What impact do modern crops have on deforestation in the Democratic Republic of Congo?

Increasing the productivity and income of small-scale farmers is often seen as a central element in the fight against poverty and hunger. To this end, significant investments have been made in international agricultural research and, in particular, in the development, adaptation and promotion of modern crop varieties in combination with chemical fertilisers. This Green Revolution has resulted in increased yields and overall production between 1960 and 2000 in Asia and Latin America, but it has had fewer benefits in sub-Saharan Africa, where the dissemination of modern crop varieties remains limited to this day, and agricultural yields are much lower than in other regions.

The "second lung" of the planet after the Amazon rainforest, the Congo Basin forest is one of the world's major biodiversity reserves and the second largest carbon sink. It is also one of the poorest regions in the world, where fragile agriculture is the main means of subsistence. It is in this context that Sylvie Lambert and Karen Macours, economists at INRAE (PjSE unit) and their colleagues Tanguy Bernard from the University of Bordeaux and Margaux Vinez from the World Bank studied a large government programme that provided subsidies for improved crop varieties to Congolese smallholders.

While the positive effect of the dissemination of modern crop varieties on the economic well-being of populations is now proven, it is also often seen as contributing to forest conservation. This issue is of great political importance given that land-use change is the second largest source of human-induced greenhouse gas emissions worldwide, that tropical forests are home to at least two-thirds of the world's biodiversity, and that agricultural expansion is the main cause of tropical deforestation and biodiversity loss. The impact of the introduction of yield-enhancing technologies on deforestation in a given area is ambiguous, as under certain input and labour market conditions, farmers may be driven to cultivate the richest soils, which may lead to further land conversion and deforestation.

To shed light on this issue, the researchers conducted a randomised controlled trial to study the impact of the dissemination of modern crop varieties on deforestation in the Democratic Republic of Congo (DRC). The study was conducted in a remote area with weak input and output markets. No chemical fertiliser is available to small-scale farmers in the area. The study focused on a subsidy programme for improved crop varieties of rice (short cycle), maize (high yield), groundnuts (high yield) and cassava (disease resistant).

This study highlights the importance of distinguishing deforestation of primary and secondary forests. According to international definitions, a primary forest is a forest with no observable traces of cultivation, while a secondary forest is the result of a more recent regrowth on land that was previously cultivated. The distinction between these two types of forest is relevant as deforestation of primary forests has important consequences for carbon storage and biodiversity. This distinction is also relevant for farmers' decision making, as they know that cereals have high soil nutrient requirements. Thus, in the absence of fertilisers (mineral or organic) and soil conservation practices, farmers may decide to cultivate the most fertile soils in order to grow their improved cereals, and therefore move towards cultivating deforested primary forest land, where soils are richer in nitrogen. On the other hand, in villages where farmers have had access mainly to leguminous seeds that can fix nitrogen from the air (mainly groundnuts), deforestation of primary forests has been more limited. As a result, the risk of deforestation of primary forests is likely to be sensitive to the type of crop used.

By mobilising plot-level land conversion data, combined with remote sensing data, the researchers found that, overall, the promotion of modern crop varieties did not lead to an increase in land demand and corresponding deforestation, but neither did it reduce the land used for agriculture. The results of this research also show that subsidising modern crop varieties led to increased deforestation of primary forests by beneficiary households. The authors conclude that policies to promote modern crop varieties in isolation may come at the cost of significant biodiversity losses. 
This work contributes to current debates on sustainable intensification practices that aim to reduce productivity-environment trade-offs by moving away from the use of improved varieties and mineral fertilisers, and by moving towards context-specific responses, including organic fertilisers and alternative soil fertility management practices. If policy-makers seek to achieve the dual objective of increasing productivity and preserving primary forests, increased access to modern crop varieties should be combined with the promotion of sustainable technologies and practices to maintain soil fertility or focus on crops that are less demanding in terms of soil nutrient requirements.