Retaining biodiversity in intensive farmland: epiphyte removal in oil palm plantations does not affect yield.

Graham W Prescott,David P Edwards,William A Foster

doi:10.1002/ece3.1462

Abstract

The expansion of agriculture into tropical forest frontiers is one of the primary drivers of the global extinction crisis, resulting in calls to intensify tropical agriculture to reduce demand for more forest land and thus spare land for nature. Intensification is likely to reduce habitat complexity, with profound consequences for biodiversity within agricultural landscapes. Understanding which features of habitat complexity are essential for maintaining biodiversity and associated ecosystem services within agricultural landscapes without compromising productivity is therefore key to limiting the environmental damage associated with producing food intensively. Here, we focus on oil palm, a rapidly expanding crop in the tropics and subject to frequent calls for increased intensification. One promoted strategy is to remove epiphytes that cover the trunks of oil palms, and we ask whether this treatment affects either biodiversity or yield. We experimentally tested this by removing epiphytes from four-hectare plots and seeing if the biodiversity and production of fruit bunches 2 months and 16 months later differed from equivalent control plots where epiphytes were left uncut. We found a species-rich and taxonomically diverse epiphyte community of 58 species from 31 families. Epiphyte removal did not affect the production of fresh fruit bunches, or the species richness and community composition of birds and ants, although the impact on other components of biodiversity remains unknown. We conclude that as they do not adversely affect palm oil production, the diverse epiphyte flora should be left uncut. Our results underscore the importance of experimentally determining the effects of habitat complexity on yield before introducing intensive methods with no discernible benefits.

Highlights

With the global population expected to increase by 40%, daily per capita calorie intake increasing by 11%, and a shift to a more meat-heavy diet, it is estimated that food production levels in 2050 will need to be 100% higher than those in 2005–2007 (Tilman et al 2011)
There was little change in species richness and abundance of birds in control or treatment plots between baseline and post-epiphyte removal stages for both short-term and longer-term experiments (Figs 2 and 3, respectively; Table S3; lists of sampled bird and ant species are in Tables S4 and S5, respectively)
If sustainable intensification of tropical agriculture is key to reducing the loss of global biodiversity while increasing food production, we need to clearly identify the effects of different intensification methods on both production and the taxa living within agricultural landscapes

Summary

Introduction

With the global population expected to increase by 40%, daily per capita calorie intake increasing by 11%, and a shift to a more meat-heavy diet, it is estimated that food production levels in 2050 will need to be 100% higher than those in 2005–2007 (Tilman et al 2011). Future pressure to convert natural habitats into cropland to meet these demands is likely to be concentrated in the tropics, where the largest areas of available land, highest projected levels of increase in population and associated food and energy demands, and most favorable climates for many crops and biofuels are located (Laurance et al 2014). Land-sparing farming is one of the mechanisms proposed to limit further expansion of agriculture and biodiversity loss (Green et al 2005). This approach maximizes yield on existing farmland, so that global food demands can be met using a minimal amount of agricultural land, reducing the need to further convert diverse natural habitats (see Phalan et al (2011))

Methods

Results

Conclusion