This is the old United Nations University website. Visit the new site at

Return to the PLEC Pages

About PLEC - an Introduction
People, Land Management and Environmental Change (PLEC)

In response to a strong demand for models of biodiversity management in agricultural ecosystems, PLEC aims to identify, test and promote locally developed management practices that:

  • combine traditional knowledge and approaches with new knowledge and technologies;
  • embrace ecosystem functions and processes for enhancing livelihoods, principally through optimal degree of structural, spatial, temporal, trophic, species and genetic diversity.

The project involves local farmers and scientists in setting up demonstration sites in critical ecosystems and areas of globally significant biodiversity, such as forest, mountain, semi-arid, freshwater, and wetland in major regions in Africa, Asia and the Pacific, and the tropical America.

The PLEC network uniquely provides for South-to-South cooperation and South-to-North twinning arrangements. The project is organized into a network of locally based clusters and representatively diverse regions that have been established in Africa (Ghana, Guinea, Kenya, Tanzania, Uganda), Asia-Pacific (China, Thailand, Papua New Guinea), and Latin America (Brazil, Jamaica, Peru, Mexico) with participation of scientists from the North (currently United States, Japan, Australia, Britain). Each cluster is multidisciplinary, based in a national organization in collaboration with several institutions.

The UNU Project on People, Land Management and Environmental Change (PLEC) was renamed as People, Land Management and Ecosystem Conservation late 2002.

The "Agrodiversity" Concept

Agrodiversity is the many ways in which farmers use the natural diversity of the environment for livelihoods, including their choice of crops and animals but also their management of land, water and biota as a whole. It broadens the concept of agricultural biodiversity from meaning simply genetic resources to meaning the landscape level biodiversity and the diversity of local social organizations and technologies that support biodiversity and reduce agricultural and ecological risks. The agrodiversity covers four elements, i.e. biophysical diversity, management diversity, agrobiodiversity and organizational diversity (see Table 1), as well as multiple interactions of these elements.

Table 1 Four elements of agrodiversity

Agrodiversity categories Description
Biophysical diversity The diversity of the natural environment including the intrinsic quality of the natural resource base that is used for production. It includes the natural resilience of the biophysical environment; soil characteristics, plant life, other biota. It takes in physical and chemical aspects of the soil, hydrology, climate, and the variability and variation in all these elements.
Management diversity All methods of managing the land, water and biota for crop and livestock production, and the maintenance of soil fertility and structure. Included are biological, chemical and physical methods of management.
Agro-biodiversity This is all species and varieties used by or useful to people, with a particular emphasis on crop, plant and animal combinations. It may include biota that are indirectly useful, and emphasizes the manner in which they are used to sustain or increase production, reduce risk and enhance conservation.
Organizational diversity This is the diversity in the manner in which farms are operated, owned and managed, and the use of resource endowments from different sources. Explanatory elements include labor, household size, capital assets, reliance on off-farm employment, and so on.

Working Guidelines

PLEC seeks to build on "agrodiversity" for viable diversity management approaches toward improvement of rural livelihoods, especially in the marginal areas. Key components of the PLEC methodology are 1) Demonstration site, 2) Assessment of agrodiversity and its component, and 3) Promotion of agrodiversity through "Farmer learning from expert farmer".

Demonstration sites are not so much physical places, but people-centred processes, and partnership between scientists, real farmers, local communities and other stakeholders searching for sustainability on the ground.

The project starts with understanding and assessment of production and conservation practices in productive landscapes. The assessment stratifies landscapes into land use stages for recording spatial as well as temporal diversity. The assessment further stratifies the landscapes into individual family landholdings for detecting the difference in biodiversity and its management between families, as well as spotting expert farmers and their exceptional practices in the communities.

Farmers obtain new ideas and technologies often through exchanges and observation with other farmers, and prefer to see concrete results. Improvement in practice is built on the best of current practice, and not engineered externally. PLEC incorporates the "expert farmers" - developers of innovative practices and their communities into rural research, demonstration, and outreach.

PLEC working guidelines and case studies on agrodiversity are introduced in three major publications:

  • Cultivating Biodiversity: the Understanding, Analysis and Use of Agrodiversity (Brookfield, et al. eds. 2002)
  • Handbook for the Field Assessment of Land Degradation" (Stocking, et al. eds. 2001, available online)
  • PLEC Agrodiversity Database Manual (Coffey, 2000, available online).
  • Special Issue on Methodology, PLEC News and Views, No. 13, April 1999, available online.


PLEC was part of the Global Environment Facility (GEF) work programme during 1998-2002 with UNU as the Executing Agency and the United Nations Environment Programme (UNEP) as the Implementing Agency. Final evaluation report is available online. The project experience is summarized in the book "Agrodiversity: Learning from Farmers across the World" (Brookfield, et al. eds. 2003).

PLEC is now focused on mainstreaming lessons learned into national and international policies and training institutions.

Return to the main PLEC Pages

      PLEC Contact: Luohui Liang -
      Web Contact: