Data from: Consumer control as a common driver of coastal vegetation worldwide

Rapid, global anthropogenic alteration of food webs in ecosystems
necessitates a better understanding of how consumers regulate natural
communities. We provide a global synthesis of consumer control of
vegetation in coastal wetlands, where the domineering role of physical
factors such as nutrient and salinity, rather than consumers, has been
emphasized for decades. Using a dataset of 1748 measures of consumer
effects reported in 443 experiments/observations on all continents except
the Antarctica, we examine the generality of consumer control in salt
marshes and mangroves globally. Our analyses show that salt marsh
herbivores, including insects, snails, crabs, waterfowl, small mammals,
and livestock, generally and often strongly suppress plant survival,
aboveground biomass, and height, while their effects on plant density,
belowground biomass, reproduction, and cover are more variable. These
effects occur in forbs, grasses, and shrubs, and in both seedlings and
adult plants. Herbivores additionally affect plant nutrient stoichiometry,
and mediate plant interactions, though their effects on plant diversity
are less consistent. Higher trophic levels also affect plants, as
predators facilitate plant growth through trophic cascades that suppress
grazer abundance and grazing rate. In mangroves, there are also signs of
consumer control, though the relatively few studies available have often
focused on mangrove propagules and seedlings rather than adults. Our
analyses further reveal that the strength of consumer control is regulated
by many physical factors. Nutrient, disturbance, and flooding, for
example, amplify the negative effects of herbivores. Along latitudinal
gradients, increased temperature enhances the negative effects of
ectothermic herbivores, but has no effect on those of endothermic
herbivores. Consumer control of coastal plants is also apparent across
study methodologies: in field and laboratory settings, in observational
studies, in consumer exclusion and addition experiments, in natural and
transplanted plants, and in experiments of various durations. The role of
consumer control in coastal vegetation worldwide highlights the need to
better recognize and theoretically conceptualize both top-down and
bottom-up forcing and their interactions in coastal wetlands. Improved
understanding and conservation of coastal wetlands will only occur if we
incorporate what the science has revealed: trophic feedbacks are an
important and pervasive determinant of coastal plant communities.