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Will Haiyan’s impact in the Philippines be worsened by deforestation?

While it’s too early to assess the impact of Super Typhoon Haiyan — reportedly the strongest tropical storm ever recorded to make landfall — in the Philippines, the damage could be exacerbated by the large-scale loss of the country’s forests.

According to the national Forest Management Bureau, forest cover in the Philippines declined from 21 million hectares, or 70% of the its land area, in 1900 to about 6.5 million hectares by 2007, mostly due to intensive logging and subsequent conversion to agriculture. That loss has led to extremely high rates of soil erosion and has likely contributed to the Philippines’ high number of flood-related disasters, which kill hundreds on a near-annual basis.

Typhoon Haiyan.
Typhoon Haiyan — known as locally Yolanda — made landfall at 4:40 a.m. local time on November 7 packing sustained winds of 235 kilometers (145 miles) per hour and gusts to 275 kilometers (170 miles) per hour. This image was captured by NASA’s Aqua satellite on Nov 8.

Removal of tree cover and other vegetation, especially in landslide-prone mountainous areas, worsens flooding by increasing the rate of water runoff. A 2007 study published in the journal Global Change Biology, found that a 10 percent increase in deforestation results in a 4-28 percent increase in flood frequency. Given that the Philippines has lost nearly 50 percent of its forest cover, the impact of deforestation on flooding is potentially very substantial, if difficult to quantify.

Accordingly, in recent years the Philippine government has taken steps to slow and in some cases reverse forest loss across the archipelago. In 2011, President Aquino issued a nation-wide ban on logging in natural forests. Nonetheless the ban has been poorly enforced and forests are still being stripped for mining and converted for plantations.

Conversion to plantations is notable because the 2007 study found that monocultures can actually heighten flood risk relative to natural forests.

“An important additional finding was that only the amount of native forest was correlated with reductions in flood risk — plantation forests had the opposite effect”, said lead author Cory Bradshaw at the time. “Promoting native forest conservation also has the added benefits of slowing climate change by storing huge quantities of carbon, reducing wildfires, and conserving species.”

Historic deforestation in the Philippines
Historic deforestation in the Philippines

The distinction is important if the Philippines aims to brace itself for more storms like Haiyan in the future. A growing body of research suggest rising greenhouse gas levels and associated increases in sea temperature will lead to stronger and more frequent tropical storms. That potentially means more Haiyans for the Philippines in the future.

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