Policy ForumEcology

Conservation Targets in South American Temperate Forests

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Science  13 Nov 1998:
Vol. 282, Issue 5392, pp. 1271-1272
DOI: 10.1126/science.282.5392.1271

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Latin American countries presently rely on the expansion and strengthening of their National Parks and Reserves (NPR) systems as the “safest” investment in conservation (1). Consistent with this view, nature conservation organizations are seeking to double the land area protected in each nation from the current average of 5% (2). This high-priority effort aims to prevent the massive loss of biodiversity that is anticipated as a result of global trends in land use (3, 4). Here we assess whether an initiative of this kind will lead to more effective biodiversity preservation in the confined and endangered temperate forests of southern South America (5, 6).

South American temperate forests occur along a narrow but latitudinally extensive strip of land between 35º and 55ºS, centered in south-central Chile (see the figure). The strong biogeographic isolation of southern temperate forests eliminates the possibility that forests outside the region may act as sources of recolonization after habitat destruction or sudden climate change. Therefore, the NPR system is the only long-term reservoir of temperate forest biodiversity in South America. Our analysis provides new evidence for current discussions about the role of biological reserves in forests. Such discussions are predominantly based on case studies in tropical or Northern Hemisphere forests (7).

Map of the southern cone of South America.

The map shows the distribution of temperate forests (dark red) along the western margin of the continent. The sharp eastern boundary of the temperate forests is determined by the presence of the Andes Range, with maximum elevations from 1000 to 5000 m. Semiarid land barriers (brown) to the north (matorral) and east (steppe) and the location of the nearest wet forests (dark blue patches in upper part of figure) are also shown. (Inset) Map of Chile, showing the six administrative regions (22).

First established in the early 1900s, the Chilean NPR system was one of the pioneers in Latin America (8). In the temperate forest region of south-central Chile, there are 59 parks and reserves protecting 13 million hectares out of a total of 40.5, which represents 29% of the land in this region (9). Among Latin American countries, only Costa Rica, which protects 21% of its territory, comes close to this large proportion of protected area (10). We compared the area of NPR in each administrative region (AR) of Chile within the range of southern temperate forests (see the figure, inset) with the numbers of native vertebrate and tree species, endemic woody genera, and forest types (11). We contrasted these patterns with land covered by plantation forestry and agricultural crops, and with human population density, as indicators of the intensity of land use in south-central Chile (11). Species distributions were obtained from the literature (11), areas classified by land-cover type are from the recently completed survey of Chilean forests (9), and human population data are from the 1992 census (12).

There is a large disparity between the distribution of NPR and regional biodiversity within the latitudinal range of temperate forests. More than 90% of the protected land is concentrated at high latitudes (>43º) outside the richest area of biodiversity. Paradoxically, the amount of land in parks and reserves per AR is inversely correlated with the species richness and endemism for the woody flora and vertebrate fauna, which are considered to be indicator groups (13). Half of the land is under protection in the two most austral ARs, which have the lowest richness of biodiversity indicator groups (see the figure). In contrast, much lower proportions of land (<10% on average) are protected in the biologically richer northern regions. Most dramatically, the areas of highest diversity of forest types and tree species richness, maximum concentration of endemic woody genera, and maximum species richness of native mammals, amphibians, and freshwater fishes (35.6º to 41.3ºS) remain largely outside the extensive NPR system.

Another critical threat to biodiversity in the southern temperate forest region is that areas of high endemism and species richness correspond with areas of high human density and intense land use for plantation forestry, farming, and the raising of livestock (11). Consequently, in the biologically richer ARs, biodiversity is at risk not only because protected areas are lacking but also because of their isolation within an intensely managed mosaic of plantations and urban areas. To quantify the potential impact on protected forest remnants of anthropogenic effects that originate in the matrix, such as the invasion of exotic species, fire, agroindustrial pollution, illegal hunting, and uncontrolled logging, we defined an index of matrix influence (IMI). The IMI was calculated for each AR, based on the proportion of land covered by exotic tree plantations, crops and pastures, and urban areas relative to the remaining cover of native forest (14).

We describe two scenarios: An optimistic one, which assumes that all forest outside reserves will be preserved, and a pessimistic one, in which all forests outside reserves will be cleared and converted to other land uses. Under the pessimistic scenario, the IMI is close to 1 (maximum matrix influence and isolation) in the four northern ARs that are richest in vertebrate species, woody taxa, and endemism, whereas it drops to <0.5 in the two biologically less rich southernmost ARs. The conservation status does improve substantially if all forest remnants in ARs between 35.6º and 41.3ºS were preserved (the optimistic scenario), but the IMI remains high (>0.6) in three biologically rich ARs. Only in region X is there a substantial decrease in matrix influence under the optimistic scenario. We conclude from this analysis that, even in the most optimistic scenario, protected areas of high biodiversity will continue to be threatened because of their isolation and the pervasive influence of the anthropogenic matrix.

An additional concern about the NPR system in south-central Chile (35.6º to 41.3ºS) is that the great majority of NPRs are located above 600 m altitude, so that >90% of the protected forest occurs at high Andean locations, often on large active volcanoes (15). Much of the land in these Andean parks comprises ice and unvegetated terrain (up to 40%) (9). Aside from missing the more productive and biologically richer coast range and lowland forests, this distribution of NPRs leaves most of the protected forest vulnerable to volcanic eruptions. Historical documents and extensive deposits of volcanic ash and debris overlying fossil and glacial soils indicate that southern forests have been repeatedly devastated by volcanic eruptions during the Holocene at intervals varying from every 20 to 100 years (16).

The analysis presented here emphasizes the weakness of conservation targets defined primarily or exclusively as percentages of regional land in national parks and reserves (17). The conservation value of doubling the land in NPRs at the regional or national level will clearly depend on an adequate representation of areas of high diversity and endemism. In South American temperate forests, the first priority should be to rescue forest remnants for conservation in high biodiversity areas and intensely managed areas. As has been shown for the United States (18), in Chile and other Latin American countries this poses a complex social and economic challenge, given that areas requiring urgent protection are generally more accessible, hold more promise for commercial use, are privately owned, and highly priced. The question is whether the governments in Latin America, Chile included, are able to assume the large investments and social costs that will be necessary to change the tenure of high-priority conservation areas in heavily managed landscapes (19). The strong historical trend of allocating reserves in the less desired, remotest, and cheapest land and the traditional conservationist's appeal for extensive wild landscapes should be better balanced by a focus on small, but biologically valuable, forest remnants in heavily managed areas.

Assuming that the protection of much biodiversity in southern temperate forests and other biologically rich regions in Latin America will have to be accomplished in landscapes that continue to be intensely managed and occupied by people, conservation targets cannot be limited to placing new reserves so as to maximize the number of species preserved at a minimum cost (20). Conservation strategies that encourage the careful planning and regulation of land use in the matrix surrounding existing and new protected areas should become a priority. To achieve this goal, a greater investment in environmental education and the development of working partnerships among conservationists, managers, scientists, and private landowners will be essential (21).

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