Unintended habitat loss on private land from grazing restrictions on public rangelands

摘要

1.Management of public lands,and who should have access to them,is often contentious.Most ranches in the western US rely upon seasonal grazing access to public lands,and conflict over biodiversity management has led to proposals to restrict grazing access on public lands.We evaluate whether grazing restrictions on public rangelands could have the unintended effect of increasing the conversion of private rangeland to cropland,causing habitat loss for sage-grouse,a species of conservation concern.2.Using a model parameterized with empirical observations of land use change and ranch versus cropland profitability,we explore how changes to public lands grazing policy could affect ranch profitability and consequently land use on private lands across the western US.3.We predict that restricting grazing of public lands by 50% would result in the loss of an additional 171,400 ha of sage-grouse habitat on private lands by 2050,on top of the 842,000 ha predicted to be lost under business as usual.Most of this conversion would affect sage-grouse mesic habitat,75% of which occurs on private land and is vital to the species during brood rearing.Under such policy changes,we estimate that an additional 105,700 ha (3.24%) of sage-grouse mesic habitat held on private land in the study region would be directly lost by 2050,and the cumulative area affected by fragmentation would be much higher.4.By considering the human and ecological links between public and private land,we show that attempts to improve habitat on public lands via grazing restrictions could result in greater system-wide fragmentation of sage-grouse habitat from unintended habitat loss on private lands.5.Synthesis and applications.Policy interventions on public lands can affect private landholders.Landholder? responses can result in unintended consequences,both for habitat on private land and community support for conservation.Restricting grazing on US public lands is likely to increase habitat loss on private lands an