Guatemala may repeat Mayan history

ENS, Monday 15 June 1998

The Peten region of Guatemala had one of the densest human populations of any time in human history during Mayan times. If deforestation had anything to do with the collapse of Mayan civilization, and there are scientists who believe this, history could be about to repeat itself.

The Maya inexplicably disappeared about 500 years prior to Christopher Columbus' arrival in the West Indies. As scientists try to determine why, their discoveries paint a bleak picture for the near future.

At the time of their collapse, it appears there were no trees and that a major drought ensued, said Dr. Thomas Sever, an archaeologist with NASA's Marshall Space Flight Center. We're not sure whether these are the result of local or global changes. But we do know that although most of the land is not suitable for farming by today's standards, the Mayan civilization supported one of the greatest population densities ever.

As Guatemala's population booms in a time of relative peace, the government of Guatemala is concerned that history may repeat itself. Many Guatemalans systematically burn down the rain forest to make way for farmland that lasts only three years.

Realizing that the forests were targeted for major development, the government of Guatemala in the 1980s asked NASA to use its Landsat satellites and other tools to map the rain forests in the Peten region so Guatemala's leaders would know what was left that could be preserved.

We were startled by what we saw, Sever said. You often cannot see borders from space because those are just lines on paper. Landsat showed us rain forest up to a line, then tilled land. That was where Guatemala stopped and Mexico began.

The images led President Vinicio Cerezo of Guatemala to ask that nation's congress to set the area aside as the Maya Biosphere Reserve in 1990.

NASA and the Central American Commission on Environment and Development agreed to a joint research effort in the area. The results of work by Sever and several colleagues are in Pixels and People, a book published recently by the National Academy Press in Washington.

The Peten covers 12,960 square miles -- a third of Guatemala. Its population includes more than 800 species of trees, 500 species of birds, and large populations of mammals, including monkeys, jaguars, tapirs and -- in rising numbers -- humans.

At first glance, the undeveloped areas of the Peten look untouched, said Sever. It's actually a regenerated rain forest, one that had recovered from human abuse a millennia ago. The tragedy is that now the story is about to repeat itself. The lessons from this activity can portend what may happen to other developing nations that are destroying forests for short-term economic gain.

From 250 to 900 C.E. was the Classic Mayan period which saw the building of many cities centered on temples and ball courts and connected by extensive road systems. The Peten region had one of the densest human populations of any time in human history: almost 2,600 people per square mile in the cities, and from 20 to 50 percent as many in the rural areas.

Then they just disappeared, in the space of 100 years, perhaps as fast as 20 years, Sever said. From 830 to 930, the population plummeted by two-thirds, and continued to decline for centuries afterwards. It nearly reached zero in the 1800s.

It may be one of the greatest demographic disasters in human experience.

We do not understand how they could feed themselves, Sever said. We think that the bajos -- covering about 40 percent of the land -- are the reason.

Bajos are seasonally flooded swamps that readily show up on satellite images.

The natives told Sever and his team that what satellite imagery perceived as three types of bajos were actually seven types. Of those, two or three are moist enough during the dry season to support agriculture, thus adding to the land that the ancient Maya could till.

Still, the researchers asked, if bajo agriculture worked well, why did Mayan civilization collapse after the population had declined somewhat and thus placed less demand on the land?

The collapse took a terrible toll on this society, Sever said. We see evidence of houses and temples falling into disrepair, of a people living in something like you would see in a post-apocalypse movie.

So what happened?

The disappearance of trees may be a clue. A climatic change that dropped the water table would also dry up bajos used for agriculture. In turn, that would force the Mayans to carve out farmland from the jungle.

Despite its broad diversity of life, the rain forest is life on the edge. It does not have deep soil in which life can root itself. Instead, the survival of the rain forest depends on a frenetic recycling of everything.

Land that is converted from jungle to farm will have a 100 percent crop yield the first year, 40 percent the next year, and even less the third, Sever said. So, the farmers move on and convert more jungle to farmland. But the wasted land does not recover for hundreds of years. Eventually, the farmers will destroy their way of life.

For now, though, deforestation rather than adaptation is the rule for the descendants of the ancient Mayans. Since 1960, the population has grown from 26,000 to more than 300,000. In January 1997, as part of a peace settlement between the government and rebels, parts of the Maya Biosphere Reserve were opened for farming.

Development in the preserve ranges from slash-and-burn agriculture to selective logging of mahogany, capturing endangered animals for sale abroad, archaeological looting and marijuana production.

We used Landsat images to measure the 'greenness' of the Peten, Sever said. Basically we subtract one image of vegetation from an older image of vegetation. The result is an alarming picture of where trees are gone.

One thing they have discovered is that 90 percent of deforestation happens within 1.2 miles of a road. An illegal pipeline -- discovered in a Landsat image -- has provided a new route through the heart of the jungle.

It's like watching blood vessels grow so a tumor can move forward and consume tissue, Sever said. The rates of deforestation are not constant across the Peten. We can see areas where it is almost absent, like Carmelita in the central Peten where traditional farming is practiced, and Tikal, where guards are on duty.

One of the really troubling aspects is that we can also see islands of forests left when people settle an area or when a pipeline is built. We're not sure how this affects the animals and their feeding and mating territories, or how it might isolate and strangle their genetic diversity.

Satellite imagery makes this work easier in more ways than just providing quick pictures of the study area. They help Sever and his colleagues give the local citizens a new view of their homeland and a better sense of ownership.

We always take lots of copies of the Landsat images and leave at least one with each village we visit, Sever said. This takes away some of the mystery and fear because we share what we know and make the local leaders a part of our work. In time, word spreads and people become more willing to support us and help interpret local features that we can't quite make out in the pictures.

Sever's studies of the Peten area continue with new urgency caused by fires burning large areas of rain forest in the wake of El Ni o extending the dry season. This raises the question of whether El Ni o events a thousand years ago may have played a role in destroying the Mayan peoples.

How much damage is being done by now will not be known until the fires end and the smoke clears so satellites can see the area again.

We don't know yet because we don't know that much about the history of El Ni o, Sever said. We have some evidence in Peru that the Incas went through extended periods of drought that may have been influenced by El Ni o. Because the rain forest recycles everything very quickly, it will be hard to find clues like tree rings in old-growth forests. But what is happening to Central America now could certainly be a good model of what happened to the ancient Maya. History seems to be repeating itself. We have to convince enough people of the lessons before it's too late.