BABE · Why is the world green: testing top-down control of plant-herbivore food webs by experiments with birds, bats and ants

Why is the world green? Because predators control herbivores, allowing plants to flourish. This >50 years old answer to the deceptively simple question remains controversial. After all, plants are also protected from herbivores physically and by secondary chemistry. My goal is to test novel aspects of the “green world hypothesis”: ● How the importance of top-down effects varies with forest diversity and productivity along a latitudinal gradient? ● How the key predators, birds, bats and ants, contribute to top-down effects individually and in synergy? I strive to understand this because: ● While there is evidence that predators reduce herbivore abundance and enhance plant growth, the importance of top-down control is poorly understood across a range of forests. ● The importance of key predatory groups, and their antagonistic and synergic interactions, have been rarely studied, despite their potential impact on ecosystem dynamics in changing world. I wish to achieve my goals by: ● Factorial manipulations of key insectivorous predators (birds, bats, ants) to measure their effects on lower trophic levels in forest understories and canopies, accessed by canopy cranes, along latitudinal gradient spanning 75o from Australia to Japan. ● Studying compensatory effects among predatory taxa on herbivore and plant performance. Why this has not been done before: ● Factorial experimental exclusion of predatory groups replicated on a large spatial scale is logistically difficult. ● Canopy crane network along a latitudinal gradient has only recently become available. I am in excellent position to succeed as I have experience with ● foodweb experiments along an elevation gradient in New Guinea rainforests, ● study of bird, bat and arthropod communities. If the project is successful, it will: ● Allow understanding the importance of predators from temperate to tropical forests. ● Establish a network of experimental sites along a network of canopy cranes open for follow-up research.