Most people are now aware that the world’s hunger for energy from fossil fuel is leading to catastrophic climate change. What is becoming increasingly clear however is the effect that forests have on the climate and the climate has on forests (see below).

Forests’ effect on the climate

Forests play an important role in regulating the earth's temperature and weather patterns by storing large quantities of carbon and water. This regulatory function has a profound effect on both the local and the global climate.

Locally, trees provide shade, which in turn lowers summer temperatures and prevents the soil from drying out, they reduce heat loss from the ground in winter and prevent storm damage by providing shelter from wind.

Globally, forests regulate the global carbon cycle, having a profound effect on the climate. As well as this, deforestation is also driving climate change at an alarming rate. Indeed the CO₂ released each year from deforestation and degradation is higher than that released by our yearly transport emissions. The continued existence of forests is particularly necessary if we are to halt what is known as runaway climate change. Runaway climate change is the point whereby increases in temperature lead to more GHG emissions which in turn leads to increased temperatures. Examples of this include that increased temperatures will melt ice caps which will lead to huge increases in the release of GHGs; and increases in temperature are projected to negatively affect up to two-thirds of existing forests, thereby exacerbating deforestation and increasing the release of carbon.

The climate’s effect on forests

Global warming, which on a geological timescale is occurring in the equivalent of a split second, is significantly disrupting the intricate and poorly understood web of interactions that governs the very structure and composition of forest ecosystems. This means that around a third of today's forests are likely to change their species composition. A temperature increase of 3°C by 2100 would result in forest ecosystems moving 500 km towards the poles or 500m in elevation in order to find the same climatic conditions. Such distances are far beyond the average rate of dispersal for individual tree species, let alone entire forest ecosystems.

Early warnings about the consequences of the impacts of climate change on forests have been documented in, among others, The Carbon Bomb: Climate change and the fate of the northern Boreal forests - a 1994 Greenpeace report which states on page 2 that:

"Studies on the global carbon cycle suggest that boreal forests are not absorbing as much carbon as they did before 1976. As a result, the atmosphere already appears to contain 10-15 billion tonnes of carbon more than it would have if forests had continued to absorb carbon at the pre-1976 rate. If boreal forests continue to decline, estimates suggest that burning and rotting of boreal forests could contribute to the release of up to 225 billion tones of extra carbon into the atmosphere, increasing current levels by a third. This would accelerate the rate of climate change."

While it is possible that the boreal forest could expand into the frozen tundra as temperatures increase, such an expansion would likely be delayed by slow tree migration rates. Even in the long-term, the boreal forest is unlikely to move northward fast enough to compensate for the breakdown of boreal forests at the southern part, turning dense forest into open woodlands and grassland, which in turn will result in a lowered biological diversity and a reduced ability of these ecosystems to store carbon and water.

Other forest ecosystems are faced with a similar fate; according to the Intergovernmental Panel on Climate Change (IPCC), a UN panel of climate scientists, it is likely that many tree species will not be able to change their geographic distribution fast enough to keep up with projected shifts in suitable climate and extinctions are expected to occur.

What can be done?

So trees (or the lack of them) are one of the key problems that must be tackled if we are to minimise the effects of climate change. It is not surprising then that many have also suggested that planting trees (carbon sinks) or reducing emissions from deforestation and degradation (REDD) are among the solutions to our climate crisis. SinksWatch believes however that if great care is not taken, more harm than good could be caused by both of these schemes, especially if they lead to the continuing emergence of large-scale industrial tree plantations. SinksWatch believes that all global efforts to halt climate change should concentrate on reducing emissions and avoiding deforestation and degradation entirely.