Does agricultural intensification impact pest regulation service by frogs in a natural multi-trophic system?

Abstract

Agricultural intensification is a major driver of biodiversity loss. However, the exact impacts of such loss of key ecosystem service (ES) provisions in agriculture require more scrutiny. We assessed the population loss impacts of a key ES-providing species in an agricultural landscape. We tested the hypothesis that intensive agriculture causes density reduction of frogs known as pest regulators and that negatively affects pest regulation. Different frog densities (high and low) observed in a previous study in low and high agricultural intensification areas were used as treatments in a semi-controlled field experiment. Functional response of the frog species was also studied. Neither high nor low frog density had any significant effect on respective pest populations. Limited feeding rate of the frog species might have contributed to reduced predation pressure on pests. Surprisingly, at low density, frogs significantly reduced the arthropod natural enemies, probably their preferred prey due to the latter’s agility. Unlike in low frog density treatment, increased intraspecific competition at high frog density made them seek out pests as alternative prey to the preferred arthropod pest enemies, whose populations were not affected by frog density. This study for the first time links the population loss of frogs, a potential bio-control agent to ES provision in a multi-trophic system.