Ecologists and farmers often have contrasting perceptions about the value of natural habitat in agricultural production landscapes, which so far has been little acknowledged in ecology and conservation. Ecologists and conservationists often appreciate the contribution of natural habitat to biodiversity and potential ecosystem services such as biological pest control, whereas many farmers see habitat remnants as a waste of cropland or source of pests. While natural habitat has been shown to increase pest control in many systems, we here identify five hypotheses for when and why natural habitat can fail to support biological pest control, and illustrate each with case studies from the literature: (1) pest populations have no effective natural enemies in the region, (2) natural habitat is a greater source of pests than natural enemies, (3) crops provide more resources for natural enemies than does natural habitat, (4) natural habitat is insufficient in amount, proximity, composition, or configuration to provide large enough enemy populations needed for pest control, and (5) agricultural practices counteract enemy establishment and biocontrol provided by natural habitat. In conclusion, we show that the relative importance of natural habitat for biocontrol can vary dramatically depending on type of crop, pest, predator, land management, and landscape structure. This variation needs to be considered when designing measures aimed at enhancing biocontrol services through restoring or maintaining natural habitat.
Bibliographical noteFunding Information:
We are grateful for many helpful comments by three anonymous reviewers. Author sequence follows the “sequence-determines-credit” (from TT to RCK) and the “equal-contribution” norm (from PB to WZ) (see Tscharntke et al., 2007b ). This work benefited from support from the National Socio-Environmental Synthesis Center (SESYNC) - NSF award DBI-1052875 for the project “Evidence and Decision-Support Tools for Controlling Agricultural Pests with Conservation Interventions” organized by Daniel Karp and Becky Chaplin-Kramer. TT acknowledges support by the DFG-CRC 990 EFForTS and the DFG-FOR 2432 , TT and PB by the Biodiversa project FarmLand , DK by a Killam Postdoctoral Fellowship, and MJ by the Biodiversa project APPEAL . CG was supported in part by the US DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-FC02-07ER64494 ), the US DOE OBP Office of Energy and Renewable Energy ( DE-AC05-76RL01830 ), and by the USDA NIFA Agriculture and Food Research Initiative ( 2011-67009-30022 ). AR acknowledges support by the Era-net project MULTAGRI ( EU/FP7 ), NAS by the Julius Career Award and the Cotton Research & Development Corporation , FDC and WZ by CGIAR's Water, Land and Ecosystems (WLE) research program, AL by the EPA Science to Achieve Results Fellowship (FP 91762601), and EAM by the EU/FP7 project LIBERATION ( 311781 ).
- Agricultural management
- Ecosystem services
- Landscape structure
- Natural enemies
- Pest regulation