In 1995 and 1997, NASA sent me to Brazil to measure the atmosphere during the tropical burning season. One day the smoke was so thick at a remote camp on the Cristalino River that no ultraviolet sunlight could be measured on the forest floor. Something else was missing, because no birds could be heard or seen.

All that changed back at the river's edge. There was still plenty of smoke, but birds were singing, and iridescent butterflies were everywhere. Three bird watchers at the camp were having a great time adding new species to their notebooks.

The sharp increase in the abundance of animal life along the river was an example of what ecologists call the edge effect. Before that experience in Brazil I had noticed the edge effect while riding a bicycle from Albuquerque, N.M., to the Padre Island National Seashore.

We saw only antelopes in New Mexico and coyotes in West Texas. But there was an obvious increase in animal activity in the Hill Country where the road crossed rivers and streams and sliced through the borders between fields and woods.

The fence line between our place and a neighbor's open field is often populated by more birds, dragonflies and butterflies than the adjacent woods. Feral hogs that visit our place do much more damage along boundaries between wooded and open areas.

Our house is under trees adjacent to an open field to the north. On most days there are many more birds around the house than in the woods.

The edge effect shows that many animals can quickly adapt to changes in environmental destruction caused by human activity and fires. Plants also are influenced by the edge effect. There can be at least as many species of plants along fence lines as in adjacent fields or wooded areas.

Edge effects are not always beneficial. For example, herbicides applied to agricultural fields can cause great damage to plants along adjacent boundaries.

Large animals often travel along boundaries and trails made by people. But the range they need to forage or hunt is reduced when development arrives, even though there may be more edge effects.

A survey of edge-effect plants and animals might make a good science fair project. Students can observe edge effects by walking through and around city parks and even in some neighborhoods. If safe roads are available, a bike ride provides an excellent way to observe edge effects in rural areas.

From inside a car you'll not hear singing warblers, gobbling turkeys, rustling armadillos or the sound of pecans falling into leaves.

But you surely will when walking or cycling.
