The average distance to a forest is increasing for Americans

In a decade it has increased by 14 percent, or about a third of a mile.

The loss of isolated forest patches has seen forests move farther on average from any given point in the continental US. In a new PLOS ONE study, Giorgos Mountrakis and colleagues looked at data from 1990 to 2000 and found that the shifting distance was more pronounced in rural areas than in urban settings, as they are at higher risk of losing forested patches.

We spoke with Mountrakis of the College of Environmental Science and Forestry at the State University of New York about the work.

ResearchGate: What does the measurement average forest distance indicate?

Giorgos Mountrakis: It indicates how far the nearest forest is from a given location, in our case any location within the continental US. We used this metric as an indicator of forest quality under the assumption that spatially unique forests may perform additional key services as opposed to larger continuous forest patches.

RG: How has it changed?

Mountrakis: For the continental US, the average distance was 3674m in 1992 and increased by 514m, or 14 percent, in 2001.

RG: What time period did you look at? Why this period?

Mountrakis: We looked into changes from early 90s to early 2000s. This was partially driven by satellite-derived maps available during that period that allowed a consistent comparison across the two times.

RG: Are there areas that suffered more than others?

Mountrakis: Yes, our results indicate that forest attrition is considerably higher in the western United States, in rural areas, and in public lands.

RG: What environmental impact do these forest patches have?

Mountrakis: You can think of these isolated forest patches as small but key environmental sanctuaries for biodiversity. They provide essential habitat and their loss could result in severe decline of population sizes and species richness. These declines do not only affect that particular area but also adjacent locations, as these isolated patches often act as transportation islands for migratory species, similarly to an oasis in the desert.

RG: How did you determine these changes?

Mountrakis: The changes were determined by analyzing satellite-derived maps depicting land cover and associated changes. These maps were fed in specialized geostatistical software where we calculated the observed distance change. We also looked whether these losses were randomly distributed or penalized more isolated forest patches, which they did.

RG: What’s the cause of these forest losses?

Mountrakis: While our study did not focus on the drivers, typical causes are urbanization, agricultural expansion, logging, and fires.

RG: What should people take from your study?

Mountrakis: Not all forest is equal. Our work scratched the surface of using geographic analysis and satellite data to establish a national policy of prioritization of forest conservation efforts. Typical large intact forests receive the majority of attention but in some cases smaller isolated forest patches, that are under a larger threat and are of equal importance, are left behind. We would like to thank the National Urban and Community Forestry Advisory Council and the McIntire Stennis program, US Forest Service for supporting this work.

Featured image courtesy of Trey Ratcliff.