Forest cover change

forest change

The native forest of Rio Maule-Cobquecura has undergone high degrees of forest clearance during the three decades analysed here, compared to many other forested landscapes. Initially, the forest was severely deforested and degraded due to logging for fuelwood and clearance for cultivation (San Martı´n and Donoso, 1997). Forest losses recorded for other temperate forests, assuming that they were calculated using the compound-interest-rate formula, have generally been lower.

A forest loss rate of 0.53% was estimated for the Klamath-Siskiyou ecoregion, USA, and an overall (cumulative) reduction of forest cover by 10.5% was recorded over the period 1972–1992 (Staus et al., 2002).

In western Oregon, deforestation rates by clearcutting between 1972 and 1995 varied from 0.5% to 1.2% with almost 20% of the total forest impacted (Cohen et al., 2002). Similarly, in other areas of western Oregon, between 1972 and 1988 the rate of deforestation by primarily clearcutting was 1.2% of the entire study area including the wilderness area (Spies et al., 1994). In the central Sikhote-alin Mountains of the Russian Far East, an 18.3% total reduction in conifer forest and a 7.4% total reduction in hardwood forest cover were reported between 1973 and 1992 due mainly to disturbance by timber harvesting (Cushman and Wallin, 2000).

A rate of 0.6%, much lower than that determined for the period 1990–2000 in the present study, was found for the years 1986 to 1996 in the Napo region of western Amazonia (Sierra, 2000). A higher rate of 6% was determined for lowland deciduous forest in eastern Santa Cruz, Bolivia in the middle 1990s (Steininger et al., 2001), thought to be one of the highest deforestation rates reported anywhere in the world. Higher forest loss rate has been reported in an aerial photography-based study conducted for Nothofagus alessandrii forests, a threatened endemic tree to Chile, within the present study area (Bustamante and Castor, 1998). Using also the compound-interest-rate, this forest type declined at a rate of 8.15% between 1981 and 1991. If this rate remains constant, a total extinction of N. alessandrii forest is predicted by the authors in the next decade.

Lower rates of forest loss have been reported in other aerial photography-based studies conducted in the temperate forests of southern hemisphere, using the absolute-loss-rate formulae. For the pre-Andes of the Maule Region of Chile, Olivares (2000) reported deforestation rates in two study areas ranging from 0.5% to 1.4% between 1987 and 1996. For the Coastal Range of Chile, Lara et al. (1989) determined deforestation rates for the period 1978–1987 from 2.0% to 3.5% in the coast of the Maule (including Rio Maule-Cobquecura) and Bio-Bio regions respectively – closely comparable to the period 1990– 2000 analysed for Rio Maule-Cobquecura (3.64%). Conversion to exotic-species plantations and clearance for agricultural land played a major role in these totals (Olivares, 2000; Lara et al., 1989).

For the entire Maule region, a lower annual forest loss of 0.58% was determined between 1994 and 1999, using aerial photographs at difference mapping scales (Conaf and Uach, 2000). Further south, in northern provinces of the Lake region, an overall reduction of 18,100 ha, corresponding to an annual deforestation of 0.3% between 1995 and 1998 was obtained using remote sensing and aerial photographs (Conaf et al., 1999b).

Different types of data and mapping scales have been used at different measurement times in the studies mentioned above, which might have had an effect on the estimation of forest loss. The present study, in contrast, used a consistent type of data over a longer period. An important increase in the area of shrublands was detected by 1990 as a result of the elimination of native forests and arboreus shrublands during 1975–1990. Agricultural and pastureland lands also expanded slightly by 2000 with the reduction of native forests and shrublands in flat areas situated under 200 m elevation.

source: Rapid deforestation and fragmentation of Chilean Temperate Forests
by Cristian Echeverria a,b, * ,1 , David Coomes a , Javier Salas c , Jose´ Marı´a Rey-Benayas d , Antonio Lara b , Adrian Newton