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Author(s): International Union of Forest Research Organizations (IUFRO)
Editorial office: WSL, Switzerland
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Climate change: Forests as a major keeper of greenhouse gases at risk of being lost entirely

Klimawandel: Wälder könnten verloren gehen
Fig. 1 - The trees and soils of the world’s forests are capturing and storing more than a quarter of the world’s carbon emissions.
Photo: Reinhard Lässig (WSL)
 
Klimawandel: Wälder könnten verloren gehen
Fig. 2 - Climate change is modifying forests. In the canton of Valais (Switzerland), for example, more and more Scots pines are dying. Pubescent oak, however, is becoming more frequent.
Photo: Ulrich Wasem (WSL)
 
Klimawandel: Wälder könnten verloren gehen
Fig. 3 - In certain areas, climate change could lead to substantial gains in the supply of timber.
Photo: Reinhard Lässig (WSL)

Forests might lose their critical role as massive sinks for absorbing greenhouse gases. Climate change-induced environmental stresses threaten to damage forests and even decimate them worldwide. This is arising from the report "Adaptation of Forests and People to Climate Change – A Global Assessment" which was presented at the United Nation’s Forest Forum.

The study was coordinated by the Vienna-based International Union of Forest Research Organizations (IUFRO) through the Collaborative Partnership on Forests (CPF), an alliance of 14 international organizations that each has substantial forestry programs. Authored by 35 of the world’s top forestry scientists, it provides the first global assessment to date of the ability of forests to adapt to climate change.

Forests are suffering from climate change

"We normally think of forests as putting the brakes on global warming, but in fact over the next few decades, damage induced by climate change could cause forests to release huge quantities of carbon and create a situation in which they do more to accelerate warming than to slow it down," said Risto Seppälä, a professor at the Finnish Forest Research Institute (Metla), who chaired the expert panel that produced the report.

The analysis shows that, whilst negotiating the details of the climate convention, officials also must consider how the world’s forests are likely to suffer – and perhaps severely – as the earth gets warmer.

Due to higher temperatures the regulation function might be lost

While deforestation is responsible for about 20 percent of greenhouse gases, overall, forests currently absorb more carbon than they emit. The trees and soils of the world’s forests are capturing and storing more than a quarter of the world’s carbon emissions. The problem, scientists say, is that this critical carbon-regulating service could be lost entirely if the earth heats up 2.5 degrees Celsius (4.5 degrees Fahrenheit) or more relative to pre-industrial levels.

The study notes that the higher temperatures – along with the prolonged droughts, more intense pest invasions, and other environmental stresses that could accompany climate change – would lead to considerable forest destruction and degradation. This could create a dangerous feedback loop in which damage to forests from climate change significantly increases global carbon emissions which then exacerbate the greenhouse effect.

The authors of the report noted that the impacts in different ecosystems would vary over time. In fact, the authors found that the risk of losing forests as a net carbon sink is significant even in relatively conservative scenarios in which countries achieve modest emissions reductions and stabilize greenhouse gas concentrations. At the moment there still is an upward trend of emitting gases.

Threats, but also benefits, of climate change

The study observes that as climate change progresses over the next decades:

  • Droughts are projected to become more intense and frequent in subtropical and southern temperate forests, especially in the western United States, northern China, southern Europe and the Mediterranean, subtropical Africa, Central America and Australia. "These droughts will also increase the prevalence of fire and predispose large areas of forest to pests and pathogens," the study says.
  • In some arid and semi-arid environments, such as the interior of the American west, forestry experts worry that climate change could be so dramatic that timber productivity could “decline to the extent that forests are no longer viable.”
  • Decreased rainfall and more severe droughts are expected to be particularly stressful for forest-dependent people in Africa.
  • In certain areas, climate change could lead to substantial gains in the supply of timber. The combination of warming temperatures and the fertilizing effect of increased carbon in the atmosphere could fuel a northward expansion of what is known as the boreal forest, the coniferous timber lands that run across the earth’s northern latitudes and include forests in Canada, Finland, Russia and Sweden.

The scientists warn that efforts to adapt to climate change may end up providing forests with only a temporary respite. "Even if adaptation measures are fully implemented, unmitigated climate change would, during the course of the current century, exceed the adaptive capacity of many forests," said Professor Andreas Fischlin of the Swiss Federal Institute of Technology in Zurich, who is one of the lead authors of the study and a coordinating lead author with the IPCC. "The only way to ensure that forests do not suffer unprecedented harm is to achieve large reductions in greenhouse gas emissions."

Political action is needed

Forestry experts acknowledge that more research is needed to better understand precisely how climate change will impact forests and how effective different adaptation responses will be. But they say the challenge to policy makers is that they must act even in the face of imperfect data because “climate change is progressing too quickly to postpone action.”

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