In tropical latitudes, months pass without any rain and in the dry season forests become susceptible to fire. These can occur naturally and would normally not pose a serious problem, but clearing land as a result of logging or to make way for plantations is exacerbating the problem and every year the fires spread faster and further.
Greenpeace teams in both Indonesia and Brazil have recorded the scale of the infernos and are clear about the reasons why they are happening. Much of the forests in the Indonesian province of Riau in Sumatra are peatland forests, so normally protected from fire by their boggy biome, but industrial activity has changed all that. The forests are being cleared for plantations of oil palms and acacia pulpwood for paper, creating the perfect conditions for fires at the same time.
"Once these peat swamps are exposed due to logging," Greenpeace forest campaigner Hapsoro explained, "they dry out like a wet sponge exposed to sunlight and become extremely flammable. Once it starts burning, it's very difficult to stop without heavy rain."
The effects of the Indonesian fire also spread across the region. Smoke drifts across South East Asia, clogging the air above the Malaysian peninsular and incurring the wrath of neighbouring governments, and Hapsoro urged the Indonesian authorities to take urgent measures. "The Indonesian government must seriously reconsider allowing any type of land clearing to be done in these areas to minimise the possibility of large and uncontrolled forest fires," he said.
In the Brazilian Amazon, fires have been witnessed in several protected areas and the Greenpeace team sent to investigate also saw rampant deforestation and illegal logging. In the Jamanzim National Forest, using natural resources responsibly is permitted, but intense logging activity has been observed within protected areas.
Both regions boast some of the most diverse varieties of plant and animal life anywhere in the world but fragile habitats, already under pressure from human activities, are being pushed even harder by the increasing number and scale of the fires.
Rainforests play a vital role in regulating the global climate and the more trees that are felled, the more unpredictable the climate will become.
Tropical deforestation accounts for around 20 per cent of global carbon dioxide emissions, a staggering amount that explains why 75 per cent of Brazil's own carbon dioxide contribution comes from forest conversion.
But with drought plaguing many areas - such as last year's catastrophic event in the Amazon - the forests dry out and become even more susceptible to fire. This in turn releases more carbon dioxide and smog into the atmosphere, accelerating climate change and the cycle of destruction continues.
This isn't just a problem for Brazil and Indonesia but for the whole planet. Concrete efforts must be made at a local level to protect rainforests from illegal logging and conversion to plantations, but there must also be international support to back this up. Sustainable management of the forests allows local communities to support themselves and make a living, but the effects of rampant industrialisation are being felt around the world.
