Available online 19 May 2015
Demographic Changes Drive Woody Plant Cover Trends—An Example from the Great Plains ☆
Abstract
Woody
plant encroachment—the conversion of grasslands to woodlands—continues
to transform rangelands worldwide, yet its causes and consequences
remain poorly understood. Despite this being a coupled human–ecological
phenomenon, research to date has tended toward ecological aspects of the
issue. In this paper, we provide new insight into the long-term
relationships between human demographics and woody plant cover at the
landscape scale. We used time-series aerial imagery and historical
census data to quantify changes in population, land ownership patterns,
and woody cover between 1937 and 2012 in three different settings in
central Texas, USA. Woody cover closely paralleled population in a
semi-urban watershed (R2 = 0.81) and two separate clusters of rural watersheds (R2
= 0.88 and 0.93), despite exhibiting very different directional trends
over time in each setting. Woody cover also closely tracked average farm
size in each rural watershed cluster (R2 = 0.57 and
0.90). These results highlight a tight coupling between demographic
trends and the extent of woody plant cover. Such human factors may
explain a great deal of woody plant cover patterns in other global
rangeland systems with similar historical contexts and serve as a
predictive proxy of landscape trends. Accordingly, policy
recommendations should consider these demographic factors, and future
woody plant encroachment research should explicitly include human
dimensions.
Keywords
- Ashe juniper;
- Historical imagery;
- Land cover change;
- Landowner objectives;
- Population;
- Woody plant encroachment
Copyright © 2015 Published by Elsevier Inc.