Forecasted greater sage-grouse conservation using novel mitigation

A common Intermountain West US land management challenge is the
conservation of declining greater sage-grouse (GSG) populations amid
development pressures in sagebrush shrublands on public lands.
High-quality compensatory mitigation (or “offsets”) is an important tool
for conservation where impacts are not otherwise being avoided, such as in
mine development. We tested whether a compensatory mitigation bank for GSG
coupled with public lands policy innovations was feasible in arid
shrublands with decadal succession and high failure rates for seedings.
Vegetation change and the associated change of GSG per-capita population
growth rate (λ) due to proposed vegetation treatments were modelled on a
218,049-ha central Nevada landscape. Using remote-sensed vegetation
rasters and spatial state-and-transition simulation models (STSM) coupled
with a demographic GSG model, we compared the effects of proposed
vegetation treatments (uplift scenario) to baseline (control) actions on a
net gain of λ in sagebrush shrublands and wet meadows across public and
private lands. Dominant treatments separated into thinning conifers
encroaching shrublands and seeding in shrublands dominated by non-native
annual species after past fires. Smaller treatments were used in wet
meadows, which are critical GSG late-brood rearing vegetation. The primary
data components were, therefore, vegetation remote sensing, spatial
state-and-transition simulation models with many input raster that provide
initial conditions and spatial constraints imposed on natural and
management-caused disturbances, and a greater sage-grouse demographic
habitat suitability model with its associated input rasters and lookup
tables. The landscape-wide average λ was 0.74230 at the project’s onset in
2014. The average λ between scenarios was 0.71653 and 0.72289,
respectively, for the baseline and uplift scenarios after 35 years of
simulations. The significant λ differences between scenarios and
innovative science and policies enabled the parties of the mitigation bank
to consider future credit releases based on implemented and monitored
aridland restoration actions conducted on private and public aridlands.