forest attrition deforestation saw

Forest attrition distance reveals: deforestation was considerably higher in the western U.S.

The U.S. forests have been affected by dramatic land cover change over the past few centuries. In a paper published in PLoS One one month ago, Dr. Mountrakis and Sheng Yang, a graduate student, tried slicing deforestation a different way. Read more about a new way to measure deforestation, i.e. forest attrition distance, and and where in the U.S. it  was higher!


Forests are a critical natural resource serving multiple purposes and a wide range of stakeholders. Over 30% of the conterminous U.S. is covered by forestlands. However, the forest cover in U.S. was much higher than that.

READ ALSO: Optimal level of deforestation

Chris Roddick, chief arborist at the Brooklyn Botanic Garden in New York explained:

“It’s said that squirrels could travel from tree to tree from the Northeast to the Mississippi without ever having to touch the ground. In the old growth forests in the Northeast, you had hemlock that were six or seven feet in diameter, chestnut trees 200 feet tall.”

Since then, agriculture, logging, urban development and other human activities have thinned or wiped out these once-lush forests.

READ ALSO: Illegal logging costs between 30 and 100 billion USD annualy

Native Americans used to burn forests to farm, but such practices were nowhere as close to “the drastic deforestation that came with the Europeans”, Riddick added.

How to measure deforestation?

One of the most common ways to estimate the extent of deforestation is to simply measure the total amount of forest cover lost. However, Giorgios Mountrakis, an associate professor at the State University of New York College of Environmental Science and Forestry noticed that not all deforestation is created equal.

READ ALSO: How decentralized policies can help to reduce deforestation?

Therefore, together with his graduate student tried slicing deforestation a different way. By the use of satellite maps, they calculated the average distance to the nearest forest from any point in the continental United States in 1992 versus 2001. This newly created metric has been named  by the researchers as “forest attrition distance”.

What forest attrition distance (FAD) really measure?

This indicator measure the removal of isolated forest patches. In other words, when these patches are lost, adjacent forests become farther apart, and potentially can affect, among others, soil erosion, biodiversity, microclimate and other conditions.

Results

Researchers found, that at the national level the total forest cover loss was approximately 90,400 km2 (34,900 square miles), approximately the size of the state of Maine, and constituted a relative change of -2.96%. Examining the spatial arrangement of this change the average FAD was 3674m in 1992 and increased by 514m or 13.99% in 2001.

the highest forest attrition is concentrated in western U.S.
While the southeastern U.S. is experiencing high forest loss, the highest forest attrition is concentrated in other parts of the country. Source: Yang and Mountrakis (2017).

Dr. Mountrakis says he believes that the new metric “goes beyond forest quantity”, and it gives a glimpse into forest quality. Moreover he added:

“Isolated forest patches can have a very specific importance for biodiversity. As birds migrate from one location to another, for instance, they can use these isolated forests as pit stops. You can think of them as oases in a desert.”

Eastern vs. Western U.S. – where the FAD was higher?

According to scientists, it was found that forest attrition seemed to be higher in the western United States, in rural areas and on public lands. However, scientists noted that they need to expand their research, in order to better understand those trends.

forest attrition visualized in four ecoregions.
Forest attrition visualized in four ecoregions. Forest losses during the 1990s are depicted as red pixels, forest present in 2000 is shown as green pixels and non-forest is shown as gray pixels. Forest attrition is considerably higher in western ecoregions than in eastern ecoregions as forest losses occurred more frequently in gap regions. Source: Yang and Mountrakis (2017).

Source: Yang S, Mountrakis G. 2017. Forest dynamics in the U.S. indicate disproportionate attrition in western forests, rural areas and public lands. PLoS ONE 12(2): e0171383.

Photo credit: Rafal Chudy

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