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Department of Geography


Agroforestry and sustainability in the humid tropics

Research in the Cambridge Geography Department on the nutrient dynamics of agroforestry in the humid tropics began more than twenty years ago. Tim Bayliss-Smith, Bryon Bache and Michael Hands secured EU funding for work in Costa Rica, and there was work elsewhere by graduate students including Michael Whittome in Nigeria, Eureka Adomoko in Ghana and Martin Kaonga in Zambia. Based on findings from experimental plots in Costa Rica, our work demonstrated that there was a viable alternative to slash-and-burn shifting cultivation for resource-poor farmers. We showed that maize and beans could be grown in cultivated ‘alleys’ between managed hedgerows, mainly because of the positive effects of managed hedgerows on weed suppression and on the nitrogen and phosphorus cycles. We found that the best species for hedgerows was Inga, a tree that performs remarkably well even on degraded, acidic and nutrient- poor soils. We showed that potentially Inga–based alley cropping could provide sustainable benefits for farmers in humid tropical regions.

Alley cropping farmers

In two subsequent EU projects (1995-2002) the work was transferred from Costa Rica to Honduras and was led by Michael Hands (Senior Research Associate). In Honduras there has been more deforestation than in Costa Rica. Peasant farmers there must cultivate increasingly degraded upland soils, and they have strong incentives to find sustainable alternatives to slash-and-burn cultivation. Michael Hands has continued this work since 2002 through grants from the Kellogg Foundation and other donors, and more recently through The Inga Foundation.


As well as publications, three impacts have arisen from this work:

1. The establishment of an organisation (UK Charity Commission registration 1124688) called The Inga Foundation (TIF). Tim Bayliss-Smith is one of four TIF trustees and Michael Hands is Director. Since 2007 this foundation has raised funds of over £K 175 for its own activities and to support local NGOs in Honduras that are involved in promoting Inga-based alley cropping systems to small farmers. Current donors include private individuals, Strategic Funding Group of The Funding Network, and Innocent Drinks Foundation. TIF now has available committed funds of over £70K per year to support activities over the next three years.

2. Impacts in Honduras:

  • Many decision makers and professionals in both government and NGOs have adopted Inga-based agroforestry for conservation management in the buffer zones of forest protected areas.
  • At San Marcos in the Cuero valley of Honduras a 7-hectare demonstration farm was purchased by Inga Foundation in 2011 to promote sustainable alley-cropping in the region;
  • The farm will include a seed nursery capable of producing in the near future about 100,000 bag-grown saplings of Inga edulis and I. oerstediana for sale (at nominal price) to local farmers.
  • As a direct result of these efforts, Inga-based agroforestry has so far been adopted by about 40 families in this region, with ongoing work among another 200 families that are being trained as potential adopters. Adoption has also been reported in Guatemala.

3. A documentary film, ‘Up in Smoke’ has been made by Adam Wakeling. It was premiered at the Sheffield Documentary Festival in June 2011 and screened by Channel 4 Television in September 2011. This film won the Objectif d’Argent award in the Development category of the Brussels Millennium Film Festival, April 2012, and is being screened on television worldwide. It outlines the scientific work initiated by the Geography Department, University of Cambridge. It highlights the applied research of Michael Hands and The Inga Foundation, and then traces the impact in Honduras on the livelihoods of campesinos who are in the process of adopting Inga-based alley-cropping.

Guama model Inga Foundation advert

Meanwhile experimental work by Martin Kaonga in Zambia yielded data for his Ph.D on the nutrient cycle in various agroforestry systems in savanna climates. Subsequent laboratory work and modelling has generated data on the carbon cycle that are relevant for our understanding of carbon sequestration under various types of land use.


  • Kaonga, M.L. and T.P. Bayliss-Smith (2012) Simulation of carbon pool changes in woodlots in eastern Zambia using ther CO2FIX model. Agroforestry Systems 86: 213-223.
  • Kaonga, M.L. and T.P. Bayliss-Smith (2012) ‘A conceptual model of carbon dynamics for improved fallows in the tropics’. In- M.L. Kaonga, ed. Agroforestry for Diversity and Ecosystem Services — Science and Practice. Intech Open Access Publisher, <>, 23-44.
  • Kaonga, M. and T. Bayliss-Smith (2010) ‘Allometric models for estimation of aboveground carbon stocks in improved fallows in eastern Zambia’. Agroforestry Systems 78: 217-232.
  • Kaonga, M. and T. Bayliss-Smith (2009) ‘Carbon pools in tree biomass and the soil in improved fallows in eastern Zambia’. Agroforestry Systems 76: 37-51.
  • Hands, M. R. (2004) ‘El uso de Inga en Cultivo en Callejones; una alternativa sostenible comprobada a la agricultura migratoria en el Bosque Lluvioso’. In- Cordero, J. and Boshier, D. H. (eds.), Árboles de Centroamérica: Un Manual para Extensionistas. Oxford Forestry Institute and CATIE, Costa Rica. OFI, Oxford, 601-606.
  • Bayliss-Smith, T.P. (2003) ‘Livelihoods and sustainability at the agrarian frontier’. Geografiska Annaler B, 85(1), 63-65.
  • Hviding, E. and T.P. Bayliss-Smith (2000) Islands of Rainforest: Agroforestry, Logging and Ecotourism in Solomon Islands. Ashgate, Aldershot. 371 pp.
  • Adomako, E.E., J.K. Adomako and T.P. Bayliss-Smith (1998) ‘Conservation by tradition: the case of the Guako sacred grove’. In- D.S. Amlalo, L.D. Atsiatorme and C. Fiati (eds.) Biodiversity conservation: traditional knowledge and modern concepts. Proceedings of the Third UNESCO MAB Regional Seminar, Cape Coast, 9-12 March 1997. Environmental Protection Agency, Accra, Ghana, 7-15.
  • Hands, M.R. (1998) The uses of Inga in the acid soils of the rainforest zone: Alley-cropping sustainability and soil-regeneration’. In- Pennington, T.D. and Fernandes, E.C.M. (eds.) The Genus Inga: Utilization The Royal Botanic Gardens, Kew, 53-86.
  • Bayliss-Smith, T.P. (1996) ‘La adopción del “cultivo en callejones” por cultivadores en el bosque húmedo tropical: Entre el entusiasmo desaforado y la prudente cautela?’ Opción Amazónica. Ciencia, Technologia y Cultura 1 (1): 9-21.
  • Bayliss-Smith, T.P., B.W. Bache and M.R. Hands (1995) ‘Phosphorus cycling and sustainability in agroforestry systems in the humid tropics’ In- S. Risopoulos (ed.) Deuxieme programme. Science et Technique au service du Développement/ Second programme, Science and Technology for Development, Projets de recherche/ Research projects 1987-1991, vol. 2. Technical Centre for Agricultural and Rural Co-operation, Wageningen, Netherlands, for D.G. XII, European Commission, Brussels, 11-16.
  • Hands, M.R., A.F. Harrison and T.P. Bayliss-Smith (1995) ‘Phosphorus dynamics in slash-and-burn and alley-cropping systems of the humid tropics’. In- H. Tiessen (ed.) Phosphorus in the Global Environment: Transfers, Cycles and Management. SCOPE Report 54, J. Wiley, Chichester, 155-170.