Protecting rainforest through agriculture and forestry

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Afforestation and intense pasturing can effectively increase the environmental and economic value of abandoned farmland, according to an international research team investigating means to counteract the clearing of tropical mountain forests in Ecuador.

A woman milking a cow, together with two children and a man, in a mountainous pasture area of cleared rainforest.

Every year, 130,000 square kilometres of rainforest disappear from the face of the earth – an area equivalent to the size of Greece. The majority of this land is cleared for agricultural development – even in tropical mountain areas. Unfortunately, these fields are quickly overgrown with stubborn weeds. As a result, farmers often abandon the land after a few years and start clearing new areas of forest.

“This cycle has to be broken,” says Thomas Knoke, a professor in forest management at Technische Universität München (TUM) and lead author of a study recently been published in Nature Communications. “We’ve been investigating whether this abandoned pasture land can be recultivated, and if so, how.”

Overgrowth of bracken in a cleared rainforest area.

Rainforest areas cleared to be used as agricultural land are quickly overgrown with tenacious weeds such as bracken, which can’t be permanently eliminated using herbicides or by burning the land. (Photo: Jörg Bendix/Universität Marburg.)

The team, consisting of researchers from several universities in Germany, Ecuador and Costa Rica, did not just look at economic benefits when evaluating the different concepts.

Also considering environmental and socio-cultural criteria, they factored in issues such as the amount of carbon dioxide and nitrogen assimilated by plants and soil, biomass production, soil quality, impact on climate, water management and acceptance among farmers.

Sustainable land use

The researchers investigated an area of around 150 hectares in the Ecuadorian Andes at an altitude of 1,800 to 2,100 metres. They looked at five different concepts:

  • no land use – abandoned land is left to nature
  • afforestation – planting a native species of alder
  • afforestation – introduction of a non-native pine species
  • extensive pasturing – mechanical weed control followed by initial fertilization and land use
  • intense pasturing – chemical weed control and land use with regular fertilization.

Afforestation with alder and pine species proved particularly sustainable. In addition, forested regions offer the best protection against erosion in the long term.

“Our study also showed that afforestation with the native Andean alder had a much more positive impact on the climate and water balance than the other land use options,” says Jörg Bendix, a professor from Phillips-Universität Marburg.

Typical rainforest plants and wildlife are also able to gradually recolonise afforested regions.

Engaging the farmers – a key factor

Intense pasturing scored much higher on the ecological scale than extensive pasturing. Economic benefits stemmed from the sale of wood (afforestation) or the sale of meat and milk (pasturing). Alder plantations achieved the greatest financial returns.

After surveying land users, the researchers found that the majority of livestock farmers also viewed afforestation as the best land use option thanks to the positive ecological balance and greater long-term earnings potential. “If we want recultivation concepts to be a success, the people using the land have to be engaged,” Bendix says.

Reference project for other tropical mountain regions

Slash-and-burn practice in a mountainous rainforest area.

Slash-and-burn is a widespread practice used in rainforests to create space for agricultural development. (Photo: Jörg Bendix/Universität Marburg.)

The sustainable land use concepts all come at a cost, though. Over a period of twenty years, farmers who do not use slash-and-burn techniques are exposed to an annual loss of earnings. This amounts to 87 dollars per hectare for afforestation and 100 dollars per hectare for intense pasturing.

The researchers regard compensation for recultivation as an important incentive for encouraging famers to replant abandoned grazing land. In the long term, trade with CO2 certificates could also provide an additional source of income.

The researchers also believe their study could be used as a reference for evaluating recultivation concepts in other tropical mountain forests, for example in Brazil or Africa. “Abandoned agricultural land is a huge resource that is not being harnessed,” Thomas Knoke says.

Erwin Beck, a professor at the University of Bayreuth who started the project in Ecuador 17 years ago, says the German Research Foundation (DFG), which sponsored the study, is currently funding a number of projects that are working with farmers in Ecuador to implement the findings.

– Adapted from TUM Research News 


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