The Forests Behind the Fires

Today's guest blogger is Prof. Dan Yakir. Until recently, Yakir was head of the Environmental Sciences and Energy Research Department at the Institute, and he heads the Yatir Forest research station, which monitors, among other things, carbon exchange in a man-made semi-arid pine forest.

This piece comes in the wake of the worst fire in Israel's history, in which extreme drought, winds and a long fire season that depleted fire retardant supplies combined to flame a few embers into a major conflagration that burned thousands of acres of natural scrub forest.Tens of human lives were lost, many homes destroyed and the city of Haifa threatened, and now, predictably, government response has focused on shifting blame. Forgotten in the media fest is the forest itself....

Following the recent forest fires in Israel's Carmel region, attention has naturally focused on the loss of human life and on the national fire-fighting capabilities or lack thereof. But forest fires have significance in and of themselves.

The first effect of burning trees is smoke. Smoke obscures the sun. But instead of reflecting back sunlight and cooling the surface, smoke "clouds" are loaded with black soot that absorbs sunlight, warming the atmosphere. On large scale, this influences weather, rainfall and climate. Soot is also composed of nanoparticles that harm our respiratory systems. In addition, forest fires produce poison gases, such as methane, CO, NOx, ozone. But when the smoke clears and the particles settle, we are left with CO2: Most of the wood is burned into this notorious greenhouse gas. From our local fire, tons of CO2 mix into the global atmosphere.

Based on our measurements, a dunam (~1/4 acre) of Mediterranean pine forest absorbs 840 kg of atmospheric CO2 per year. We can do the math: The forest is about 50 years old; the area burned was about 40,000 dunams; more than half of the carbon remains protected below ground and in the dead wood. By rough estimation, nearly 500,000 tons of CO2 were released in the fire.

Sounds like a lot. Actually, it is about 1/2% of the "regular" annual CO2 emission in Israel. Not to play down the fire's devastation, but our regular energy use produces the CO2 equivalent of 150 Carmel forest fires every year.

Of course Israel, with or without fires, is a very small part of a world-wide problem. The global network in which my team and I take part monitors atmospheric greenhouse gases; and it just released its data for 2009: Humanity emitted nearly 30 billion tons of CO2 just from burning fossil fuel. Adding forests into the equation, we find two effects. First, as recent events demonstrated, forests burn spectacularly -- not only in Israel, and often due to such natural causes as lightning. But conversion of forest to cropland is a major source of forest fire, pushing up CO2 emissions. In the past, Europe and North America were largely deforested; today, the same is taking place in the tropics. Globally, forest fires add about another 4 billion tons of CO2 every year.

But now comes the good part: As noted above, forests absorb large quantities of CO2. Surprisingly, we found that the value used above for Israel holds for the average forest, world-wide. That means the forests of the world absorb about 9 billion tons of heat-trapping CO2 gas each year. That's equivalent to almost 1/3 of humanity's energy-use emissions -- much more than the amount released by burning forests. In other words, forests are our real friends - more so than we normally realize. Forests in Israel, which are managed by the dedicated forestry staff of the JNF-KKL, serve as models for the potential of expanding forests into the dry regions covering some 18% of the planet's land area.