Regional Deforestation Research Articles

Tropical forests: regional paths of destruction and regeneration in the late twentieth century

List of FiguresList of TablesPrefaceAcknowledgments1. Introduction2. Theory and Method in Studying Regional Deforestation Processes3. Central America and the Caribbean: Island and Isthmus Deforestation4. The Amazon Basin: The Breakdown of Passive Protection5. West Africa: From Cocoa Groves in Forests to Food Crops in Scrub Growth6. Central Africa: Passive Protections for Rain Forests7. East Africa: Sustainable Spots Surrounded by Degrading Expanses8. South Asia: A Turning Point for Forests?9. Southeast Asia: Deforesting the Lowlands, Afforesting the Highlands10. Through a Regional Lens: Conservation Policies in Large and Small ForestsAppendix: Case Studies and Accompanying QCAs for Each RegionNotesReferencesIndex

Driving forces of tropical deforestation: The role of remote sensing and spatial models

Remote sensing technologies are increasingly used to monitor landscape change in many parts of the world. While the availability of extensive and timely imagery from various satellite sensors can aid in identifying the rates and patterns of deforestation, modelling techniques can evaluate the socioeconomic and biophysical forces driving deforestation processes. This paper briefly reviews some emerging spatial methodologies aimed at identifying driving forces of land use change and applies one such methodology to understand deforestation in Mexico. Satellite image classification, change analysis and econometric modelling are used to identify the rates, hotspots and drivers of deforestation in a case study of the southern Yucatán peninsular region, an enumerated global hotspot of biodiversity and tropical deforestation. In particular, the relative roles of biophysical and socioeconomic factors in driving regional deforestation rates are evaluated. Such methodological approaches can be applied to other regions of the forested tropics and contribute insights to conservation planning and policy.

O desmatamento na Amazônia e a importância das áreas protegidas

O MODELO da ocupação demográfica da Amazônia legalnos últimos cinqueta anos tem levado a níveis significativos de desmatamento, resultante de múltiplos fatores, tais como a abertura de estradas pioneiras, o crescimento das cidades, a ampliação de pecuária extensiva, a acelerada exploração madeireira e a crescente agricultura intensiva de monoculturas. A área cumulativa desmatada na Amazônia legal brasileira chegou a cerca de 653.000 km² em 2003, correspondendo a 16,3% da região. Este estudo visou a determinar o desmatamento dentro e fora dos atuais Unidades de Conservação (UC) e Terras Indígenas (TI) na Amazônia legal, nos estados de Mato Grosso, Rondônia e Pará, que, juntos, corresponderam por mais de 90% do desmatamento observado entre 2001 e 2003. Os resultados mostraram que o desmatamento foi cerca de dez a vinte vezes menor dentro das Unidades de Conservação e Terras Indígenas do que em áreas contíguas fora delas. Isto demonstra a importância dessas áreas protegidas para diminuir o processo do desmatamento nos três estados. Isto refuta a hipótese generalizada de que estas áreas não cumprissem a sua função principal na conservação e uso racional dos recursos na Amazônia legal.

Paleoproductivity of eastern Lake Ontario over the past 10,000 years

We evaluated relative levels of paleo‐primary productivity in eastern Lake Ontario during the past ~10,000 yr via analysis of inorganic and organic sediment from the Rochester Basin. There was significant natural variability in primary production correlative with Holocene climate change. The cold post‐Younger Dryas interval (~10–9.4 ka) was a time of minimal levels of primary production. The warm Holocene Hypsithermal interval (~9.4–5.3 ka) had much higher levels of primary production but was more variable, including five well‐defined cycles that have an average period of ~750 yr. The largest negative anomaly in primary productivity occurred during the 8.2‐ka climate event (~8.4–8.0 ka), a time of cold, dry conditions. Another negative anomaly occurred in association with the Nipissing flood (~6.3–5.3 ka), which triggered a regional cooling event. The cool Holocene Neoglacial interval (~5.3 ka to ~1850 A.D.) was characterized by lower, but more stable, levels of primary production, as well as by a cessation of calcite precipitation and the onset of diatom productivity. During the historic interval (~1850–1940 A.D.), there was a dramatic increase in primary production to unprecedented levels over the past 10,000 yr, as well as a 30–fold increase in sediment accumulation rates. These large, abrupt changes occurred in response to regional deforestation, anthropogenic nutrient loading, and increased chemical weathering due to acid rain. We project that, during 21st century global warming, eastern Lake Ontario will evolve into an ecosystem similar to that during the Holocene Hypsithermal.

Flood deposits penecontemporaneous with ∼0.8 Ma tektite fall in NE Thailand: impact-induced environmental effects?

Although a crater is not yet identified, the Australasian tektite strewn field provides evidence that a major impact cratering event took place in the Southeast Asian region at ∼0.8 Ma, just prior to the Brunhes/Matuyama geomagnetic polarity reversal. Paleomagnetic evidence including reversed polarity in mud lens closely associated with in situ tektites suggests that tektite-bearing flood deposits near Ban Ta Chang and Chum Phuang in northeast Thailand are penecontemporaneous with the impact event. The deposits include abundant organic debris, including whole tree trunks and mammal bones, that preserved due to reducing conditions, which are also responsible for the presence of abundant iron sulphides. Sedimentological observations suggest a series of major flood events that are out of character with the modern meandering river system to which they are related. The deposits are consistent with the effects of regional deforestation, increased run off and erosion, and other environmental disruptions expected in the aftermath of a major impact event.

Effects of an experimental drought on soil emissions of carbon dioxide, methane, nitrous oxide, and nitric oxide in a moist tropical forest

AbstractChanges in precipitation in the Amazon Basin resulting from regional deforestation, global warming, and El Niño events may affect emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and nitric oxide (NO) from soils. Changes in soil emissions of radiatively important gases could have feedback implications for regional and global climates. Here we report results of a large‐scale (1 ha) throughfall exclusion experiment conducted in a mature evergreen forest near Santarém, Brazil. The exclusion manipulation lowered annual N2O emissions by >40% and increased rates of consumption of atmospheric CH4 by a factor of >4. No treatment effect has yet been detected for NO and CO2 fluxes. The responses of these microbial processes after three rainy seasons of the exclusion treatment are characteristic of a direct effect of soil aeration on denitrification, methanogenesis, and methanotrophy. An anticipated second phase response, in which drought‐induced plant mortality is followed by increased mineralization of C and N substrates from dead fine roots and by increased foraging of termites on dead coarse roots, has not yet been detected. Analyses of depth profiles of N2O and CO2 concentrations with a diffusivity model revealed that the top 25 cm soil is the site of most of the wet season production of N2O, whereas significant CO2 production occurs down to 100 cm in both seasons, and small production of CO2 occurs to at least 1100 cm depth. The diffusivity‐based estimates of CO2 production as a function of depth were strongly correlated with fine root biomass, indicating that trends in belowground C allocation may be inferred from monitoring and modeling profiles of H2O and CO2.

Natural controls and human impacts on stream nutrient concentrations in a deforested region of the Brazilian Amazon basin

This study documents regional patterns in stream nitrogen and phosphorus concentrations in the Brazilian state of Rondonia in the southwestern Amazon basin, and interprets the patterns as functions of watershed soil properties, deforestation extent, and urban population density. The survey includes 77 different locations sampled in the dry and wet seasons, with a watershed size range from 1.8 to 33,000 km2 over a total area of approximately 140,000 km2. A sequential regression technique is used to separate the effects of natural watersheds properties and anthropogenic disturbance on nutrients and chloride. Natural variation in soil texture explains most of the variance in stream nitrate concentrations, while deforestation extent and urban population density explain most of the variance in stream chloride (Cl) and total dissolved nitrogen (TDN) concentrations. Stream TDN, total dissolved phosphorus (TDP), particulate phosphorus (PP) and Cl concentrations all increase non-linearly with deforestation extent in the dry season after controlling for natural variability due to soil type. Stream nutrient and Cl disturbances are observed only in watersheds more than 66–75% deforested (watershed area range 2–300 km2), suggesting stream nutrient concentrations are resistant to perturbation from vegetation conversion below a 66–75% threshold. In heavily deforested watersheds, stream Cl shows the largest changes in concentration (12 ± 6 times forested background), followed by TDP (2.3 ± 1.5), PP (1.9 ± 0.8) and TDN (1.7 ± 0.5). Wet season signals in Cl and TDP are diluted relative to the dry season, and no land use signal is observed in wet season TDN, PN, or PP. Stream TDN and TDP concentrations in non-urban watersheds both correlate with stream Cl, suggesting that sources other than vegetation and soil organic matter contribute to enhanced nutrient concentrations. Small, urbanized watersheds (5–20 km2) have up to 40 times the chloride and 10 times the TDN concentrations of forested catchments in the dry season. Several large watersheds (∼1000–3000 km2) with urban populations show higher Cl, TDN and TDP levels than any small pasture watershed, suggesting that human impacts on nutrient concentrations in large river systems may be dominated by urban areas. Anthropogenic disturbance of dry-season stream Cl and TDN is detectable in large streams draining deforested and urbanized watersheds up to 33,000 km2. We conclude that regional deforestation and urbanization result in changes in stream Cl, N and P concentrations at wide range of scales, from small pasture streams to large river systems.

The effect of tropical deforestation on stingless bees of the genus Melipona (Insecta: Hymenoptera: Apidae: Meliponini) in central Rondonia, Brazil

Aim(1) To determine whether deforestation has affected the incidence of species of Melipona in an area undergoing deforestation. (2) To highlight the potential use of GIS and remote‐sensed environmental variables in studies of insects as bioindicators of landscape change.LocationCentral Rondonia, Brazil in the south‐western Amazon Basin, an area under intense deforestation pressure for agriculture and cattle ranching since the 1970s.MethodsStingless bees of the genus Melipona were sampled outside of forest cover on iron‐weed, Vernonia polynthes Less., at 69 locations along a deforestation gradient within a 3150‐km2 study area. We related species richness and composition for each sample point to local and regional deforestation variables, including geographical position along the deforestation gradient, distance to the forest, and percentage of primary forest coverage within a 1 and 2 km radius of the sample points. Deforestation variables were generated using GIS and LANDSAT TM imagery of the study area. Redundancy analysis was used to illustrate the relationship between species incidence, the deforestation variables, and other possible confounding environmental variables.ResultsSeven species were found within the study area. Two species (M. seminigra abunensis Cockerell, 1912 and M. grandis Guérin, 1844) appear not to be affected by deforestation yet, occurring evenly across the deforestation gradient. Two other common species (M. melanoventer Schwarz, 1932 and M. rufiventris brachychaeta Moure, 1950), however, occurred mainly towards the end of the gradient where the forest was more intact, indicating relative susceptibility to deforestation. Melipona species richness, ranging from 1 to 5 species, was inversely related to distance to forest and directly related to percentage of forest cover.Main conclusionsAdverse effects of deforestation on Melipona are detectable in the study area, despite the fact that significant areas of tropical forest cover remain. The species that are most affected may be considered indicators of landscape change, and efforts to protect these species could involve their use in beekeeping programmes designed to raise rural incomes and maintain regional biodiversity.

Traditional resource-use systems and tropical deforestation in a multi-ethnic region in North-West Ecuador

There is general consensus that resource-use strategies of recent migrants in tropical rainforests result in extensive deforestation and other negative environmental impacts. Less agreement exists about the nature and extent of the impact of indigenous and long-standing migrant communities living in rainforests. It has often been argued that the high value these communities place on local resources results in environmental conservation in areas under their control, but this is being increasingly challenged. The aim of this study was to contribute to this debate by comparing the regional environmental impact of indigenous and non-indigenous households in North-west Ecuador, with emphasis on tropical deforestation. The basic premise was that long-term resource-use strategies and related decision-making processes should be discernible as characteristic land-use patterns. Three indigenous and non-indigenous populations coexist in the study region, and demographic, land-use and historical sources of information were used to evaluate their relationship to regional deforestation in the period 1983-93. No significant differences were found in the recent deforestation associated with each group based on their cultural or ethnic background, although differences did exist in the past. The need to differentiate between a given environmental impact and the decision-making process behind it was also evident. In North-west Ecuador, markets, factors of production, and access to and control of resources, are key for understanding the environmental impact of local communities. Low-impact resource-uses often result from low-return productive activities in forest environments with low labour opportunity costs, high discount rates for income generated through activities compromising food security, and from uncertainty about future conditions. Environmental policy-making and programme design need to recognize this relationship. Conservation will be possible only if the perceived benefit to local users is greater than that of resource transformation, both of which respond to the dominant environmental, economic and social conditions at a given time and place. Creating or fostering the appropriate conditions should be a key objective of both.

Speleothems as high-resolution paleoenvironment archives: Records from northeastern China

The isotopic compositions of oxygen and carbon and trace concentrations of magnesium and strontium in speleothems formed in limestone caves respond to climate changes outside the caves. Measurements of these properties on a stalagmite from Shihua Cave near Beijing, China, allowed reconstruction of the regional changes in precipitation, temperature and nature of vegetation. Over the last ∼ 500 years, there were fourteen precipitation cycles with a periodicity of 30–40 years, which may well reflect fluctuations in the strength of the East Asian summer monsoons reaching northeastern China. Relative to the mean temperature of this time interval, the period 1620–1900 AD was cold and periods 1520–1620 and 1900–1994 were warm. Over the last ∼ 3000-years, about eight wet/cool-dry/warm climatic cycles of 300–400 years duration occurred, the latest wet/cool half cycle corresponding to the Little Ice Age. The δ13C record registers the anthropogenic activities of fossil fuel CO2 combustion in recent decades and regional deforestation between 13 and 16 centuries when Beijing was bustling with palatial constructions and being developed into the world’s most populated city.

Paper Forests: Imagining and deploying exogenous ecologies in arid India

Debate about the causes and consequences of regional deforestation in India has paved the way for calls to action and intervention, and state-sponsored afforestation has led to government claims of progress against land degradation. Census statistics from the arid state of Rajasthan show a tide of forests reclaiming the land. These trends obscure crucial realities that continue to undermine the claims of the state: forest ecosystems continue to disappear, expanding cover is characterized by an ecologically narrow range of species, and forest management remains rooted in a decision structure that fails to educe local knowledge and experience. More fundamentally, the flaws in the Rajasthani forest campaign reflect an entrenched pattern that has long guided authorities in the region; to govern the landscape, the state must quite literally construct forests—as mental categories, discursive tropes, and material realities—where none have existed before. The material conditions of tree cover are, in this way, influenced by the discursive forms of forest imported into the region. This paper surveys the contradictory trends in Rajasthani land cover, interrogating the relationship between the forests that expand on paper and those that dwindle on the ground. In the process, the paper contributes to ongoing work in post-structural political ecology by asking how discourse matters in the reconstitution of material ecologies and by linking the construction of ecological categories to the formation of landscapes.

Isotopic record of lead pollution in lake sediments from the northeastern United States

Although it is common knowledge that Pb concentrations have increased in lake sediments in the northeastern United States over the last 150 years, the processes responsible have been the subject of debate. In this study, differences in lead isotopic compositions and concentrations in sediment from large lakes (Lake Erie, Ontario, and Michigan) and small ones (Deep Lake and Lake Andrus) are used to infer temporal changes in the source(s) of anthropogenic Pb in the Great Lakes region. A natural (background) component of Pb is present in sediment deposited prior to 1860 in Lake Erie and the other lakes as indicated from low Pb concentrations and uniform lead isotopic compositions. Changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic Pb superimposed on the natural component such as regional deforestation from 1860–1890 followed by coal combustion and ore smelting through 1930. Combustion of leaded gasoline was the dominant anthropogenic Pb source to the atmosphere (and by inference to lake sediment) from 1930–1980. Temporal changes in lead isotopic compositions in lake sediment suggest that the source of the Pb used in gasoline additives gradually changed from 1930 to present. The best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased Pb production from the Viburnum Trend deposits in Missouri (present in all lakes except Ontario). However, the changes in lead isotopic compositions are much less variable than and do not parallel those calculated on the basis of annual United States mine production and imports. Rather, anthropogenic recycling of Pb as well as natural mixing processes during emission, transport, and deposition of Pb in lake sediment control most of the variation in lead isotope ratios. Differences in lead isotopic ratios in Lake Michigan, Erie, and Deep Lake sediment preserve regional differences in lead isotopic ratios from U.S. and Canadian sources first noted in aerosols by Sturges and Barrie (1987). More localized sources of Pb (such as point discharges) are needed to explain the results from Lake Ontario and Andrus.

Extraction of a high-value natural resource in Amazonia: the case of mahogany

Mahogany, Swietenia macrophylla King, is by far the most valuable timber species in the Brazilian Amazon: 1 m 3 of export-quality sawn wood was valued at about $700 in the early 1990s. We studied the structure and economy of the mahogany companies operating in southern Pará State, the major mahogany processing center in the Brazilian Amazon. Of the 86 mills in operation in this region, 24 specialized in mahogany and were responsible for processing 90% of the mahogany harvest. Many of these mahogany mills (60%) were established in the 1980s. By the early 1990s, most (91%) were vertically integrated—participating in forest logging, log transport, mill processing, and marketing. Mahogany companies achieved good profits in the early 1990s. A typical mill with one band saw produced, on average, 4500 m 3 of sawn wood year −1 from 9900 m 3 of roundwood. The value of this sawn wood was approximately $3 000 000; annual profits for such a company were approximately $800 000. In three logging operations that we studied, an average of 5 m 3 of mahogany logs were extracted per hectare; this is equivalent to the extraction of about one mahogany tree per hectare. However, future cuts of mahogany are in doubt: in surveys of recently logged sites we encountered, on average, only 0.25 mahogany trees of at least 30 cm diameter at breast height (dbh) per hectare and no trees between 10 and 30 cm dbh. Mahogany seedings were also rare. Logging damage can be great on a local scale. Thirty-one trees at least 10 cm dbh were severely damaged for each mahogany tree harvested; approximately 1100 m 2 of forest ground surface were scraped clean or trampled for each mahogany tree removed. However, because mahogany trees are usually distributed in widely scattered patches only a small fraction of the region's forest has been directly disturbed by this logging. Nonetheless, the specific effect on Swietenia macrophylla—its population numbers and genetic structure—may be significant. Moreover, mahogany logging indirectly contributes to regional deforestation. Logging companies have opened up some 3000 km of logging roads in southern Pará and mahogany logging has been documented in each of the region's 15 Indian Reserves. After logging, there is a growing trend to convert forests to cattle pasture, in part perhaps, because the prospects for future mahogany harvests do not appear to be good. We conclude our paper with a discussion of initiatives in the policy, business, and technical sectors aimed at promoting the sustainable management of mahogany forests in the Brazilian Amazon.

Smokestacks in the rainforest: Industrial development and deforestation in the Amazon basin

In the eastern Brazilian Amazon abundant natural resources, strategic infrastructure, and generous government incentives are spurring a rush to establish charcoal-consuming industries. Annual fuelwood demand for these industries is projected to exceed 14 million tons; fuelwood is supplied primarily by native tropical forests. Because the prospects for sustained management are unlikely, I calculate that over 1,500 km 2 of forest land could be destroyed for fuelwood production each year, thus exacerbating regional deforestation and undermining the resources base on which industries depend. This study shows that in humid tropical regions, large-scale industrialization can be a powerful catalyst for environmental degradation.

Support for global Science: Remote sensing's challenge

Remote sensing uses a wide variety of techniques and methods. Resulting data are analyzed by man and machine, using both analog and digital technology. The newest and most important initiatives in the U. S. civilian space program currently revolve around the space station complex, which includes the core station as well as co-orbiting and polar satellite platforms. This proposed suite of platforms and support systems offers a unique potential for facilitating long term, multidisciplinary scientific investigations on a truly global scale. Unlike previous generations of satellites, designed for relatively limited constituencies, the space station offers the potential to provide an integrated source of information which recognizes the scientific interest in investigating the dynamic coupling between the oceans, land surface, and atmosphere. Earth scientist already face problems that are truly global in extent. Problems such as the global carbon balance, regional deforestation, and desertification require new approaches, which combine multidisciplinary, multinational research teams, employing advanced technologies to produce a type, quantity, and quality of data not previously available. The challenge before the international scientific community is to continue to develop both the infrastructure and expertise to, on the one hand, develop the science and technology of remote sensing, while on the other hand, develop an integrated understanding of global life support systems, and work toward a quantiative science of the biosphere.