Another fire season is underway in the hot, dry western U.S. Wildfires are wreaking havoc in New Mexico and Colorado, where more than 32,000 people have been evacuated. And who knows where other fires will break out before summer ends.

This is exactly the kind of intense wildfire season we can expect as the climate changes thanks to our continuing emissions of greenhouse gases. Global warming is anticipated to make wet regions wetter and dry regions drier.

To some extent that is already happening; a dry winter set the stage for an early fire season. Worse, warmer winters have allowed pests like the mountain pine beetle to thrive. The insect has munched its way through mountain forests from British Columbia down through Colorado, leaving plenty of dead timber to fuel fires, also a consequence of the fire suppression policies of past decades.

Ultimately, global warming may eliminate the iconic ponderosa pine forests. Blazing fires could burn down existing stands, opening room for colonization by faster-growing prairie grasses or other plants. And a changing climate may prove more amenable to grassland than forest.

But we may gain forests in other parts of the world. That might happen to Africa's savannahs, where the species causing these transitions first evolved.

—David Biello

[The above text is a transcript of this podcast.]