What role does poison ivy play in its natural ecosystem?

Poison ivy provides a food source for many species of birds, as well as larger mammals such as white-tailed deer. Smaller animals use it as shelter. Some animals might even prefer poison ivy so much that they would eat it rather than your garden plants.

It commonly grows on the edges of forests, streams, and roads, or in disturbed areas. The edges of forests are commonly vibrant with several species of briars which serve to create a protective layer to shield the inner forest from harsh weather conditions, as well as providing a layer of shelter for smaller animals. A teacher once explained this to me as a sort of skin for the forest. I suspect that poison ivy provides a similar service, as it is often found among briars and the edges of forests.

The Cherokee revered poison ivy and other "warrior plants" for their ability to quickly respond to disturbances in the forest. When an area is disturbed, say from a storm knocking down trees, or human development, plants like poison ivy and some briars like blackberry or smilax, are some of the first plants to become established in that area. These plants have strong roots and help to limit erosion and condition the soil to prepare it for more forest to grow there in the future.

Poison ivy is not very shade resistant, it needs lots of sun. So it can sometimes be found in the understory of a forest, but most likely if it is then that forest is relatively young. In a mature forest (100+ years) it is unlikely to find poison ivy crawling on the ground, although it still may climb up the sides of some trees.

Ironically, the level of CO2 in the air affects the growth rate and the level of dermatitis causing oil in poison ivy, so with the rising levels of CO2 caused by human activity in our air, the more obnoxious poison ivy becomes.

Also ironically, the more development that occurs, hence the more we disturb ecosystems, the more prolific the population of poison ivy will become.

It seems as if it is seriously trying to combat our growth as we know it.

The Cherokees may have been more right than they knew, or maybe they did know.