Monitoring population trends of threatened species requires standardized techniques that can be applied over broad areas and repeated through time. Sun bears Helarctos malayanus are a forest dependent tropical bear found throughout most of Southeast Asia. Previous estimates of global population trends have relied on expert opinion and cannot be systematically replicated. We combined data from 1...

The tree and tour cover problems on an edge-weighted graph are to compute a minimum weight tree and closed walk, respectively, whose vertices form a vertex cover. Both problems are NP-hard. In this note we give strongly polynomial time, constant factor approximation algorithms for both problems. An interesting feature of our algorithms is how they combine approximations of other problems, namel...

Reproducing the tree cover changes throughout the Holocene is a challenge for land surface–atmosphere models. Here, results of a transient Holocene simulation of the coupled climate–carbon cycle model, CLIMBER2-LPJ, driven by changes in orbital forcing, are compared with pollen data and pollenbased reconstructions for several regions of Eurasia in terms of changes in tree fraction. The decline ...

Monitoring land cover changes from the 1970s in West Africa is important for assessing the dynamics between land cover types and understanding the anthropogenic impact during this period. Given the lack of historical land cover maps over such a large area, Landsat data is a reliable and consistent source of information on land cover dynamics from the 1970s. This study examines land cover change...

Given an edge-weighted rooted tree T and a positive integer p ( n), where n is the number of vertices in T , we cover all vertices in T by a set of p subtrees each of which contains the root r of T . The minmax rooted-tree cover problem asks to find such a set of p subtrees so as to minimize the maximum weight of the subtrees in the set. In this paper, we propose an O(n) time (2 + ε)-approximat...

Trees used in agroforestry practices, such as windbreaks, provide a variety of ecosystem benefits and are recognized globally as an important land use. However, efforts to inventory and monitor agroforestry land use have been sporadic, short-lived, or focused on small spatial extents. There are a variety of satellite-derived datasets that provide information about tree cover over broad spatial ...

AIM This study provides regional estimates of forest cover in dry African ecoregions and the changes in forest cover that occurred there between 1990 and 2000, using a systematic sample of medium-resolution satellite imagery which was processed consistently across the continent. LOCATION The study area corresponds to the dry forests and woodlands of Africa between the humid forests and the se...