Keijzer calls tropical reforestation "low fruit" for two reasons: "First, because you create economic values for the countries that need it most, so it is an opportunity to get millions of people out of extreme poverty." Secondly, he points out that "if you wanted to plant a tree in Belgium, for example, you would probably spend more than 10 euros per tree if not 15", but in tropical regions "you can plant it for half a dollar."
But tropical reforestation may require significant research, so projects must be realistic about what they can achieve. "There are very few parts of the tropics where there is enough experience and knowledge to recover large-scale native forests," says Andrew Marshall, head of the non-profit ecological restoration organization Reforest Africa.
Compare the United Kingdom, where there are less than 20 species of native trees across the country, with Tanzania, which has the same amount of diversity in a single acre. "You are talking about hundreds of species for which you need to obtain methods and / or solve a few that grow well and the others return," he says. "You can't work with everything."
How exactly forest Land restoration depends on two key factors: what it looks like today and what the ultimate goal of reforestation is.
The land could already house a degraded forest, with less tree cover, fewer species and poorer soil. It may have been deforested, where many trees have been felled and the land is used primarily for another purpose, such as agriculture or infrastructure. It could be dominated by an invasive species such as lianas, the large woody vines that Tarzan sways and that can quickly take over tropical lands, or molinia, an herb that stretches through the Welsh highlands after the fields leave to graze
In the most extreme cases, the earth may have become unable to harbor life, but Keijzer says he has never encountered a place that cannot be restored.
In theory, reforestation in many places could be achieved through natural regeneration, where the earth is allowed to return to the forest with minimal human intervention. "The safest way to do this is to find places that recover naturally and areas that are already close to other forest areas, areas that have recently been cleared," says Marshall. "Because one would expect that there would still be some seeds in the ground and birds and wildlife would disperse the seeds."
This option also has the benefit of being cheap, but letting nature take its course is not always feasible for a combination of practical, social and economic reasons, and a helping hand is often needed. On the other side of the Sahel Desert, in North Africa, farmers are successfully using a managed natural regeneration technique in which they carefully take care of the remains of old tree roots under the ground to bring the trees back to life. .
Afforestt, a company based in India that operates worldwide, has developed an artificial formula for the soil that consists of preparing a compost "tea" full of microorganisms.
And in other places the most advanced technologies are playing an important role. Mangrove trees in Myanmar have been planted with drones designed by the UK-based Dendra Systems startup (formerly known as Biocarbon Engineering) to burn seeds directly in the fields, for example.
Afforestt founder Shubhendu Sharma sees value in this diversity of approaches: "There are 100 ways to recover a lost forest," he says. "Like religion, there is a god and different paths to get to that."
Experts agree that The ultimate goal should be to make the forest sustainable in the long term, which means weighing global, national and local interests.
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