Gaps left in the tree canopy increase the lizard population

By Environmental News Network staff

(ENN) -- When people living in remote sectors of the Amazon rain forest harvest a single tree and cut it into boards on site, certain lizard populations grow and become more voracious, according to a University of Oklahoma researcher.

"Single-tree harvesting is widespread. People live in remote areas and when they need boards, they enter the forest, find the tree they need, and cut it up," said Laurie Vitt, who published research on the lizards in the June issue of Conservation Biology.

Single-tree harvesting creates gaps in the canopy that are more open than those left by natural tree falls. These man-made gaps are also warmer than natural gaps and cause an increase in the population of heliothermic lizards -- those lizards that require high body temperatures to be active and get their heat from the sun.

The problem with having more heliothermic lizards is that after warming themselves in forest gaps, they go into the forest to forage, often seeking out hidden prey. Because they are among the largest lizards in the forest -- some can be more than three feet long -- an increase in heliotherms could lead to the reduction or elimination of smaller terrestrial vertebrates, including other lizards and frogs.

Among the largest lizards in the forest, the golden tegu can be more than three feet long

Heliothermic lizards are "terrestrial, eat anything that moves within the right size range, have relatively high body temperatures (as lizards go), and are very active when foraging," said Vitt.

Although an increase in the distance between harvested trees might keep the lizards from traveling between the gaps and thus keep the balance of forest species in check, Vitt said that is unlikely to happen.

"The question about increasing distance from cut tree to cut tree seems irrelevant to me," he said. "You have to keep in mind that we are talking about a process that occurs because people live in remote areas, have no easy access to supplies and have no source of income. Consequently, convincing them to do anything differently is a non-concept."

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