The largest share of agricultural land in tropical landscapes is managed, not as large-scale industrial plantations, but by smallholders. This Nature Communications article integrates the interdisciplinary research of more than 20 research groups, and seeks to address gaps in our understanding of the ecological impacts of this smallholder-managed agricultural land. The study uses a multifaceted approach to investigating the crop choices that farmers make and how these choices impact on ecological and economic outcomes.
The many interdisciplinary research groups involved in this study conducted an extensive array of experiments and investigations so as to establish a dynamic understanding of land-use, profitability, agricultural inputs and outputs for over 450 Sumatran smallholder households. Methods and techniques applied in order to achieve this included: surveys of farmers; Landsat satellite imagery; biodiversity or genetic diversity measurements of plants, birds, invertebrates and even amoebae and bacteria; measurements of soil water, structure, fertility and functioning; direct recording of local climatic conditions; above and below ground biomass and carbon stock assessment; and measures of net primary productivity. By these methods, the researchers were able to build a picture of productivity, inputs, profitability, land-use change and ecological outputs (biodiversity and ecological services) of four main types of land-use in smallholder dominated mosaic landscapes: forest remnants (i.e. largely untouched patches of rainforest), jungle rubber (i.e. areas of forest with additional cultivated rubber trees), rubber plantations (i.e. rubber tree monoculture), and oil plantations (i.e. oil palm monoculture).
The key findings of the paper are:
- The 75% decrease in unprotected forest between 1990 and 2011 was accompanied by a 30% increase in land cultivated for rubber, a 150% increase in land cultivated for oil palm, and a 300% increase in shrub or bushland (usually land in a transition stage due to be planted with oil palm or rubber). By 2011, a majority of farmers were growing oil palm and/or rubber, most commonly in monoculture.
- Biodiversity and plant genetic diversity was highest in the forest, lowest in the monocultures and intermediate or high in the jungle rubber. The same pattern was also found for micro-climatic stability, soil microbial biomass, microbial decomposer activity, leaf litter, net primary productivity and carbon stocks.
- Conversely, yield was highest in oil palm monoculture, intermediate in rubber monoculture and low in jungle rubber. Oil palm monoculture was also associated with the highest nutrient leaches.
- Switching to monocultural cultivation brought not only substantial economic benefits to farmers, but also higher human welfare to the region (although the authors do not define human welfare or explain how it is quantified).
The authors conclude that economic profitability is, understandably, the major driver behind smallholders’ key decisions regarding land use, and that this drives farmers towards monocultured cultivation of the highly profitable cash-crops rubber and oil palm. Unfortunately, monocultures of these crops are associated with lower ecological ‘health’ since it involves a change in land use from ecologically beneficial forest to monoculture. They strongly recommend very carefully implemented, and locally-relevant, financial incentives to promote forest conservation alongside agriculture, such that actions leading to ecological benefits can also make economic sense for farmers.
Smallholder-dominated agricultural mosaic landscapes are highlighted as model production systems that deliver both economic and ecological goods in tropical agricultural landscapes, but trade-offs underlying current land-use dynamics are poorly known. Here, using the most comprehensive quantification of land-use change and associated bundles of ecosystem functions, services and economic benefits to date, we show that Indonesian smallholders predominantly choose farm portfolios with high economic productivity but low ecological value. The more profitable oil palm and rubber monocultures replace forests and agroforests critical for maintaining above- and below-ground ecological functions and the diversity of most taxa. Between the monocultures, the higher economic performance of oil palm over rubber comes with the reliance on fertilizer inputs and with increased nutrient leaching losses. Strategies to achieve an ecological-economic balance and a sustainable management of tropical smallholder landscapes must be prioritized to avoid further environmental degradation.
Clough, Y., Krishna, V. V., Corre, M.D., Darras, K., Denmead, L.H., Meijide, A., Moser, S., Musshoff, O., Steinebach, S., Veldkamp, E., Allen, K., Barnes, A.D., Breidenbach, N., Brose, U., Buchori, D., Daniel, R., Finkeldey, R., Harahap, I., Hertel, D., Holtkamp, A.M., Hörandl, E., Irawan, B., Jaya, I.N.S., Jochum, M., Klarner, B., Knohl, A., Kotowska, M.M., Krashevska, V., Kreft, H., Kurniawan, S., Leuschner, C., Maraun, M., Melati, D.N., Opfermann, N., Pérez-Cruzado, C., Prabowo, W.E., Rembold, K., Rizali, A., Rubiana, R., Schneider, D., Tjitrosoedirdjo, S.S., Tjoa, A., Tscharntke, T., and Scheu, S. (2016) Land-Use Choices Follow Profitability at the Expense of Ecological Functions in Indonesian Smallholder Landscapes. Nature Communications 7, 13137