Rate Of Tropical Deforestation Research Articles

TROPICAL DEFORESTATION AND GREENHOUSE‐GAS EMISSIONS

A recent (2002) analysis concluded that rates of tropical deforestation and atmospheric carbon emissions during the 1990–1997 interval were lower than previously suggested. We challenged this assertion with respect to tropical carbon emissions, but our conclusions were disputed by the authors of the original study. Here we provide further evidence to support our conclusion that the effect of tropical deforestation on greenhouse‐gas emissions and global warming is substantial. At least for Brazilian Amazonia, the net impact of tropical deforestation on global warming may be more than double that estimated in the recent study.

Population limitation in migrants

Unlike resident bird species, the population sizes of migratory species can be influenced by conditions in more than one part of the world. Changes in the numbers of migrant birds, either long‐term or year‐to‐year, may be caused by changes in conditions in the breeding or wintering areas or both. The strongest driver of numerical change is provided in whichever area the per capita effects of adverse factors on survival or fecundity are greatest. Examples are given of some species whose numbers have changed in association with conditions in breeding areas, and of others whose numbers have changed in association with conditions in wintering areas. In a few such species, the effects of potential limiting factors have been confirmed locally by experiment. In theory, population sizes might also be limited by severe competition at restricted stopover sites, where bird densities are often high and food supplies heavily depleted, but (with one striking exception) the evidence is as yet no more than suggestive. In some species, habitats occupied in wintering and migration areas, and their associated food supplies, can influence the body condition, migration dates and subsequent breeding success of migrants. Body reserves accumulated in spring by large waterfowl serve for migration and for subsequent breeding, and females with the largest reserves are most likely to produce young. Hence, the conditions experienced by individuals in winter in one region can affect their subsequent breeding success in another region. Such effects are apparent at the level of the individual and at the level of the population. Similarly, the numbers of young produced in one region could, through density‐dependent processes, affect subsequent overall mortality in another region. Events in breeding, migration and wintering areas are thus interlinked in their effects on bird numbers. Although in the last 30–40 years the numbers of some tropical wintering birds have declined in western Europe and others in eastern North America, the causes seem to differ. In Europe, declines have mainly involved species that winter in the arid savannas of tropical Africa, which have suffered from the effects of drought and increasing desertification. In several species, annual fluctuations in numbers and adult survival rates were correlated with annual fluctuations in rainfall, and by implication in winter food supplies. In North America, by contrast, numerical declines have affected many species that breed and winter in forest, especially those eastern species favouring the forest interior. Declines have been attributed ultimately to human‐induced changes in the breeding range, particularly forest fragmentation, which have led to increases in the densities of nest predators and parasitic cowbirds. These in turn are thought to have caused declines in the breeding success of some neotropical migrants, which is now too low to offset the usual adult mortality, but as yet convincing evidence is available for only a minority of species. The breeding rates and population changes of some migratory species have been influenced by natural changes in the availability of defoliating caterpillars. In other species, tropical deforestation is likely to have played the major role in population decline, and if recent rates of tropical deforestation continue, it is likely to affect an increasing range of migratory species in the future. Not all such species are likely to be affected adversely by deforestation, however, and some may benefit from the resulting habitat changes.

Facilitating natural regeneration in Saccharum spontaneum (L.) grasslands within the Panama Canal Watershed: effects of tree species and tree structure on vegetation recruitment patterns

To counteract the escalating rates of tropical deforestation, it is essential that we not only minimize forest loss, but that we create effective reforestation strategies. This study investigates understory recruitment patterns in mixed native species plantations along the Panama Canal that were established in grasslands dominated by the invasive exotic species Saccharum spontaneum (L.) Graminae. We test the hypothesis that regeneration rates vary significantly by overstory tree species and overstory tree structure, and explore the mechanisms generating such patterns. Of the seven tree species sampled, Inga spp. recruits significantly more tree seedlings than any other species. Additionally, crown foliage density appears to be the most significant structural factor determining rates of understory tree species regeneration. A survey of bird activity in the plantations and in unplanted areas indicates that birds generally visit large trees and that those tree species most frequently visited by birds also have the greatest density of understory tree seedlings. These results support the hypothesis that tree structure significantly affects regeneration patterns, and suggests that bird dispersal may be a fundamental driver in seedling recruitment. Furthermore, results indicate that the presence of any tree species in a reforestation plot increases the understory species richness and species cover relative to non-reforested areas, while significantly reducing the degree of S. spontaneum dominance. While active reforestation appears to facilitate forest regeneration in areas occupied in S. spontaneum, tree species and tree structure are important factors to consider when designing reforestation programs that are intended to facilitate natural regeneration.

Protecting terrestrial ecosystems and the climate through a global carbon market.

Protecting terrestrial ecosystems through international environmental laws requires the development of economic mechanisms that value the Earth's natural systems. The major international treaties to address ecosystem protection lack meaningful binding obligations and the requisite financial instruments to affect large-scale conservation. The Kyoto Protocol's emissions-trading framework creates economic incentives for nations to reduce greenhouse-gas (GHG) emissions cost effectively. Incorporating GHG impacts from land-use activities into this system would create a market for an important ecosystem service provided by forests and agricultural lands: sequestration of atmospheric carbon. This would spur conservation efforts while reducing the 20% of anthropogenic CO(2) emissions produced by land-use change, particularly tropical deforestation. The Kyoto negotiations surrounding land-use activities have been hampered by a lack of robust carbon inventory data. Moreover, the Protocol's provisions agreed to in Kyoto made it difficult to incorporate carbon-sequestering land-use activities into the emissions-trading framework without undermining the atmospheric GHG reductions contemplated in the treaty. Subsequent negotiations since 1997 failed to produce a crediting system that provides meaningful incentives for enhanced carbon sequestration. Notably, credit for reducing rates of tropical deforestation was explicitly excluded from the Protocol. Ultimately, an effective GHG emissions-trading framework will require full carbon accounting for all emissions and sequestration from terrestrial ecosystems. Improved inventory systems and capacity building for developing nations will, therefore, be necessary.

Tropical deforestation in the Bolivian Amazon

The distributions of forest and deforestation throughout the tropics are poorly known despite their importance to regional biodiversity and global climate and biodiversity. Deforestation estimates based on surveys or sampling have large errors, and high-resolution, wall-to-wall mapping of tropical forests is necessary to assess the impacts of fragmentation. Landsat satellite images from the mid-1980s and early 1990s were thus used to map closed-canopy tropical forest extent and anthropogenic deforestation in an approximately 700 000 km2 area of Amazonian Bolivia with precipitation >1000 mm yr−1. Total potential forest cover extent, including tropical deciduous forest, was 448 700 km2, while the area of natural non-forest formations was 245 100 km2. The area deforested was 15 500 km2 in the mid-1980s and 24 700 km2 by the early 1990s. The rate of tropical deforestation in the forest zone of Bolivia with >1000 mm yr−1 precipitation below 1500 m elevation and north of 19° S, was 1529 km2 yr−1 from 1985–1986 to 1992–1994. Our estimates of deforestation are significantly lower than those reported by the Food and Agriculture Organization of the United Nations (FAO). We document a spatially-concentrated ‘deforestation zone’ in Santa Cruz where >60% of the Bolivian deforestation has occurred. These results indicate that the rate of deforestation in Bolivia has been rapid despite a relatively small human population, and, as in Brazil, clearance has concentrated in the more deciduous forests.

Sampling for forest cover change assessment at the pan-tropical scale

A major component of the Joint Research Centre's TREES-II project is the assessment of deforestation rates in moist tropical regions for the period 1992 to 1997 using a statistical sample of fine spatial resolution satellite image pairs. It is widely recognized that spatial stratification can reduce the variance of estimates in spatial sampling designs. However, at the pan-tropical scale little reliable spatial information is available to stratify on the basis of deforestation rates. This paper describes a novel sampling scheme for assessing tropical deforestation rates. Stratification is performed using percentages of forest area (derived from National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data) and areas of known deforestation activity (elucidated from expert consultation) estimated for each sampling unit. Sample site selection is performed by using a sample frame based on a tessellation of hexagons on a sphere. This approach allows for a sensor-independent sample from which unbiased estimators and error variance may be computed. The scheme is currently in the implementation phase for the tropical belt, but can be extended to the global scale.

Canopy removal and residual stand damage during controlled selective logging in lowland swamp forest of northeast Costa Rica

Sustainable timber extraction through selective logging has been proposed as a method of forest management that can help curtail the rate of tropical deforestation. This paper reports canopy removal and residual stand damage estimates for a controlled selective logging operation in lowland swamp forest of northeast Costa Rica. The logging procedure only harvested Carapa nicaraguensis (Meliaceae) trees of at least 70 cm dbh (diameter at 1.4 m or above buttresses). Logging removed 6.3 trees ha −1 (SD = 4.2) from 28 ha, and 45.8 m 3 ha −1 from a 7 ha subsample. Canopy cover was 91% (SD = 4.5) in undisturbed forest, and 73% (SD = 12.4) in logged forest. Post-logging canopy cover was negatively correlated with the number of trees extracted ha −1. Prior to logging, 65% of total gap area was contained in gaps less than 250 m 2. After logging, gaps of over 500 m 2 represented 78% of total gap area. Stand basal area in 7 ha of inventoried forest was reduced by 18.3%, and 17.6% of residual stems were damaged or killed. Wet soil conditions required the use of 5.3% of residual stems to construct corduroy skid trails. Thus, 30% of all residual stem damage resulted from soil conservation efforts. Stem damage estimates were compared with those reported from uncontrolled tropical logging operations. Although absolute levels of residual damage during controlled logging were quite low, there was no conclusive evidence that total residual damage was relatively lower than intensity-adjusted estimates of those other operations. In contrast, canopy removal during logging was lower than that in two other neotropical studies. Both residual damage and canopy removal can be decreased further by incorporating stricter felling guidelines; measures to reduce necessary levels of skid trail fortification would also decrease residual damage. The results are discussed in the broad context of tropical forest management. A conservative approach to tropical forestry increases the possibility of sustainable extraction of the resource.

Democracy, political instability and tropical deforestation

The alarming rate of depletion of tropical forests and the economic, social, and environmental implications are serious issues facing the world. Very prominent among the myriad factors at play is the political environment within these tropical countries. This study therefore investigates to what extent the rate of tropical deforestation is exacerbated by the democratic/non-democratic nature of the governments in power. We construct a democracy index variable for fifty-five countries across the four regions of the tropical world. The average annual deforestation from 1981–1985, is compared to the democracy index variable. We find a strong negative correlation between the level of democracy and the rate of tropical forest exploitation. The global policy implications of this finding are outlined.

Forest losses predict bird extinctions in eastern North America.

Claims that there will be a massive loss of species as tropical forests are cleared are based on the relationship between habitat area and the number of species. Few studies calibrate extinction with habitat reduction. Critics raise doubts about this calibration, noting that there has been extensive clearing of the eastern North American forest, yet only 4 of its approximately 200 bird species have gone extinct. We analyze the distribution of bird species and the timing and extent of forest loss. The forest losses were not concurrent across the region. Based on the maximum extent of forest losses, our calculations predict fewer extinctions than the number observed. At most, there are 28 species of birds restricted to the region. Only these species would be at risk even if all the forests were cleared. Far from providing comfort to those who argue that the current rapid rate of tropical deforestation might cause fewer extinctions than often claimed, our results suggest that the losses may be worse. In contrast to eastern North America, small regions of tropical forest often hold hundreds of endemic bird species.

When Do Property Rights Matter? Open Access, Informal Social Controls, and Deforestation in the Ecuadorian Amazon

In recent years a number of analysts have argued that open access explains why people have destroyed so many tropical forests so rapidly. Under conditions of open access loggers and colonists clear forested land rapidly out of a fear that others will extract valuable resources from these places before they will. This paper questions the magnitude of the ‘open access’ effect. Ethnographic data from the Ecuadorian Amazon suggest that, in the absence of formally constituted property rights, informal social controls limit access to the forests and indirectly limit rates of tropical deforestation. Comparisons with land clearing in the Brazilian Amazon suggest that informal controls only retard deforestation in relatively stable frontier settings. The paper concludes with a discussion of the policy implications of these findings.

Third-world debt and tropical deforestation

The deforestation and degradation of tropical forests are taking place at an extremely rapid pace. According to the Food and Agriculture Organization (FAO), the estimated annual rate of tropical deforestation during the 1981–1985 period was 113 846 square kilometers or 0.6% of the 1981 total forested area. The implications of the loss of these forests are staggering (Myers, N., 1989. Deforestation Rates in Tropical Forests and Their Climatic Implications. Friends of the Earth, London). Tropical forests are extremely rich ecosystems which support a disproportionately large share of the world's plant and animal species. Forests play a crucial role in both nutrient and hydrological cycling and may provide sustainable economic benefits through managed harvesting of timber and the collection of non-timber products such as fruits, nuts, and rubber. Also, deforestation is a significant source of global warming through its effects on the global carbon cycle. This paper focuses on the relationship between debt and deforestation, examining conceptual and empirical arguments that debt is a source of deforestation pressure. Our study develops a behavioral model which suggests that debt can lead to myopic behavior, leading to deforestation rates that may not be optimal in the long run, but are necessary in the short run to meet current constraints. Then, country-by-country data on debt, deforestation, and other variables are analyzed with regression analysis. It is shown that debt is significantly correlated with deforestation under a wide variety of assumptions and specifications. Our results indicate that debt is an important factor in the deforestation of tropical countries. There are certainly other sources of deforestation, both micro- and macroeconomic, which may vary significantly from country to country. However, we focus on debt because of its dominant role in the economies of developing countries, and because of the increased use of debt-for-nature swaps. The link between debt and deforestation that is suggested in this paper implies that debt-for-nature swaps may have a dual effect on deforestation. First, the contractual agreement is designed to preserve forests as part of the swap. Second, the reduction in debt may itself reduce the pressure to deforest, although this indirect effect is small. Our research provides evidence that reducing debt reduces deforestation, which may be an argument to offer deforesting third-world countries some form of debt relief, and to utilize more fully debt-for-nature swaps as a tool for preserving environmental quality.

Tropical deforestation and atmospheric carbon dioxide

Recent estimates of the net release of carbon to the atmosphere from deforestation in the tropics have ranged between 0.4 and 2.5 × 1015 g yr−1. Two things have happened to require a revision of these estimates. First, refinements of the methods used to estimate the stocks of carbon in the vegetation of tropical forests have produced new estimates that are intermediate between the previous high and low estimates of carbon stocks. When these revised estimates were used here to calculate the emissions of carbon from deforestation, the new range was 1.0–2.0 × 1015 g C. Second, the previous range of estimates of flux was based on rates of deforestation in 1980. Myers' recent estimate of the rates of tropical deforestation in 1989 is about 90% higher than the rates just 10 years ago. When these recent rates were used to calculate the current net flux of carbon to the atmosphere, the range was between 1.6 and 2.7 × 1015 g C. Other uncertainties expanded this range, however, to 1.1–3.6 × 1015 g C yr−1. Three factors contributed about equally to the expanded range: rates of deforestation, the fate of deforested lands (permanent or temporary clearing), and carbon stocks of forests, including anthropogenic reductions of carbon stocks within forests (thinning or degradation).

An analysis of anthropogenic deforestation using logistic regression and GIS

The anthropogenic deforestation occurring throughout the tropical world is one of the great crises of our time. To better understand the dimensions of this problem, a number of studies have sought to quantify the extent and rate of tropical forest loss. However, environmental planners and managers need to know more than the extent and rate of tropical deforestation. There is a need for predictability, i.e. which areas are most susceptible to deforestation. This study demonstrates a methodology for predicting those areas with the greatest propensity for deforestation based on natural and cultural landscape variables. Logistic regression analysis was used to determine variables most closely associated with deforestation. The independent variables most strongly associated with the forested/deforested dependent variable were location of forested areas in relation to the forested/deforested edge in an earlier time period, to the location of access in an earlier time period, and to the location of habitation in an earlier time period. GIS analysis was then used to verify spatially the close statistical relationship between the dependent variable and each of the independent variables selected by the logistic regression modeling.

PLANTATION FORESTRY IN THE TROPICS – TRENDS AND PROSPECTS

SUMMARY Greater changes have taken place in plantation forestry since the late 1970s than at any other time. The area of new planting is probably more than 1 million ha per annum: more than double the figure of 15 years ago but still only one tenth of the current rate of tropical deforestation. The bulk of new projects and initiatives now aim to meet social and environmental forestry objectives rather than industrial ones. Integration of forestry and farming (agroforestry) is now being widely evaluated. Arid zone planting, especially to meet fodder, firewood and fencing requirements, has greatly increased. Funding for plantation development has encouraged social forestry programmes as these are now accorded high priority by development banks and bilateral aid projects etc, and has been aided in the social forestry sector by greatly increased involvement of non-governmental organizations (NGOs). The rate of new planting must continue to increase and the priority of meeting social objectives maintained if i...