Patterns and Trends of Forest Loss in the Colombian Guyana

Spatial patterns of tropical deforestation and fragmentation are conditional upon human settlement characteristics. We analyze four different human occupation models (indigenous, colonist frontier, transition and established settlement) in the Colombian Guyana Shield at three different times: 1985, 1992 and 2002, and compared them for: (1) deforestation rates; (2) the amount of forest as classified according to a fragmentation pattern (interior forest, edge forest, perforated forest and forest patch); (3) various fragmentation metrics using repeated measures analysis of variance; and (4) potential future deforestation trends though the implementation of a spatially explicit simulation model. The indigenous and colonist frontier occupation models had low rates of deforestation (0.04%/yr), while the well‐established settlement occupation model had the highest rate (3.68%/yr). Our results indicate that the four occupation models generate three deforestation patterns: diffuse, which can be subdivided into two subpatterns (indigenous and colonist), geometric (transition) and patchy (established settlement). The area with the established settlement model was highly fragmented, while in the transition occupation area, forest loss was gradual and linked to economic activities associated with the expansion of the agricultural frontier. The simulation of future trends revealed that indigenous and colonist areas had a constant, albeit small, loss of forest covers. The other models had a deforestation probability of 0.8 or more. Overall, our results highlight the need for new and urgent policies for reducing forest conversion that consider intraregional variability in human occupation linked to differences in land‐use patterns. Abstract in Spanish is available in the online version of this article.     

Predictive Modelling of Contagious Deforestation in the Brazilian Amazon

Tropical forests are diminishing in extent due primarily to the rapid expansion of agriculture, but the future magnitude and geographical distribution of future tropical deforestation is uncertain. Here, we introduce a dynamic and spatially-explicit model of deforestation that predicts the potential magnitude and spatial pattern of Amazon deforestation. Our model differs from previous models in three ways: (1) it is probabilistic and quantifies uncertainty around predictions and parameters; (2) the overall deforestation rate emerges “bottom up”, as the sum of local-scale deforestation driven by local processes; and (3) deforestation is contagious, such that local deforestation rate increases through time if adjacent locations are deforested. For the scenarios evaluated–pre- and post-PPCDAM (“Plano de Ação para Proteção e Controle do Desmatamento na Amazônia”)–the parameter estimates confirmed that forests near roads and already deforested areas are significantly more likely to be deforested in the near future and less likely in protected areas. Validation tests showed that our model correctly predicted the magnitude and spatial pattern of deforestation that accumulates over time, but that there is very high uncertainty surrounding the exact sequence in which pixels are deforested. The model predicts that under pre-PPCDAM (assuming no change in parameter values due to, for example, changes in government policy), annual deforestation rates would halve between 2050 compared to 2002, although this partly reflects reliance on a static map of the road network. Consistent with other models, under the pre-PPCDAM scenario, states in the south and east of the Brazilian Amazon have a high predicted probability of losing nearly all forest outside of protected areas by 2050. This pattern is less strong in the post-PPCDAM scenario. Contagious spread along roads and through areas lacking formal protection could allow deforestation to reach the core, which is currently experiencing low deforestation rates due to its isolation.     

Land cover change 2002–2005 in Borneo and the role of fire derived from MODIS imagery

Borneo has experienced heavy deforestation and forest degradation during the past two decades. In this study the Moderate Resolution Imaging Spectroradiometer was used to monitor land cover change in Borneo between 2002 and 2005 in order to assess the current extent of the forest cover, the deforestation rate and the role of fire. Using Landsat and ground observation for validation it was possible to discriminate 11 land cover classes. In 2002 57% of the land surface of Borneo was covered with forest of which 74% was dipterocarp and more than 23% peat swamp forest. The average deforestation rate between 2002 and 2005 was 1.7% yr^{− 1}. The carbon-rich ecosystem of peat swamp forests showed a deforestation rate of 2.2%. Almost 98% of all deforestation occurred within a range of 5 km to the forest edge. Fire is highly correlated with land cover changes. Most fires were detected in degraded forests. Ninety-eight per cent of all forest fires were detected in the 5 km buffer zone, underlining that fire is the major driver for forest degradation and deforestation.     

Impact on lake development of changed agricultural watershed exploitation during the last three centuries

The history of the development of Lake Hejrede Sø (Denmark) and the related history of the watershed management were studied based on analyses of macrofossil content, chemical composition and Clostridium perfringens content in sediment cores. Depth-age relations of ecological changes were established through Pb²¹⁰ analyses, and a systematic search for written sources describing the watershed history was carried out.Lake Hejrede Sø used to be a humic, acid but relatively clearwater lake with an extensive submersed vegetation. Owing to deforestation and reclamation of bogs and meadows, the accumulation of nutrients in these ecotones vanished. Subsequently, in early 1800 the lake developed into a clearwater alkaline lake, and later became more eutrophic which resulted in the decline of the submersed vegetation. At the time the annual sediment phosphorus accumulation increased more than twofold, and influx of mineral matter increased drastically. In mid-1900, submersed vegetation had disappeared. The Clostridium perfringens analysis and the historical evidence show that no sewage was discharged to the lake until mid-1900, which implies that changed agricultural watershed exploitation and ecotone reclamation during the 19th century was the cause of the increased nutrient influx, and the deterioration of the lake.Written historical sources confirm the palaeolimnological interpretations and describe the agricultural practices responsible for the development.     

Signature of a Pre-Human Population Decline in the Critically Endangered Reunion Island Endemic Forest Bird Coracina newtoni

The exceptional biodiversity of Reunion Island is threatened by anthropogenic landscape changes that took place during the 350 years of human colonization. During this period the human population size increased dramatically from 250 to 800,000. The arrival of humans together with the development of agriculture, invasive species such as rats and cats, and deforestation has lead to the extinction of more than half of the original vertebrate species of the island. For the remaining species, significant work is being carried out to identify threats and conservation status, but little genetic work has been carried on some of the most endangered species. In the last decade theoretical studies have shown the ability of neutral genetic markers to infer the demographic history of endangered species and identify and date past population size changes (expansions or bottlenecks). In this study we provide the first genetic data on the critically endangered species the Reunion cuckoo-shrike Coracina newtoni. The Reunion cuckoo-shrike is a rare endemic forest bird surviving in a restricted 12-km(2) area of forested uplands and mountains. The total known population consists of less than one hundred individuals out of which 45 were genotyped using seventeen polymorphic microsatellite loci. We found a limited level of genetic variability and weak population structure, probably due to the limited geographic distribution. Using Bayesian methods, we identified a strong decline in population size during the Holocene, most likely caused by an ancient climatic or volcanic event around 5000 years ago. This result was surprising as it appeared in apparent contradiction with the accepted theory of recent population collapse due to deforestation and predator introduction. These results suggest that new methods allowing for more complex demographic models are necessary to reconstruct the demographic history of populations.     

Tropical forests and the changing earth system

Tropical forests are global epicentres of biodiversity and important modulators of the rate of climate change. Recent research on deforestation rates and ecological changes within intact forests, both areas of recent research and debate, are reviewed, and the implications for biodiversity (species loss) and climate change (via the global carbon cycle) addressed. Recent impacts have most likely been: (i) a large source of carbon to the atmosphere, and major loss of species, from deforestation and (ii) a large carbon sink within remaining intact forest, accompanied by accelerating forest dynamism and widespread biodiversity changes. Finally, I look to the future, suggesting that the current carbon sink in intact forests is unlikely to continue, and that the tropical forest biome may even become a large net source of carbon, via one or more of four plausible routes: changing photosynthesis and respiration rates, biodiversity changes in intact forest, widespread forest collapse via drought, and widespread forest collapse via fire. Each of these scenarios risks potentially dangerous positive feedbacks with the climate system that could dramatically accelerate and intensify climate change. Given that continued land-use change alone is already thought to be causing the sixth mass extinction event in Earth's history, should such feedbacks occur, the resulting biodiversity and societal consequences would be even more severe.     

Spatial and temporal deforestation dynamics in protected and unprotected dry forests: a case study from Myanmar (Burma)

Tropical dry forests are more threatened, less protected and especially susceptible to deforestation. However, most deforestation research focuses on tropical rain forests. We analyzed spatial and temporal changes in land cover from 1972 through 2005 at Chatthin Wildlife Sanctuary (CWS), a tropical dry forest in Myanmar (Burma). CWS is one of the largest protected patches of tropical dry forest in Southeast Asia and supports over half the remaining wild population of the endangered Eld’s deer. Between 1973 and 2005, 62% of forest was lost at an annual rate of 1.86% in the area, while forest loss inside CWS was only 16% (0.45% annually). Based on trends found during our study period, dry forests outside CWS would not persist beyond 2019, while forests inside CWS would persist for at least another 100 years. Analysis of temporal deforestation patterns indicates the highest rate of loss occurred between 1992 and 2001. Conversion to agriculture, shifting agriculture, and flooding from a hydro-electric development were the main deforestation drivers. Fragmentation was also severe, halving the area of suitable Eld’s deer habitat between 1973 and 2001, and increasing its isolation. CWS protection efforts were effective in reducing deforestation rates, although deforestation effects extended up to 2 km into the sanctuary. Establishing new protected areas for dry forests and finding ways to mitigate human impacts on existing forests are both needed to protect remaining dry forests and the species they support.     

Landscape history,calcareous fen development and historical events in the Slovak Eastern Carpathians

We explored interactions among human activities, landscape development and changes in biotic proxies in two small calcareous spring fens in the Slovak Eastern Carpathians. These date back to cal. a.d. 930. Results of pollen, plant macrofossil, and mollusc analyses were compared with the settlement history. The regional pollen record reflected historical events and changes in the settlement density very well at both study sites. The natural mixed fir-beech-spruce forests with fern undergrowth were suppressed and replaced by light-demanding trees in the periods of high human impact (e.g. Wallachian colonization). The study area was affected several times by wars and raids followed by a consequent decline in the settlement density. Some of these events are well reflected in the pollen records that document tree recovery and decline of cereals, weeds, and pasture indicators. In comparison, only some landscape changes were reflected in the local fen development. Both spring fens originated after deforestation, Ro?kovce around a.d. 1347 and Mirol'a around a.d. 929. The most pronounced change involving the water regime stabilization and undisturbed development of plant and mollusc communities took place after the decline in human impact. We conclude that humans were the main drivers of landscape transformation in the last millennium; they directly created spring-fen ecosystems through deforestation and influenced fen species composition through husbandry activities.     

Predicting the responsiveness of soil biodiversity to deforestation: a cross‐biome study

The consequences of deforestation for aboveground biodiversity have been a scientific and political concern for decades. In contrast, despite being a dominant component of biodiversity that is essential to the functioning of ecosystems, the responses of belowground biodiversity to forest removal have received less attention. Single‐site studies suggest that soil microbes can be highly responsive to forest removal, but responses are highly variable, with negligible effects in some regions. Using high throughput sequencing, we characterize the effects of deforestation on microbial communities across multiple biomes and explore what determines the vulnerability of microbial communities to this vegetative change. We reveal consistent directional trends in the microbial community response, yet the magnitude of this vegetation effect varied between sites, and was explained strongly by soil texture. In sandy sites, the difference in vegetation type caused shifts in a suite of edaphic characteristics, driving substantial differences in microbial community composition. In contrast, fine‐textured soil buffered microbes against these effects and there were minimal differences between communities in forest and grassland soil. These microbial community changes were associated with distinct changes in the microbial catabolic profile, placing community changes in an ecosystem functioning context. The universal nature of these patterns allows us to predict where deforestation will have the strongest effects on soil biodiversity, and how these effects could be mitigated.     

Assessing the impacts of past and ongoing deforestation on rainfall patterns in South America

Despite recent advances in modeling forest–rainfall relationships, the current understanding of changes in observed rainfall patterns resulting from historical deforestation remains limited. To address this knowledge gap, we analyzed how 40 years of deforestation has altered rainfall patterns in South America as well as how current Amazonian forest cover sustains rainfall. First, we develop a spatiotemporal neural network model to simulate rainfall as a function of vegetation and climate inputs in South America; second, we assess the rainfall effects of observed deforestation in South America during the periods 1982–2020 and 2000–2020; third, we assess the potential rainfall changes in the Amazon biome under two deforestation scenarios. We find that, on average, cumulative deforestation in South America from 1982 to 2020 has reduced rainfall over the period 2016–2020 by 18% over deforested areas, and by 9% over non-deforested areas across South America. We also find that more recent deforestation, that is, from 2000 to 2020, has reduced rainfall over the period 2016–2020 by 10% over deforested areas and by 5% over non-deforested areas. Deforestation between 1982 and 2020 has led to a doubling in the area experiencing a minimum dry season of 4 months in the Amazon biome. Similarly, in the Cerrado region, there has been a corresponding doubling in the area with a minimum dry season of 7 months. These changes are compared to a hypothetical scenario where no deforestation occurred. Complete conversion of all Amazon forest land outside protected areas would reduce average annual rainfall in the Amazon by 36% and complete deforestation of all forest cover including protected areas would reduce average annual rainfall in the Amazon by 68%. Our findings emphasize the urgent need for effective conservation measures to safeguard both forest ecosystems and sustainable agricultural practices.     

A bioregional analysis of the distribution of rainforest cover,deforestation and degradation in Papua New Guinea

Papua New Guinea (PNG) is an extensively forested country. Recent research suggests that despite commencing a trajectory of deforestation and degradation later than many counties in the Asia–Pacific region, PNG is now undergoing comparable rates of forest change. Here we explore the bioregional distribution of changes in the forest estate over the period 1972–2002 and examine their implications for forest protection. This is undertaken through the development of a novel bioregional classification of the country based on biogeographic regions and climatic zones, and its application to existing forest cover and forest‐cover change data. We found that degradation and deforestation varied considerably across the 11 defined biogeographic regions. We report that the majority of deforestation and degradation has occurred within all the lowland forests, and that it is these forests that have the greatest potential for further losses in the near term. The largest percentage of total change occurred in the east of PNG, in the islands and lowlands of the Bismarck, D'Entrecasteaux, East Papuan Islands and in the South‐East Papua–Oro region. The only region with a significant highlands component to undergo deforestation at a comparable magnitude to the islands and lowland regions was the Huon Peninsula and Adelbert region. Significant changes have also occurred at higher elevations, especially at the interface of subalpine grasslands and upper montane forests. Lower montane forests have experienced proportionally less change, yet it is these forests that constitute the majority of forests enclosed within the protected area system. We find that protected areas are not convincingly protecting either representative areas of PNG's ecosystems, nor the forests within their borders. We conclude by suggesting a more expansive and integrated approach to managing the national forest estate.     

Machine learning application to assess deforestation and wildfire levels in protected areas with tourism management

This study aims to identify the influence of management plans, management boards and tourism management on the relationship between performance indicators in the management of protected areas and degradation processes. To understand these relationships, 283 protected areas (PAs) in Brazil were analyzed. The first stage of the research used classification models based on machine learning algorithms, which revealed that predictive variables were a promising way to assess PAs vulnerability to deforestation and wildfire, giving decision-makers an 87.5% and 72.8% chance, respectively, of correctly identifying the PAs more susceptible to these threats. The predictive variables more relevant to deforestation were biome, area, and tourism management, while for wildfire, governance and PA type were the most relevant. Predictive variables were also a promising way to assess PAs management, giving decision-makers a 79.7% and 78.1% chance, respectively, to correctly identify the PAs with higher levels of effectiveness and governance. In addition, in the second stage, to empirically reinforce the models, multivariate analyses were performed, through which it was possible to confirm that deforestation levels are significantly higher in areas of sustainable use than in fully protected areas and determine how the positive interaction with tourism management contributes to the reduction in deforestation records and improves effectiveness. Therefore, it is understood that tourism management can strongly influence the sustainability of natural resources, and it is of utmost importance to generate tourism management policies with potential value generation for natural spaces.     

Effect of differential forest management on biodiversity in a tropical hill forest of Malaysia and implications for conservation

Forest ownership is considered as vital for sustainable management of forest and its associated biodiversity. The Global Forest Resources Assessment 2015 reported an increasing rate of privately owned forests on a global scale. However, deforestation was found to be very active in privately owned hill forest areas of Malaysia. Three forest reserves and three adjacent private forests from Penang State was purposively chosen as this state has been experiencing a quick and radical changes due to urban expansion over the last three decades. In this study variation in biodiversity were measured using community structure of both vascular plants and avifauna species along selected micro environmental variables. Finally implications for conservation were proposed considering the current state of deforestation in private hill forest (PHF). Plant community and avifauna analysis revealed that government hill forest areas (GHF) were more diverse and healthier than PHF, also rich with higher evenness. Species richness between GHF and PHF showed significant difference in plant species (p < 0.05) but not for avifauna. Avifauna diversity analysis recorded higher abundance of birds in PHF and finally appeared as buffer service provider for avifauna diversity in GHF reserves. But the current rate of deforestation in PHF is 1.4% annually. Thus any alteration to hill forest cover (land development activities) should be banned immediately with intensive care to the PHF through co-management. Moreover human activities inside the GHF should also be controlled to conserve the remnant species of the island as conspicuous disturbance were also found inside GHF.     

Moving forward socio‐economically focused models of deforestation

Whilst high‐resolution spatial variables contribute to a good fit of spatially explicit deforestation models, socio‐economic processes are often beyond the scope of these models. Such a low level of interest in the socio‐economic dimension of deforestation limits the relevancy of these models for decision‐making and may be the cause of their failure to accurately predict observed deforestation trends in the medium term. This study aims to propose a flexible methodology for taking into account multiple drivers of deforestation in tropical forested areas, where the intensity of deforestation is explicitly predicted based on socio‐economic variables. By coupling a model of deforestation location based on spatial environmental variables with several sub‐models of deforestation intensity based on socio‐economic variables, we were able to create a map of predicted deforestation over the period 2001–2014 in French Guiana. This map was compared to a reference map for accuracy assessment, not only at the pixel scale but also over cells ranging from 1 to approximately 600 sq. km. Highly significant relationships were explicitly established between deforestation intensity and several socio‐economic variables: population growth, the amount of agricultural subsidies, gold and wood production. Such a precise characterization of socio‐economic processes allows to avoid overestimation biases in high deforestation areas, suggesting a better integration of socio‐economic processes in the models. Whilst considering deforestation as a purely geographical process contributes to the creation of conservative models unable to effectively assess changes in the socio‐economic and political contexts influencing deforestation trends, this explicit characterization of the socio‐economic dimension of deforestation is critical for the creation of deforestation scenarios in REDD+ projects.     

Agricultural intensification increases deforestation fire activity in Amazonia

Fire-driven deforestation is the major source of carbon emissions from Amazonia. Recent expansion of mechanized agriculture in forested regions of Amazonia has increased the average size of deforested areas, but related changes in fire dynamics remain poorly characterized. We estimated the contribution of fires from the deforestation process to total fire activity based on the local frequency of active fire detections from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. High-confidence fire detections at the same ground location on 2 or more days per year are most common in areas of active deforestation, where trunks, branches, and stumps can be piled and burned many times before woody fuels are depleted. Across Amazonia, high-frequency fires typical of deforestation accounted for more than 40% of the MODIS fire detections during 2003–2007. Active deforestation frontiers in Bolivia and the Brazilian states of Mato Grosso, Pará, and Rondônia contributed 84% of these high-frequency fires during this period. Among deforested areas, the frequency and timing of fire activity vary according to postclearing land use. Fire usage for expansion of mechanized crop production in Mato Grosso is more intense and more evenly distributed throughout the dry season than forest clearing for cattle ranching (4.6 vs. 1.7 fire days per deforested area, respectively), even for clearings >200 ha in size. Fires for deforestation may continue for several years, increasing the combustion completeness of cropland deforestation to nearly 100% and pasture deforestation to 50–90% over 1–3-year timescales typical of forest conversion. Our results demonstrate that there is no uniform relation between satellite-based fire detections and carbon emissions. Improved understanding of deforestation carbon losses in Amazonia will require models that capture interannual variation in the deforested area that contributes to fire activity and variable combustion completeness of individual clearings as a function of fire frequency or other evidence of postclearing land use.     

Social Dimensions of Evolutionary Research: Discovering Native American History in Colonial Southeastern U.S.

Beginning in the late sixteenth century, a series of Spanish missions was built in coastal Georgia and northern Florida. These missions were designed to convert and “civilize” the indigenous peoples of the region and establish a Spanish presence in the southeastern United States. The colony was not a success, and the missions were destroyed by the English by 1706. The native population fared poorly and suffered massive loss of people due to epidemics and colonial period hardships. In this paper, I discuss microevolutionary analyses of archeological skeletal samples representing the native populations from the region. Analyses document changing patterns of variation and intergroup biological integration through time. Formal evolutionary interpretations are offered, but these are reinterpreted with respect to the social and historical context of the time period. Specifically, patterns of variation suggest a nascent Catholic Indian identity was emergent in Spanish Florida when the missions were destroyed. While this may indicate an evolutionary and historical “dead end” for the indigenous peoples of Florida, further interpretation of the data with respect to the later history of the early Seminole people suggests a continuous biological history can be inferred, linking Spanish period (seventeenth century) and Seminole period (eighteenth century) peoples of Florida within a unified historical narrative. This complex, ephemeral history has repercussions for interpreting evolutionary genetic data within a strict cladistic framework. In addition, this research contributes a humanistic component to the evolutionary sciences with respect to cultural patrimony and oral traditions, in this case, of the Seminole peoples.     

Mixing Carrots and Sticks to Conserve Forests in the Brazilian Amazon: A Spatial Probabilistic Modeling Approach

Annual forest loss in the Brazilian Amazon had in 2012 declined to less than 5,000 sqkm, from over 27,000 in 2004. Mounting empirical evidence suggests that changes in Brazilian law enforcement strategy and the related governance system may account for a large share of the overall success in curbing deforestation rates. At the same time, Brazil is experimenting with alternative approaches to compensate farmers for conservation actions through economic incentives, such as payments for environmental services, at various administrative levels. We develop a spatially explicit simulation model for deforestation decisions in response to policy incentives and disincentives. The model builds on elements of optimal enforcement theory and introduces the notion of imperfect payment contract enforcement in the context of avoided deforestation. We implement the simulations using official deforestation statistics and data collected from field-based forest law enforcement operations in the Amazon region. We show that a large-scale integration of payments with the existing regulatory enforcement strategy involves a tradeoff between the cost-effectiveness of forest conservation and landholder incomes. Introducing payments as a complementary policy measure increases policy implementation cost, reduces income losses for those hit hardest by law enforcement, and can provide additional income to some land users. The magnitude of the tradeoff varies in space, depending on deforestation patterns, conservation opportunity and enforcement costs. Enforcement effectiveness becomes a key determinant of efficiency in the overall policy mix.     

Palaeoecological investigations towards the reconstruction of the history of forest clearances and coastal heathlands in south-western Norway

Palynological data collected over a period of 60 years have been compiled and re-interpreted in order to reveal the patterns of deforestation and health establishment in the south-western Norwegian coastal heathland. This heathland area has been divided into four sub-regions based on topography, bedrock and drift cover. The palynological investigations are from sites with pollen source areas of different sizes. The palynological signals are interpreted in terms of models that suggest an abrupt, gradual or stepwise deforestation which can be explained by terms of different pollen source areas. The deforestation seems to have been metachronous, leading to a regional mosaic pattern of different vegetation types. The deforestation process spanned more than 3600 calendar years (4000-400 B.C.), with three pronounced clearance periods at 4000-3600 B.C. (Mesolithic/Early Neolithic transition), 2500-2200 B.C. (Middle Neolithic II/Early Late Neolithic transition), and 1900-1400 B.C. (Late Neolithic to Bronze Age period II). The expansion of heathland has also been metachronous and took place over a period of ca. 4000 years between 4000-200 B.C., but was mainly completed by the end of the Bronze Age. Regional differences in the chronology of deforestation and heathland establishment are discussed. Deforestation with subsequent heathland expansion can best be explained in terms of the interaction between land-use history, topography and edaphic conditions under climatic conditions that favoured heathland development.     

Testing an Ethnobiological Evolutionary Hypothesis on Plant-Based Remedies to Treat Malaria in Africa

The malaria hypothesis, which addresses a strong selective pressure on human genes resulting from a chain of processes that originated with the practice of agriculture, is an example of an evolutionary consequence of niche construction. This scenario has led us to formulate the following questions: Are the genetic adaptations of populations with a history of contact with malaria reflected in the local medical systems? Likewise, could environmental changes (deforestation) and the incidence of malaria result in an adaptive response in these local health care systems? We collected secondary data for the entire African continent from different databases and secondary sources and measured the response of health care systems as the variation in the richness of antimalarial medicinal plants. Our results did not indicate a cause-and-effect relationship between the tested variables and the medical systems, but a subsequent analysis of variance showed an increase in the mean of medicinal plants in regions with a higher incidence of malaria prior to disease control measures. We suggest that this response had a greater impact on local medical knowledge than other variables, such as genetic frequency and deforestation.     

Deforestation and sewage effects on aquatic macroinvertebrates in urban streams in Manaus,Amazonas, Brazil

In the last few years, awareness in developed countries has increased regarding the importance of urban watercourses as essential natural resources for human well being. Macroinvertebrates have been used as bioindicators to complement physico-chemical evaluation of water quality after environmental perturbations. The city of Manaus is closely associated with the Amazonian rain forest and with its dense hydrographic network. Any perturbation, such as deforestation and/or water pollution in the city’s streams, therefore causes changes in the local ecosystem as the population increases. In this study, 65 streams were sampled in October and November 2003. Samples were taken from stream-bed sediment in the center of the channel and litter/sediment at the edge of the stream. Deforestation, total Nitrogen (TN), total Phosphorus (TP), depth, width, electrical conductivity, temperature and dissolved Oxygen (DO) were measured. A total of 115,549 specimens were collected, distributed among 152 taxa. Oligochaeta, Chironomus, Psychodidae and Ceratopogonidae were the taxa with the greatest frequencies of occurrence and the highest total abundances. Higher deforestation, TN and TP were correlated with lower DO and greater electrical conductivity, pH and water temperature. Deforestation, TN and TP were not associated with water velocity and stream width. Depth was the only variable correlated (negatively) with deforestation and not correlated with TN and TP. Greater deforestation, TN and TP were correlated with lower richness of taxa; but these variables did not affect abundance. Canonical Correspondence Analysis ordenated the streams into two groups; the majority of the streams were in the group with high levels of deforestation and with high values of TP, TN, pH, electrical conductivity and temperature, where the macroinvertebrates were reduced to a few taxa. The other group was composed of streams that were well oxygenated and deep, where richness of taxa was higher. These results indicate changes in community composition in response to changes in environmental conditions. The highest taxa correlation was with streams that were well oxygenated and had the greatest depth and water velocity. Species Indicator Analysis identified 29 taxa as indicators of nonimpacted streams, 16 as indicators of deforested streams and three as indicators of streams impacted by deforestation and domestic sewage. Of the total sampled streams, 80% were impacted by deforestation and water pollution and had fauna tolerant of these perturbations. Water pollution, represented by TN and TP, affected the macroinvertebrate fauna in a way similar to deforestation, i.e., causing reduction in taxa richness, simplifying the insect community composition without changing abundance. Use of the taxa suggested in this study as environmental indicators could improve the evaluation of water quality in the streams in Central Amazonia. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. Handling editor: D. Dudgeon