Effects of plant invasions on wildlife in desert grasslands

Like all grasslands across North America, the distribution of desert grasslands has been reduced markedly, and remnants have been altered extensively by humans. In Arizona, New Mexico, Texas, USA, and in Mexico, desert grasslands have been invaded by dozens of non-native plants, especially perennial grasses that evolved in arid systems with similar climate and disturbance regimes. In desert grasslands invaded by non-native plants, biomass, richness, and diversity of native plants typically decrease, whereas plant density, biomass, and litter typically increase. These changes in composition and structure of the plant community affect animals that inhabit grassland ecosystems, with the direction and magnitude of effects reflecting the resource needs of each species, the degree of plant invasion, and the contrast in structure between invading and native plants. When non-native plants present similar structural cues but provide different levels of resources than native plants, cues that trigger habitat selection by animals may be decoupled from the resources linked evolutionarily to that cue, creating the potential for an ecological trap. Plant invasions also influence the ecological drivers that maintain grasslands in an open condition, which will alter the long-term dynamics of plant and animal populations. Specifically, by increasing fuel load and continuity, fires in invaded grasslands increase in frequency and intensity relative to those in native grasslands. Although eradication is unlikely once a non-native plant has naturalized, retaining patches of native vegetation within a matrix of non-native plants may provide a strategy to reduce effects of plant invasions on wildlife in grasslands.