Could Birds and Bats Help Rebuild Forests?

Scientists have come up with a bit of trickery in their effort to restore parts of tropical forests that were "slashed and burned" to make way for agriculture, and later abandoned.

They have embarked on a multi-year international project to see if they can get birds and bats to literally do their spade work.

It's largely the brainchild of Henry Howe, a renowned expert on reforestation and a professor of biological sciences at the University of Illinois at Chicago.

The basic plan is to plant fast-growing trees, like figs, that produce fruit that will attract birds and bats into the slashed area, where they will "upchuck or defecate" seeds from nearby forests, thus returning species that once made the area rich in plant and animal biodiversity.

"I think they'll do the work for us," says Howe.

Howe is leader of an international team, funded initially by the U.S. National Science Foundation, that has leased 16 land parcels in Mexico's Gulf Coast state of Veracruz to see if coaxing birds and bats back into the area will help restore the forest to its former glory.

From Forest to Farmland to …

Huge areas in tropical forests around the world have been stripped of their natural vegetation and converted to agriculture, thus destroying areas that are vital habitats for a wide range of plants and animals. The result has been a devastating decline in diversity, as well as a huge reduction in biological material that can absorb carbon dioxide – a greenhouse gas – from the atmosphere.

But Howe says that in many cases, land that was suitable for a forest turns out to be lousy for agriculture.

He says if you fly over some areas, "you can see rocks peeking through very thin soil."

"A lot of tropical soil isn't suitable for agriculture" because it lacks the nutrients and the depth needed to produce crops, he adds.

The result is a patchwork quilt of farmland and abandoned plots where a forest once stood. About 90 percent of the seeds that provide new plants in a rainforest are dispersed by birds, bats and insects, Howe says. Only about 10 percent are carried by the wind.

Hostile Habitat

But when the forest is chopped up, animals no longer go into the areas that are abandoned by frustrated farmers because there isn't anything there for them to eat. Only seeds that are carried by the wind arrive there, thus dramatically reducing the variety of trees and plants, and providing little incentive for animals to return.

So Howe teamed up with several colleagues, including a former student, Christina Martinez-Garza, now a biologist at the Autonomous University of Morelos in Mexico; Martin Ricker, director of a biological station in Veracruz; and Rodolfo Dirzo, professor of biological science at Stanford University. Their goal is to test the hypothesis that birds and bats can be lured back into an area to aide in reforestation.

The answer may seem obvious, but some researchers believe it may not work. Once a tropical forest is cut down, the growing conditions become very different.

"It is a lot hotter and a lot drier out in the open (once the trees are gone) than it is in the rain forest interior," Howe says.

But he is reasonably convinced the land could be reclaimed if he can get over one hurdle.

The seeds needed to do the job "just don't get there," he says.

Rapid Restoration

The researchers will begin with 12 species of trees that are normally dispersed by animals, and that produce the fruit they need to survive. Some of these are very fast-growing trees, and they don't live for many years.

"They germinate quickly, grow quickly, and die quickly, maybe 20 years at most," Howe says. "A fig tree can grow 40 feet tall in four years."

So if the plan works, within four or five years the researchers should see trees that produce fruit, and a return to the area of animals that distribute even more seeds. Hopefully, that will lead to a robust, diverse forest.

Of course, much of the land will remain in farming, so the forest won't be as grand as it once was. But parts of it, now barren and abandoned, will once again be a viable habitat for many creatures.

And all because some creative scientists teamed up with birds and bats to do what comes naturally.

Lee Dye's column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.