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PubMed2002

Ozone dynamics and deposition processes at a deforested site in the Amazon basin.

The goal of this study is to investigate the impact of deforestation on ozone dynamics and deposition in the Brazilian Amazon basin. This goal is accomplished through i) analyses of ozone levels and deposition rates at a deforested site during the rainy season; and ii) comparisons of these data with similar information derived at a forest. At the pasture site maximum ozone mixing ratios reach 20 parts per billion on a volume basis (ppbv) but about 6 ppbv prevail over the forest. Maximum ozone deposition velocities for pastures can reach 0.7 cm s-1, which is about threefold lower than values derived for forests. Combining ozone abundance and deposition velocities, pasture maximum ozone fluxes reach approximately 0.2 microgram (ozone) m-2 s-1. This flux represents approximately 70% of the deposition rates measured over the forest. Hence, this study suggests that conversion of rainforests to pastures could lead to a net reduction (30%) in the ozone sink in the Amazon.

Agriculture↗
PubMed2006

Deforestation: risk of sex ratio distortion in hawksbill sea turtles.

Phenotypic sex in sea turtles is determined by nest incubation temperatures, with warmer temperatures producing females and cooler temperatures producing males. The common finding of highly skewed female-biased hatchling sex ratios in sea turtle populations could have serious repercussions for the long-term survival of these species and prompted us to examine the thermal profile of a relatively pristine hawksbill nesting beach in Guadeloupe, French West Indies. Data loggers placed at nest depth revealed that temperatures in the forested areas were significantly cooler than temperatures in the more open, deforested areas. Using these temperatures as a predictor of sex ratio, we were able to assess the relative contributions of the different beach zones to the primary sex ratio: significantly more males were likely to be produced in the forested areas. Coastal forests are therefore important male-producing areas for the hawksbill sea turtle, and this has urgent conservation implications. On Guadeloupe, as on many Caribbean islands, deforestation rates are high and show few signs of slowing, as there is continual pressure to develop beachfront areas. The destruction of coastal forest could have serious consequences both in terms of local nesting behavior and of regional demography through the effects on population sex ratios. Human alterations to nesting habitat in other reptile taxa have been shown to modify the thermal properties of nest sites in ways that can disrupt their ecology by allowing parasite transmission, increasing vulnerability to climate change, or rendering existing habitat unsuitable.

Animals↗
PubMed2002

Anthropogenic deforestation, El Niño and the emergence of Nipah virus in Malaysia.

In late 1998, a novel paramyxovirus named Nipah virus, emerged in Malaysia, causing fatal disease in domestic pigs and humans with substantial economic loss to the local pig industry. Pteropid fruitbats have since been identified as a natural reservoir host. Over the last two decades, the forest habitat of these bats in Southeast Asia has been substantially reduced by deforestation for pulpwood and industrial plantation. In 1997/1998, slash-and-burn deforestation resulted in the formation of a severe haze that blanketed much of Southeast Asia in the months directly preceding the Nipah virus disease outbreak. This was exacerbated by a drought driven by the severe 1997-1998 El Niño Southern Oscillation (ENSO) event. We present data suggesting that this series of events led to a reduction in the availability of flowering and fruiting forest trees for foraging by fruitbats and culminated in unprecedented encroachment of fruitbats into cultivated fruit orchards in 1997/1998. These anthropogenic events, coupled with the location of piggeries in orchards and the design of pigsties allowed transmission of a novel paramyxovirus from its reservoir host to the domestic pig and ultimately to the human population.

Animals↗
PubMed2006

The effect of deforestation on the human-biting rate of Anopheles darlingi, the primary vector of Falciparum malaria in the Peruvian Amazon.

To examine the impact of tropical rain-forest destruction on malaria, we conducted a year-long study of the rates at which the primary malaria vector in the Amazon, Anopheles darlingi, fed on humans in areas with varying degrees of ecological alteration in the Peruvian Amazon. Mosquitoes were collected by human biting catches along the Iquitos-Nauta road at sites selected for type of vegetation and controlled for human presence. Deforested sites had an A. darlingi biting rate that was more than 278 times higher than the rate determined for areas that were predominantly forested. Our results indicate that A. darlingi displays significantly increased human-biting activity in areas that have undergone deforestation and development associated with road development.

Animals↗
PubMed2006

Agriculture and deforestation in the tropics: a critical theoretical and empirical review.

Despite the important role that tropical forests play in human existence, their depletion, especially in the developing world, continue relentlessly. Agriculture has been cited as the major cause of this depletion. This paper discusses two main theoretical underpinnings for the role of agriculture in tropical deforestation. First, the forest biomass as input in agricultural production, and second, the competition between agriculture and forestry underlined by their relative marginal benefits. These are supported by empirical evidence from selected countries in Africa and South America. The paper suggests a need to find a win-win situation to control the spate of tropical deforestation. This may imply improved technologies in the agriculture sector in the developing world, which would lead both to increased production in the agriculture sector, and would also help control the use of tropical forest as an input in agriculture production.

Agriculture↗
PubMed1990

Decline in onchocerciasis in the eastern Usambara mountains, north eastern Tanzania, and its possible relationship to deforestation.

A survey to establish the extent and possible impact of deforestation and increased farming activities on the prevalence of onchocerciasis was carried out in all the 17 villages in the eastern Usambara mountains. Results revealed that the disease is widespread. Out of 2,968 inhabitants of all ages skin-snipped in 1984 in the area, 22.7% were positive for Onchocerca volvulus microfilariae. The infection rates in the under nineteen and under ten age groups were 10.3% and 6.6% respectively. The overall prevalence rose steadily with age, with the mean microfilarial density reaching a plateau at age 24. Of the population studied 35.4% were found to present with at least one clinical manifestation commonly associated with onchocerciasis. Visual impairment (9.4%) and blindness (0.1%) rates suggest that ocular onchocerciasis is not a health problem in the area at present. Comparison with results obtained in the area during the last survey show that during the past 25 years there has been a significant decline in prevalence of infection. This drop is thought to be due to the effects of extensive deforestation on the vector population. Control of transmission, which is likely to rise as a result of a re-afforestation programme in the area is discussed.

Adolescent↗
PubMed1990

Population decline of Simulium woodi and reduced onchocerciasis transmission at Amani, Tanzania, in relation to deforestation.

To investigate an apparent decline of the onchocerciasis vector Simulium woodi, in the Simulium neavei group, weekly 12-hour biting catches on man were carried out for 13 months near Amani and compared with those obtained 22 years earlier. The results showed a marked fall in biting S. neavei s.l. females and supported earlier findings on the aquatic stages. The mean biting-catch in 1985/6 was only 13% of that in 1963/4 and comprised 91% S. woodi and 9% the more common, but largely zoophilic, Simulium nyasalandicum (Amani form). The infection rate of S. woodi with Onchocerca volvulus larvae had also fallen markedly from 17% to 3% of parous flies; no S. nyasalandicum females were infected. Recent onchocerciasis surveys indicate that reduced transmission has resulted in lower infection rates in man. Exposure by deforestation of the breeding sites of S. woodi in small shaded streams seems to have caused the simuliid's population decline. Reduced populations of S. neavei group vector species have been reported in other deforested parts of eastern Africa. Our long-term quantitative data on declining numbers of biting females without control measures, help to corroborate such reports. Control may no longer be necessary in some areas allowing a greater concentration of limited resources.

Animals↗
PubMed2006

Long-term reduction of Trypanosoma cruzi infection in sylvatic mammals following deforestation and sustained vector surveillance in northwestern Argentina.

Long-term variations in the dynamics and intensity of sylvatic transmission of Trypanosoma cruzi were investigated around eight rural villages in the semiarid Argentine Chaco in 2002-2004 and compared to data collected locally in 1984-1991. Of 501 wild mammals from 13 identified species examined by xenodiagnosis, only 3 (7.9%) of 38 Didelphis albiventris opossums and 1 (1.1%) of 91 Conepatus chinga skunks were infected by T. cruzi. The period prevalence in opossums was four-fold lower in 2002-2004 than in 1984-1991 (32-36%). The infection prevalence of skunks also decreased five-fold from 4.1-5.6% in 1984-1991 to 1.1% in 2002-2004. Infection in opossums increased with age and from summer to spring in both study periods. The force of infection per 100 opossum-months after weaning declined more than six-fold from 8.2 in 1988-1991 to 1.2 in 2002-2004. Opossums were mainly infected by T. cruzi lineage I and secondarily by lineage IId in 1984-1991, and only by T. cruzi I in 2002-2004; skunks were infected by T. cruzi IId in 1984-1991 and by IIc in 2002-2004. The striking decline of T. cruzi infection in opossums and skunks occurred in parallel to community-wide insecticide spraying followed by selective sprays leading to very low densities of infected Triatoma infestans in domestic and peridomestic habitats since 1992; to massive deforestation around one of the villages or selective extraction of older trees, and apparent reductions in opossum abundance jointly with increases in foxes and skunks. These factors may underlie the dramatic decrease of T. cruzi infection in wild reservoir hosts.

Animal Diseases↗
PubMed2006

Deforestation and plant diversity of Madagascar's littoral forests.

Few studies have attempted to quantify the reduction or document the floristic composition of forests in Madagascar. Thus, we focused specifically on deforestation and plant diversity in Madagascar's eastern littoral community. We used a data set of approximately 13,500 specimen records compiled from both historical and contemporary collections resulting from recent intensive inventory efforts to enumerate total plant species richness and to analyze the degree of endemism within littoral forests. Change in littoral forest cover from original to current extent was estimated using geographical information systems tools, remote sensing data (satellite imagery and low-elevation digital photography), and environmental data layers. Of the original littoral forest only 10.3% remains in the form of small forest parcels, and only 1.5% of these remaining fragments are included within the existing protected-areas network. Additionally, approximately 13% of Madagascar's total native flora has been recorded from these forests that originally occupied <1% of its total land surface, and over 25% of the 1535 plant species known from littoral forests are endemic to this community. Given the ongoing pressure from human settlement along Madagascar's eastern coast, protection of the remaining forest fragments is critical for their survival. Fifteen of the largest intact littoral forest fragments we identified, collectively representing 41.5% of remaining littoral forest, are among priority sites recommended to the government of Madagascar for plant conservation and incorporation into the protected-areas network.

Biodiversity↗
PubMed2001

Climatic impact of tropical lowland deforestation on nearby montane cloud forests.

Tropical montane cloud forests (TMCFs) depend on predictable, frequent, and prolonged immersion in cloud. Clearing upwind lowland forest alters surface energy budgets in ways that influence dry season cloud fields and thus the TMCF environment. Landsat and Geostationary Operational Environmental Satellite imagery show that deforested areas of Costa Rica's Caribbean lowlands remain relatively cloud-free when forested regions have well-developed dry season cumulus cloud fields. Further, regional atmospheric simulations show that cloud base heights are higher over pasture than over tropical forest areas under reasonable dry season conditions. These results suggest that land use in tropical lowlands has serious impacts on ecosystems in adjacent mountains.

Altitude↗
PubMed2001

Indication of global deforestation at the Cretaceous-Tertiary boundary by New Zealand fern spike.

The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assemblages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by global wildfires.

Animals↗
PubMed2005

Bushmeat hunting, deforestation, and prediction of zoonoses emergence.

Understanding the emergence of new zoonotic agents requires knowledge of pathogen biodiversity in wildlife, human-wildlife interactions, anthropogenic pressures on wildlife populations, and changes in society and human behavior. We discuss an interdisciplinary approach combining virology, wildlife biology, disease ecology, and anthropology that enables better understanding of how deforestation and associated hunting leads to the emergence of novel zoonotic pathogens.

Animals↗