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Trophic Interaction Networks and Ecosystem Services

Trophic Interaction Networks and Ecosystem Services

Chapter:
(p.49) Chapter Three Trophic Interaction Networks and Ecosystem Services
Source:
Why Birds Matter
Author(s):
Christopher J. WhelanDiana F. TombackDave KellyMatthew D. Johnson
Publisher:
University of Chicago Press
DOI:10.7208/chicago/9780226382777.003.0003

Birds function within their ecosystems in ways that include many direct and indirect chains of trophic interaction. In some interaction chains, birds exert top-down effects in “trophic cascades.” These occur when a predatory species directly reduces its prey abundance and consequently indirectly releases suppression of species at lower trophic levels. Many bird species initiate trophic cascades in terrestrial and aquatic ecosystems, and in natural and agro-ecosystems. Services provided by birds through trophic cascades benefit humans primarily through pest control in natural forests, forestry plantations, fruit orchards, and a variety of crop-based agro-ecosystems. Cascade strength may be affected by predator prey specificity, redundancy, species diversity, and productivity. Some birds influence ecosystem function both through either bottom up interactions or through intermediate trophic positions within interaction networks. These effects can also reverberate through trophic webs. Global change, including anthropogenic perturbation, may lead to a loss of ecosystem services, including seed dispersal and pollination services by birds. These losses may cause declines keystone or foundation plant species, resulting in losses in biodiversity and ecosystem integrity. We conclude with suggestions for future research needs on bird ecosystem services, particularly in light of global change.

Keywords:   agroecosystems, bottom-up interactions, foundation species, pest control, top-down interaction, trophic cascade, trophic interaction networks

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