Pollination services decline with distance from natural habitat even in biodiversity‐rich areas

Abstract

Summary1. There is considerable evidence for the negative impacts of habitat alteration on pollinators in highly disturbed regions of the world. However, it remains unclear whether these findings reflect a global crisis for crop pollination. Understanding the extent to which world agriculture is endangered by pollinator decline is essential if the economic valuation of nature is to be used to promote conservation. 2. We assess the susceptibility to pollinator limitation of one of the most important tropical and subtropical fruit crops, mango Mangifera indica L., commonly planted in a region of South Africa located between two large biodiversity-rich protected natural areas. We conducted flower visitor surveys, exclusion experiments and spatial analysis of flower visitation and fruit production patterns. 3. Our results show that both ants and flower visitors were effective pollinators of mango, the latter significantly declining (in abundance and species richness) with distance to natural habitat while ants were not affected. Neither the absence of pesticides nor the supplementation of flower visitors by using managed honeybees served to offset these negative impacts. Food-web data suggest that maintaining diversity of flower resources within farmland can help maintain pollinator communities. 4. Moreover, models based exclusively on pollinator abundance underestimated the negative effect of distance from natural habitat on production (42% less at 500 m from natural habitat). As soil nutrient levels and water content are regularly measured and corrected in all study sites, these results suggest that pollinator diversity may also be important. 5. Synthesis and applications. This study provides one of the first examples of marked pollination limitation in farms surrounded by well-protected natural habitat. For mango farming to be sustainable, it is essential to limit contiguous growth of farmland and consider practices that restore the complexity of plant-pollinator networks within farms, for example through the creation and maintenance of pollinator-friendly areas. By highlighting the economic gains of adopting pollinator-friendly practices in agriculture, this work contributes to a growing body of studies that reveal that making farmland more suitable for pollinators benefits both agriculture and nature conservation.

Ecosystem Services in Biologically Diversified versus Conventional Farming Systems: Benefits, Externalities, and Trade-Offs

“…There are still relatively few studies, however, that have measured the effects of local-scale management actions on pollination services. In those studies that do, landscape-scale variables overshadow the effects of local-scale management (e.g., Kremen et al 2002, Carvalheiro et al 2010. Thus there is a need for additional highly replicated studies that examine both local and landscape factors (such as those conducted by Holzschuh et al 2008 andGabriel et al 2010) and that study not only pollinator communities but also pollination services.…”

How natural capital delivers ecosystem services: A typology derived from a systematic review

“…Habitat area is often found to be positively linked to the services of pollination and pest control, and the provision of these services tends to decline as the distance to natural habitat increases (e.g. Carvalheiro et al, 2010;Garibaldi et al, 2011). More diverse habitats support higher abundance and diversity of beneficial species, so vegetation species richness, structural diversity and landscape diversity are correlated with pollination and pest regulation efficiency (e.g.…”

Indirect interactions between crops and natural vegetation through flower visitors: the importance of temporal as well as spatial spillover

“…All flowering plants observed were identified, and the total number of flowers per species per plot recorded. As mango is a hyperabundant flowering species, the total number of flowers was estimated by counting the number of open flowers of three randomly-selected inflorescences (Carvalheiro et al, 2010). The average was multiplied by the total number of inflorescences counted in the plot.…”

“…Previous studies have found that natural vegetation in the area is a source of both flower visitors (Carvalheiro et al, 2010(Carvalheiro et al, , 2012Geslin et al, 2016) and natural enemies of crop pests (Henri et al, 2015;Morgan et al, 2017) in mango fields. Mangos in turn have been shown to harbour pests that can spill over into natural vegetation (Moxley et al, 2017), and it is likely that pollinators, too, spill over into natural vegetation.…”