Christine H. Bielski | Geology Reports

USGS2018

The perpetual state of emergency that sacrifices protected areas in a changing climate

A modern challenge for conservation biology is to assess the consequences of policies that adhere to assumptions of stationarity (e.g. historic norms) in an era of global environmental change. Such policies may result in unexpected and surprising levels of mitigation given future climate change trajectories, especially as agriculture looks to protected areas to buffer against production losses during periods of environmental extremes. Here, we conduct a scenario impact assessment to determine the potential impact of climate change scenarios on the rates at which lands enrolled in the Conservation Reserve Program (CRP) lands are authorized for emergency biomass removal. Grassland biomass on CRP lands is authorized for ‘emergency’ harvesting for agricultural use when precipitation for the last four months falls below 40 percent of the normal, or ‘historical’ mean, precipitation for that four-month period. We develop and analyze scenarios under the condition that policy will continue to operate under assumptions of stationarity, thereby authorizing emergency biomass harvesting solely as a function of precipitation departure from historic norms. Model projections show the historical likelihood of authorizing emergency biomass harvesting in any given year in the northern Great Plains was 33.28 ± 0.96%, according to long-term weather records. Emergency biomass harvesting became the norm (>50% of years) in the scenario reflecting continued increases in emissions and a decrease in growing season precipitation, and areas in the Great Plains with higher historical mean annual rainfall were disproportionately affected and experienced a greater increase in emergency biomass removal. Emergency biomass harvesting decreased only in the scenario reflecting rapid reductions in emissions. Our scenario impact analysis indicates that biomass from lands enrolled in the CRP will be used primarily as a buffer for agriculture in an era of climatic change, unless policy guidelines are adapted or climate change projections significantly depart from the current consensus.

Montana, Nebraska, North Dakota, South Dakota, Wyo↗

USGS2017

Regeneration and invasion of cottonwood riparian forest following wildfire

Populus deltoides is considered to be a weak resprouter and highly susceptible to wildfire, but few post-wildfire studies have tracked P. deltoides response and resprouting within the Great Plains of North America. Following a wildfire in southwestern Kansas, U.S.A., we surveyed burned and unburned areas of a cottonwood riparian forest along the Cimarron River that included a major understory invader, tamarisk ( Tamarix ramosissima Ledeb.). We tested the following hypotheses, which are consistent with the current understanding of P. deltoides response to wildfire in the Great Plains: (1) regeneration of P. deltoides will be low in areas burned by the wildfire; (2) the number of dead P. deltoides individuals will be greater in the wildfire than unburned areas; and (3) tamarisk regeneration will be higher than P. deltoides regeneration in the wildfire areas because tamarisk is considered a stronger resprouter. We found evidence contrary to two of our hypotheses 3 years following the wildfire. (1) P. deltoides regeneration was high following the wildfire, averaging 692 individuals/ha. (2) The number of dead mature cottonwood trees was greater in wildfire plots than in unburned plots. (3) There was more P. deltoides regeneration than tamarisk regeneration following wildfire. These findings, which diverge from the majority of studies examining P. deltoides regeneration in the Great Plains, suggest that differing local environmental and forest stand conditions, coupled with the timing and intensity of the fire, could be important determinants of riparian forest species' responses to wildfire.

Kansas↗