Many charcoal burners had previously been farmers but had given it up - they couldn't predict the rains any more due to the changing seasons, so their crops failed and yielded nothing.
The Spiny Forest is like nowhere else on Earth, but it's disappearing fast.
It's a bizarre Dr Seussian world of spiky octopus trees and swollen baobabs, and almost all its species exist only in Madagascar.
Once there were ten-foot tall elephant birds and gorilla-sized lemurs too, but they went extinct just a few centuries ago.
Unsurprisingly, scientists have long ranked the Spiny Forest as one of the world's most important 'ecoregions'. Even so, hardly anyone outside Madagascar has heard of it. The tragedy is that the Spiny Forest is rapidly, silently, going up in smoke while the world looks the other way.
Southern Madagascar is a dry and impoverished region with little in the way of infrastructure or industry. Most of the population scrapes a living from the land, as cattle herders and farmers, or as fishermen at sea. People also depend on the forest's essential resources, such as construction wood and fuel, medicinal plants, wild yams and 'bushmeat', among other things.
So why is it disappearing so fast?
There are two main causes of deforestation - shifting cultivation (also known as slash-and-burn agriculture), and the production of charcoal. Here charcoal is not just a novelty for barbecues, but the fuel that cooks almost every meal. Making it involves baking the Spiny Forest's precious hardwood trees in makeshift earth ovens, and it's a gruelling job. Nonetheless, it's a growing menace.
In 2010 my colleagues at the WWF noticed a huge increase in the amount of charcoal being produced in the forest of Ranobe. Ranobe is the richest area in the whole Spiny Forest for lemurs and other wildlife, and it had just been declared a new protected area, so we needed to find out what was going on.
I wanted to know what had driven the change, so I interviewed more than 200 charcoal producers to find out. Many had previously been farmers but had given it up - they couldn't predict the rains any more due to the changing seasons, so their crops failed and yielded nothing. Even areas with irrigation suffered, as the region's few ageing dams and canals had fallen into disrepair.
Nor was it just the farmers who were suffering. Some charcoal makers had been fishermen, but decades of overfishing meant there weren't enough fish left to catch. Others had been herders, but had lost their cattle to rustlers. With growing families and rising costs of living, money was an issue for everyone, and traditional ways of life just weren't paying the bills anymore.
The exploitable resource of last resort
With nowhere else to turn, desperate communities were descending on the Spiny Forest. The forest, it seems, acts as a safety net. Rural Malagasy people don't want to produce charcoal or carry out shifting cultivation; they'd rather farm, fish, or find a salaried job.
Unfortunately, there simply aren't many options in the Spiny Forest, and the importance of the forest as a backup seems set to grow as climate change continues to disrupt the region's weather. The trouble is, practices like charcoal production are tearing huge holes in the forest safety net.
However, all is not yet lost. Hundreds of dedicated conservationists are working up and down the island, developing innovative solutions to the nation's environmental crisis. What's more, the Malagasy government has spent the past decade creating dozens of new parks and reserves, including several in the Spiny Forest.
The tide may be starting to turn, but these efforts need the support of the world. Can we save the Spiny Forest and the safety net it provides?
Charlie Gardner is Honorary Research Fellow in Biodiversity Management, University of Kent.