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Last Updated: Wednesday, 31 October 2007, 11:12 GMT
California's natural born killers
Californian wildfire (Image: AP)

By Mark Kinver
Science and nature reporter, BBC News

Earth, wind and fire formed a deadly trilogy in California this month to reduce an estimated 1,800 sq km (700 sq miles) to ash and charred remains in a matter of days.

The US state's worst drought for 130 years and the arrival of exceptionally strong seasonal winds fuelled the devastating wildfires that claimed at least 14 lives, destroyed thousands of homes and triggered the biggest mass evacuation in the US state's history.

As people returned to their neighbourhoods and slowly came to terms with their losses, ecologists began the task of assessing the impact to the region's environment.

Satellite images were able to record the full extent of the fires

"We have to get out into the field to assess the extent of the fires," said Trish Smith, a senior ecologist for The Nature Conservancy.

From her office in southern California, she told BBC News that one of the first jobs would be to see if there were any areas that had escaped from being engulfed by flames.

"It is the lack of refuge that really is of most concern," Ms Smith revealed.

"Many of these fires were extremely large and we are worried about the availability of refuges for wildlife to take cover, and from which to recolonise the affected areas."

Recovery time

Although the region's ecology has evolved alongside wildfires for millennia, she said it was the frequency of these blazes that was raising concern.

A scorched ornament of a deer (Getty Images)
There is not much we can do to change the fire ecology because our natural systems here have evolved with fire
Trish Smith, The Nature Conservancy

Southern California also suffered devastating wildfires in 2003, which destroyed more than 3,000 sq km (1,160 sq miles) of habitat.

"The frequency is a huge issue that will affect whether an area fully recovers," Ms Smith explained.

"Frequent fires really increase the potential for invasive species, and they make it difficult for the natural scrub and chaparral plant communities to recover."

She added that conservation groups were concerned for a number of species.

"One example is the tecate cypress, an endemic tree species that is adapted to fire, and actually needs fire every 40 to 70 years to open up its cones and release its seeds.

"But if the trees burn too frequently - say more than once every 20 years - then the trees are not mature enough to produce cones and you face losing them."

Ms Smith added that a bird called the cactus wren was another potential casualty of the fires.

"It is correlated with stands of large, mature cactus. If the cactus burns too frequently then the wren is also lost because it only nests in mature cactus."

Parched land

Even before the wildfires began, animals and plants were feeling the strain of being caught in the state's worst drought for 130 years.

Map: California fires

The US Drought Monitor, made up of federal agencies and academic groups, currently lists southern California as experiencing an extreme drought.

It also says that almost 95% of the state has experienced abnormally dry conditions.

The US Farm Services Agency has offered farmers and ranchers in the affected areas financial aid to help them cope with the extreme conditions, which had parched the land since the beginning of the year.

It was not only farmland that was affected, as Ms Smith explained.

"With this drought, we have seen deer and coyote move into urban areas to seek food and water. It has been an ongoing situation, but it might worsen as a result of the wildfires throughout southern California."

She said the lack of rain was a "big unknown" as far as the recovery of the landscape was concerned.

"It could go both ways. A continuation of the drought could certainly affect the recovery, but on the other hand tremendous rainfall also poses problems as regards to problematic weed species and landslides."

The US Geological Survey (USGS) has established a multi-agency Landslide Hazards Program to assess the risks of "debris flows" in the aftermath of wildfires in southern California and other parts of the US's western region.

In a fact-sheet, the USGS describes debris flows as "one of the most dangerous post-fire hazards... because they tend to occur with little warning".

The landscape after a large fire lacks the vegetative cover to absorb heavy rainfalls, leaving it vulnerable to surface erosion caused by rain run-off.

But the likelihood of heavy rain in the coming months appears to be remote, according to an outlook published by the US Drought Monitor.

Smoke billowing into the sky (Getty Images)
Urban sprawl is moving homes into wildfire territory, say researchers
It shows the drought in southern California remaining until at least the start of next year, and possibly intensifying.

This would leave the region exposed to the risk of further wildfires, especially if the dry, seasonal wind, called the Santa Ana, was to pick up strength again.

Earlier this year, a team of US and French researchers published a paper that suggested that the risk of wildfires increased when urban areas encroached on natural habitats.

They said that 39% of US homes were located in what they called the "wildland-urban interface" (WUI).

Writing in the Proceedings of the National Academy of Sciences (PNAS), they suggested that trees and scrub alongside people's homes created an environment in which wildfires could spread rapidly.

The researchers added that tighter building regulations for properties within the WUI could "reduce or mitigate fire risks in these areas".

However, Trish Smith observed: "There is not much we can do to change the fire ecology because our natural systems here have evolved with fire.

"But we can do our best to work with local agencies to plan our urban developments to reduce the impact of future wildfires on our human and natural communities."

Map showing drought outlook for western US states (Source: Noaa)

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