Not All Forests Are Created Equal: Reforesting the Tropics for People, Biodiversity, and Carbon

August 14, 2014 | 2:23 pm
UCS Science Network

It’s after sunset and getting dark fast. The electricity is out—again—so a single candle casts a small pool of light on my survey papers. Chickens peck around my feet in the dirt-floor kitchen. Wood smoke and mouthwatering wafts of dinner fill the cool Andean air.

Up since 5 a.m. surveying trees and interviewing farmers, I’m less focused on the quaint scene than on finishing my last survey and starting my three-mile walk home in the dark. But my squat, enthusiastic interviewee, Ecuador’s answer to Joe Pesci, is holding forth on a subject dear to him.

“Why plant trees?” he asks rhetorically for the umpteenth time. He’s standing now, gesturing emphatically. “Because they give us WATER!”

(photo credit Jake Brennan)

(photo credit Jake Brennan)

This man sure loves trees. And in Intag, a rural Andean community in northwest Ecuador, he’s not the only one.

Only thirty years ago, the landscape here was covered in dense cloud forest. One of the most biodiverse ecosystems on the planet, cloud forests play their vital role in the hydrological cycle uniquely, capturing water from passing clouds and mist. After clearing 90% of their forests for fields and pasture, these communities began to experience severe water shortages.

Faced with abandoning ship for the city or overhauling their relationship to their native land, the locals turned to planting trees. In just five years they restored forests to over 30 hectares of degraded, low-productivity pasture. They also planted trees on farms in new and innovative ways, producing everything from increased soil nitrogen to exotic fruits. The resulting landscape is a mosaic of forest types, all with different species, levels of biodiversity, and local uses. 

Tropical forests are growing back

Even as humans continue to clear 13 million hectares every year, forests are growing back across the tropics. In addition to helping local communities like Intag, secondary forests can conserve tropical biodiversity.

Tropical trees are also highly efficient carbon sequestration machines, using light to rapidly convert carbon dioxide into wood. The only socially acceptable form of geoengineering, planting trees is an attractive tool to combat climate change. With their fast growth rates, tropical trees take center stage in global policies, such as REDD+, that promote reforestation to sequester carbon.

As in temperate areas, forests return when people decide to replant or to abandon the land. A century ago, the northeastern United States was almost completely deforested. As settlers expanded to the flat, fertile Midwest, the hilly Northeast became less profitable and was abandoned, leaving nature to take over. Today, it is one of the most forested parts of the country.

In China today, we see a different reforestation scenario. Massive deforestation left many areas with eroded soils and severe local timber shortages, spurring the government to plant millions of (mainly fast-growing, non-native) trees in one of the largest reforestation schemes in history.

These two forest recovery pathways—land abandonment and intentional replanting—have been repeated throughout history. The secondary forests they produce are different—both from the primary forests that used to occupy the landscape, and from each other. These differences have a huge impact on both global biodiversity and on the lives and livelihoods of rural people.

Not all forests are created equal

Local Intag resident spends a ‘minga’ (community work) day cutting back pasture grass encroaching on saplings the community has planted. The community holds about 50 such mingas per year. (photo credit Jake Brennan)

Local Intag resident spends a ‘minga’ (community work) day cutting back pasture grass encroaching on saplings the community has planted. The community holds about 50 such mingas per year. (photo credit Jake Brennan)

To the people of Intag, the differences between forest types are obvious. But at the upper levels of forest policy, they can look quite similar. ‘Forest’—commonly defined as an area with more than 10% tree cover—can mean everything from tropical rainforests to sub-artic evergreens to, controversially, palm oil plantations. To either a farmer or a forest animal, these forests are distinct, providing very different goods, services, and access. Because tropical forests house over half of the world’s terrestrial species, and over 800 million people currently depend on them for their livelihoods, we need to understand how each type of secondary forest benefits people, conserves biodiversity, and sequesters carbon.

In the tropics, industrial timber plantations—stands of a single, non-native tree species—are timber-producing, carbon-sequestering machines. But, they also support far fewer species than most natural forests. Fewer species means lower resilience: more vulnerable to fire, wind, pest outbreaks and disease, plantations provide less stable stores of carbon. Local people can harvest and sell timber (or carbon) if they have the land and money to establish plantations. But, lower tree and plant diversity also means there are fewer possible local uses.

Secondary forests can also grow back on abandoned land. People use many of the fast-growing species that recover in these forests for food, medicine, and firewood. Although these species are often different species from primary forests, they can still sequester large amounts of carbon. But, in some places, land is so degraded that forests cannot recover unassisted. Here, restoring forests by planting native trees and allowing others to grow in their shade can stimulate forest regrowth, while also allowing people to add species that are important for conservation, or sequester carbon quickly.

Finally, small-scale farmers have been planting trees for food, timber, soils and aesthetics in their gardens and landscapes for centuries. Geared primarily towards improving or sustaining agricultural production, these agroforests can also be highly biodiverse, but with combinations of species that are often different from those in primary forests.

Reforesting the tropics shouldn’t be a one-size-fits all approach

Different forests provide different things to different people. For my Ecuadorian friend, replanting trees in deforested landscapes means access to water—and a way to conserve rural farming culture. But needs vary from place to place. Reforesting the tropics cannot be a one-size-fits-all approach. Each type of secondary forest above produces different products, levels of biodiversity, and levels of accessibility for local people. Determining what stakeholders need in a given context is a crucial first step to deciding how, when, and where to reforest.

How can you make a difference? If you plan to buy carbon offsets for your next trip or purchase, search for companies that support local restoration or tree planting efforts in rural communities. You can also purchase or promote projects that make use of sustainably sourced wood. Another way to make a difference when it comes to deforestation and reforestation is by educating children and communities about the environment and the role of science in their daily lives.