Terrestrial food webs based on living plants may well represent 75% of global terrestrial biodiversity.
The majority of component species are specialists and a large proportion is parasitic as herbivores
and carnivores, with consequences for high sensitivity to heterogeneity on a variety of scales.
Relatively large primary producers support relatively small insect herbivores and carnivores, with
plants providing both food and habitat, making resource-driven effects very strong. Complexity of
resources provided by plants, with influences up the food web, is generated by at least seven major
factors: (i) plants as food; (ii) plants as habitat; (iii) the physical traits of plants such as size, toughness
and trichomes; (iv) traits of plants that require evolutionary responses by herbivores in terms
of crypsis, phenological synchrony, life history and behavioral adaptations; (v) the constitutive
chemicals in plants; (vi) the induced changes in plants caused by herbivory; and (vii) landscape and
biogeographic variation in vegetation types and food web richness. No other trophic level has such
a wide-ranging impact on other trophic levels. But such broad impact makes the term ‘food web’
overly narrow and inadequate. The term ‘interaction web’ is preferable, aiding recognition of the
many kinds of interactions that pass up food webs from living plants. Any claim that top-down
impact is stronger than bottom-up influences is necessarily couched in a narrow sense of biomass or
numbers reduction.