A decline in pollinator dependent vegetable crop productivity in India indicates pollination limitation and consequent agro-economic crises.

Abstract

Approximately 70% of the tropical crop species depend on pollinators for optimum yields (Roubik, 1995, Klein 2007). The economic value of such pollinated crops to India is $726 million and India is the world's second largest vegetable producer (Sidhu, 2005). This status has been underpinned by large-scale changes in land-use and pesticide dependency (Fazal, 2000; Shaw & Satish, 2007). A method (c.f. Aizen et al. 2008) that partitions crops into categories depending on their relative pollinator dependence (Index of pollinator dependence, DI) was applied to analysis of vegetable yields for India over 45 years (1963-2008) using FAO data. This has revealed that since 1993, relative yields of crop production has either flattened or declined, while pollinator non dependent crops show no similar decline. This pattern of yield limitation may be due to several factors, among which pollinator limitation would be a major factor (Kearns et al. 1998) and this risk is discussed. Pollinator decline will have serious socio-economic consequences for countries like India, which host a large population of small and marginal farms for whom falling yield level would be critical for subsistence (Kearns et al. 1998; Kremen et al., 2002; Klein et al., 2007; Potts et al., 2010). We show here for the first time any indication of pollination limitation in India, an emerging economy that is still predominantly agrarian. Detailed land use and ecological surveys are urgently required to assess the ecology of pollinating insects within and around agricultural systems in India.