Each year, 130,000 square kilometres of rainforest is destroyed throughout the world. Most of the areas cleared are used for agricultural purposes. This also applies to the rainforests in the mountainous regions. However, the land is quickly reclaimed by weeds, in particular by bracken, a plant that neither herbicides nor burning can get rid of permanently. This is why farmers often give up the land again after a few years – only in order to deforest new areas.
"This is a vicious circle that needs to be broken,” says Professor Thomas Knoke of the Institute of Forestry Management at “Technische Universität München”, Germany. He is the lead author of the study “Afforestation or intense pasturing improve the ecological and economic value of abandoned tropical farmlands”, which was published in Nature Communications in November. The study is based on surveys examining whether and how abandoned pastureland can be recultivated.
According to the scientist, the various concepts are assessed not only in terms of their economic benefits – for the first time, ecological and sociocultural criteria have been addressed as well. These include e.g. carbon and nitrogen capture in plants and in the soil, biomass production, soil quality, impacts on the climate and the hydrologic balance as well as acceptance by farmers.
The area examined (approx. 150 hectares) is located in the Ecuadorian Andes at an altitude of 1,800 to 2,100 metres. The researchers examined five different concepts:
Afforestation with alder and pine has proved to be particularly sustainable. In the long term, forested regions are also the best protection against erosion. “Also, our study demonstrates that afforestation with the indigenous Andes alder influences water regulation significantly more favourably than the other use options,” explains Project Spokesman Professor Jörg Bendix of the University of Marburg.
In addition, typical rainforest plants and animals can gradually re-establish themselves in the afforested regions. As the study further revealed, intensively used pastureland scored a significantly better ecological value than extensive pastoralism. The economic benefits are provided by the sale of timber (afforestation) or of meat and milk (pastureland). Alder plantations showed the greatest yields.
Thanks to the better eco-balance of forests and improvements in income opportunities in the long term, most of the livestock owners also regard afforestation as the use option of choice, as interviews in the course of the study revealed. The scientists stressed that in order to secure the success of recultivation concepts, the users should always be involved as well.
However, the sustainable use concepts do entail costs. Calculated over a twenty-year period, farmers doing without slash-and-burn methods have a lower income each year: 87 US dollars (USD) per hectare in afforestation and 100 USD per hectare in intensive pastoralism. The scientists believe that compensatory payments for recultivation are an important incentive to replant former pastureland. Here, CO2 certificate trading could provide an additional source of income in the long run.
The researchers also regard their study as a model for the assessment of recultivation concepts in other tropical mountain forests, e.g. in Brazil or Africa. “Abandoned agricultural land offers a gigantic natural resource that has so far remained unused,” Thomas Knoke concludes. “Projects supported by the German Research Foundation are currently in progress in order to implement the results of the study together with farmers in Ecuador,” Professor Erwin Beck of the University of Bamberg adds. He initiated the study in Bamberg 17 years ago.
*Scientists at the following institutions were involved in the study: Technische Universität München; University of Bayreuth; University of Marburg; University of Erlangen/Nuremberg; Technische Universität Dresden; Justus Liebig University Gießen; National University of Loja, Ecuador; Universidad Técnica Particular de Loja, Ecuador; FLACSO, Quito, Ecuador; CATIE, Turrialba, Costa Rica.
Publication: Nature plants
More Information: TUM