BOGOR, Indonesia (16 September, 2013)_When natural forests are threatened by deforestation or climate change, the best hope for the survival of certain at risk tree species may be to include them in agroforestry plots managed by small farmers, according to new research.
Tree species can be conserved in three ways, according to a recent review in Biodiversity and Conservation by scientists at the Center for International Forestry Research (CIFOR) and the World Agroforestry Center (ICRAF).
They can be left to grow in their native, natural habitat, which is known as conservation in situ, or “in their original place”.
If trees are valuable because they produce timber, fruit or other commodities, farmers may transplant them to nearby agroforestry plots, a technique known as conservation circa situm, meaning “close to their place of origin”.
Or, they may be conserved in seed or gene banks, known as conservation ex situ, or “outside their original habitat”.
The three types of conservation are interrelated, and smallholders play a role in each of them, but scientists actually know very little about the extent and the limitations of those connections and how effective they are, said Manuel Guariguata, a principal scientist with CIFOR.
“We know that agroforests can be very diverse, but we don’t really know the dynamics of the links between farms and natural ecosystems,” he said.
“For example, we don’t know exactly what happens with timber and other species in the wild when smallholders domesticate them by planting them outside their natural habitat.”
If a species is to survive, its population must be large enough to allow for genetic diversity, but more research is needed to determine how well small agroforestry farms contribute to conservation, the paper said.
“Conventional wisdom is that if you plant trees in plantation or agroforestry systems, it will contribute to conservation of natural stands of trees,” said Ian Dawson of the World Agroforestry Center, the lead author of the paper.
People are expected to harvest trees from plantations or agroforestry plots, leaving the natural forest intact, but there is little research to support that assumption, he said, adding that “it may be that people take it for granted and don’t think they need to study the link.”
“We need a better understanding of the relationship between agroforestry practices in one location and conservation in an adjacent natural forest or woodland,” Dawson said.
Farmers who combine agriculture and forestry can contribute to conservation in several ways, but it is important to look at how the different approaches work together to ensure the greatest benefit with the fewest unintended consequences, Guariguata said.
Agroforestry plots may serve as “stepping stones”, allowing bees, birds and animals to disperse pollen or seeds as they move through them into natural forest areas – a process that can result in tree reproduction in both land types.
In places where certain species in natural forests cannot adapt to the pace of climate change, conservation on agroforestry plots may offer the only chance for survival, Dawson said.
Scientists need more information about how different species reproduce and about population density – the number of trees of a certain species in a particular area that are necessary for sustainability, he said.