As the world burns.

• Author: Larsen, Janet
• Position: Wildfires - EYE ON ECOLOGY

FUTURE FIREFIGHTERS have their work cut out for them. Perhaps nowhere does this hit home harder than in Australia, where, in early 2009, a persistent drought, high winds, and scorching temperatures set the stage for the worst wildfire in the country's history. On Feb. 9, now known as "Black Saturday," the mercury in Melbourne topped 115[degrees]F as fires burned more than 1,000,000 acres in the state of Victoria--destroying over 2,000 homes and killing more than 170 people, tens of thousands of cattle and sheep, and 1,000,000 native animals.

Even as more people move into fire-prone wildlands around the world, the intense droughts and higher temperatures that come with global warming are likely to make fires more frequent and severe in many areas. For southeastern Australia, home to much of the country's population, climate change could triple the number of extreme fire risk days by 2050.

Although fires typically make the news only when they grow large and put fives or property at risk, on any given day thousands of wildfires bum worldwide. Fire is a natural and important process in many ecosystems, clearing the land and recycling organic matter into the soil. Some 40% of the Earth's land is covered with fire-prone vegetation. A number of plants--such as giant Sequoia trees and certain prairie grasses--need fire to propagate by creating the right conditions for them to flourish.

Fire patterns have changed over time as human populations have grown and altered landscapes by clearing forests, allowing pasture animals to overgraze grasslands, and importing new plant species. Across parts of the western U.S., for instance, cheatgrass, an invasive annual adapted to frequent bums, has supplanted native brash, desert shrub, and perennial grasses that typically experience longer intervals between rims. In other areas, mixed-age and -species forests have been replaced by single-species plantations where flames can jump easily from tree to tree. The result, instead of a low-intensity restorative fire, is a flame so hot that it can cause lasting harm to soil.

Humans also have altered fire patterns through deliberate suppression. After 1910, when a severe wildfire charred more than 3,000,000 acres of American forest in just two days, the strong desire to protect timber resources gave life to a policy of extinguishing fires quickly. For decades, firefighters proved remarkably successful in this endeavor, but the upshot was that forests became so loaded...