human activity.

So although it is difficult to pin to global-warming individual examples such as Hurricane Katrina or the demise of the Golden Toad, it is fair to say that Costa Rica — one of the most biodiverse countries on Earth — will lose species as the planet warms up.

The second volume of Natural Selections columns translated into Japanese is published by Shinchosha. The title is "Hito wa ima mo shinka shiteru (The Evolving Human: How new biology explains your journey through life)." It is priced at ¥1,500.


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