Rising Mountains & Spiking Temperatures Spurred Amazon's Biodiversity

By Andrew Moseman | November 12, 2010 10:34 am

AmazonRforestWhat does it take to make a wellspring of biodiversity like the Amazon rainforest? A huge mountain range, a blast of heat, and a little time.

A pair of studies in this week’s edition of Science attempt to sort through tropical natural history and reach the root causes of Amazonia’s embarrassment of biological riches. The first, led by palaeoecologist Carina Hoorn, points to the influence of the Andes Mountains, the spine of South America that runs up its western coast. Sometime between about 35 and 65 million years ago, colliding tectonic plates sent the Andes bulging up. According to the researchers, the birth of a mountain range set of an ecological chain reaction.

The rising mountains that resulted from the uplift blocked humid air from the Atlantic, eventually increasing rainfall along the eastern flank of what became the Andes that eroded nutrient-loaded soils off the mountains. The Andes also kept water from draining into the Pacific, helping form vast wetlands about 23 million years ago that were home to a wide range of mollusks and reptiles. [LiveScience]

About 7 million years ago those wetlands dried up. But they left behind a swath of fertile soil, the scientists say, perfect for a rainforest to colonize. A little later, about 3.5 million years ago, the Panama isthmus emerged, and that sliver of land provided a bridge for even more species to reach the Amazon.

And then there’s the heat. A little than 56 million years ago—during the window when the Andes commenced their ascent—a blast of sudden warming struck the Earth. The event is called the Palaeocene-Eocene Thermal Maximum (PETM), during which the temperature shot up by as much as 5 degrees Celsius (9 degrees Fahrenheit) and the global thermostat stayed there for about 200,000 years. One might think that a temperature shock would suppress biodiversity, but that is not what the scientists found in the fossil record when they surveyed in Colombia and Venezuela.

“We were expecting to find rapid extinction, a total change in the forest,” says study leader Carlos Jaramillo, a biologist at the Smithsonian Tropical Research Institute in Balboa, Panama. “What we found was just the opposite — a very fast addition of many new species, and a huge spike in the diversity of tropical plants.” [Science News]

Indeed, this warm period invited some of the Amazon‘s signature species, Jaramillo says.

The pollen fossil record shows that some important plant families, such as Myrtaceae, which includes eucalyptus, and Passifloraceae–the passion flowers–made their first appearance during the thermal maximum. The tropics have remained the most species-diverse area of the world ever since. [Scientific American]

On the surface, this burst of biodiversity during a warm spike might suggest plants actually could thrive if the planet suddenly heats up. But Jaramillo—admittedly wary that his study of the Earth 56 million years ago will be used as ammunition to argue that modern climate change doesn’t matter—warns that this connection is far from clear. First, 200,000 years is hasty on the geological time scale, but global warming is happening at a much faster pace. Furthermore, he says, Earth was wetter during the PETM that it’s likely to be in the near future, and deforestation has rendered the rainforest thinner today that it probably was then.

Related Content:
DISCOVER: Black Gold of the Amazon
DISCOVER: On the Origin on (Amazonian) Species
80beats: Amazonians Turned Poor Land Into Great Farms—and Healthy Ecosystems
80beats: Chopping Down the Amazon Causes a Short-Term Boom, Long-Term Bust
80beats: Amazonian Mega-Storm Knocked Down Half a Billion Trees

Image: Wikimedia Commons

CATEGORIZED UNDER: Environment, Living World
  • cray

    “One might think that a temperature shock would suppress biodiversity”–Liberals/Socialists NEVER let up. Ideology ALWAYS trumps facts, evidence, reason, and common sense. These members of the so-called “reality based community” believe anything Karl Marx and Barack Obama say is by definition “reality”.

  • http://blogs.discovermagazine.com/80beats/ Eliza Strickland

    @ cray:

    Karl Marx and Barack Obama have nothing to do with this post. Dramatic changes to the climate, such as ice ages and rapid warming events, typically cause drastic changes to life on Earth. Please keep comments on-topic.

    — Eliza, DISCOVER online news editor

  • VIP

    Please keep this information from David Susuki and Al Gore, they will have to revise the invention of the automobile back a few million years.

  • Dante The Canadian

    Interesting that BOTH sides of the Global Warming equation are concerned about this information. On the one hand, opponents of the Global Warming Model will use this information to say once again that Global Warming is a natural phenomenon and not a Man made Cataclysm. On the other hand, proponents of Global Warming will no doubt say that the speed of warming now is much faster, as pointed out in the article, than it was 56 million years ago.

    Must there always be a right and wrong here? Could it not be that the earth is warming in part due to natural phenomenon but that human activity is certainly affecting the speed of the warm up???? What bugs me more than anything about this and other debates is the polarization of a very grey argument. Here we have clear evidence, once again, that the earth goes through rapid changes in climate but the Global Warming faction will disrepute the findings. On the other hand, here we also have evidence showing ‘rapid’ climate change occurs over 200, 000 odd years but the Global Warming deniers will try to hide that fact for their own purpose.

    Why can we, as humans, not do something because it’s the right thing to do, regardless of whether or not it will save the planet from dying???? We know that by polluting less, burning less fossil fuels, being more environmentally consious and friendly will make our lives and the lives of the creatures and organisms we share this planet with much better. Our lakes, rivers, and oceans will be cleaner, our health will improve, our air will be easier and cleaner to breathe, our food will taste better, and thus our standard of living will be higher!!!

    Instead, we bicker and argue and debate and fight and point fingers and reject and refuse and repell and deny losing focus on what is most important, our daily quality of life. Too often humanity gets caught up in huge philosophical and socio-economic debates over issues that, when cut down to the core, can be solved very easily IF there is a WILL to solve them. The problem is, humanity doesn’t seem to have that will.

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