Toward an Ecological Framework for Assessing Risk to Vertebrate Populations from Brine and Petroleum Spills at Exploration and Production Sites

Abstract

Brine and petroleum spills may affect terrestrial vertebrates through loss of reproductive habitat or reduced food availability rather than direct toxicity. A proposed ecological framework for evaluating impacts of these spills includes individual-based population models, a site conceptual trophic model, habitat suitability maps, and a stochastic brine spill generator. Simulation results for mammal populations in the Tallgrass Prairie Preserve petroleum exploration and production (E&P) site in Oklahoma are presented. The persistence of simulated American badger (Taxidea taxus) populations decreased with increasing brine spill area. The decline in persistence and average final population size was much steeper in highly fragmented landscapes. The simulated time to extinction for prairie vole (Microtus ochrogaster) populations showed a threshold at 30% habitat loss from spills; above this threshold the time to extinction decreased with increasing spill area. Vole density was sensitive to the interaction of predation and fragmentation, with fragmentation causing population extinction in the presence of predation, yet stabilizing the population in the absence of predation. We anticipate that our results will aid in future development of “exclusion criteria” for leaving unrestored habitat at E&P sites.

Unnatural landscapes in ecology: generating the spatial distribution of brine spills

“…For example, we have used the Poisson-gamma spill model, in combination with a population model, to quantify spill frequency and area thresholds leading to high risk of local extinction for the American badger (Taxidea taxus) (Efroymson et al, 2004;Jager et al, submitted). …”

The spatial extent of contaminants and the landscape scale: An analysis of the wildlife, conservation biology, and population modeling literature

“…Developing a de minimus size criterion through an initially intensive use of such population models would be a valuable exercise. Individual‐based models are being used to investigate habitat loss from hydrocarbon and brine spills at the Tallgrass Prairie Preserve in Northern Oklahoma [15]. A de minimus size criterion is one of the goals of this project.…”

“…When one first considers the impact to populations at a landscape scale, it may seem obvious that such small releases will be unlikely to result in population‐level impacts. For example, although soil invertebrates and small mammals inhabiting the release site may suffer direct mortality, populations of these species over the entire landscape may show little overall impact [15]. Indeed, many states are developing exclusion criteria based on the size of release using just this logic [16,17].…”

The effect of small-size habitat disturbances on population density and time to extinction of the prairie vole

“…Oil exploration and development cause fragmentation of natural environments through the building of roads and aboveground pipelines which represent barriers to smaller species. Oil development activities often lead to the occurrence of oil or brine spills of various sizes [7] which cause long-term damage to the affected habitat sites. These polluted areas are avoided by some species [7].…”

“…Oil development activities often lead to the occurrence of oil or brine spills of various sizes [7] which cause long-term damage to the affected habitat sites. These polluted areas are avoided by some species [7]. This leads to a long-term modification of the habitat geometry that could affect the whole ecosystem by causing extinction of local herbivore populations and subsequently, of their predators.…”