An assessment of ecological diversity in homegardens: A case study from Kerala State, India

Homegardens are unique agroforestry systems that provide economic and sociocultural benefits to the tropical subsistence farmer. These intensively managed systems are often the only source of nutrition and income for the household. Along with their economic value, these gardens are also known for their high levels of biological diversity. This study attempted to quantify these patterns of diversity by inventorying 75 homegardens in Thrissur district in Kerala, India. The utility values of plant species were classified as primary, secondary, or tertiary based on farmer responses to survey questions. Sorenson's Index of similarity indicated fairly high levels of similarity in species composition across inventoried gardens, indicating some common use patterns among farmers. The Shannon-Wiener index and Margalef index were both calculated in order to ascertain levels of biological diversity in these managed agricultural systems. The Shannon-Wiener index indicated patterns comparable with natural forested regions in the area, while the Margalef index indicated species richness levels that were only slightly lower than those for forests in the Western Ghats. Agroecological importance value indices (IVI) were calculated and nine crop categories were identified as most important. Vegetables, ornamentals, and medicinal plants were found to be extremely important across all size categories of gardens. A multivariate regression analysis indicated that although economic value of homegardens increased with years in cultivation and land size, it reduced with increase in species richness.