Habitat fragmentation and the desiccation of forest canopies: A case study from eastern Amazonia     

Gaël Briant  Susan G.W. Laurance 《Biological conservation》2010,143(11):2763-1997

Across the deforestation frontier in eastern Amazonia, we examined the relationship between edge-related forest desiccation and deforestation patterns using remote-sensing techniques. Canopy-moisture levels were estimated over an eight-year period in three study sites that encompassed ∼100,000 km² in area. We found four main effects of deforestation on dry-season canopy desiccation. First, intact forests showed no detectable change in canopy water content whereas forests adjacent to clearings showed significant water loss. Second, the distance to which edge-related desiccation penetrated into forest interiors varied among landscapes with differing forest loss and fragmentation. In moderately fragmented landscapes (with 65% and 51% remaining forest cover), canopy desiccation extended 1-1.5 km into forest interiors, whereas in heavily fragmented landscapes (20% forest cover) desiccation penetrated up to 2.7 km into forests. Third, the magnitude of edge-related desiccation varied among landscapes with differing fragmentation. Moderately fragmented landscapes exhibited a greater magnitude of change in canopy-water loss over the first 1 km from an edge than did heavily fragmented landscapes. Finally, forest desiccation penetrated further into forests over time in the moderately fragmented landscapes, but not in the heavily fragmented landscape, where edge-related desiccation had evidently ‘saturated’ remaining forests. We conclude that protracted dry seasons will have far more serious effects on fragmented than intact rainforests, with the former becoming highly vulnerable to destructive fires. With ∼30,000 km of new forest edge being created annually in Brazilian Amazonia, these finding have serious implications for forest conservation.  相似文献   

Water buffalo and cattle ranching in the Lower Amazon Basin: Comparisons and conflicts     

Pervaze A. Sheikh  Frank D. Merry  David G. McGrath 《Agricultural Systems》2006

From 1975 to 2000, the water buffalo population in the Brazilian Amazon increased at nearly 13% per year, making it one of the fastest growing herds in the world. On the floodplains of the Amazon River buffalo are managed in a similar manner to cattle, but often earn superior production figures. This production advantage, however, is tempered by the role buffalo play in conflicts between landowners; buffalo are prone to altering the floodplain environment and interfering with production activities such as fishing and farming. In this research, we show that buffalo are kept on the floodplains 24% longer than cattle throughout the year, and 37% longer than cattle during periods when landowner conflicts are most likely to occur. We also show that buffalo productivity is greater than cattle in this system, which gives an opportunity to design management regimes for buffalo that may increase production costs, but that will lower the environmental and social problems that involve buffalo. Specifically, when the waters begin to rise, buffalo should be removed from the floodplains at the same time as cattle. Although this will not lessen the damage done while the buffalo is on the floodplain, it will place buffalo on the floodplain during the dry season when the erosion potential is at its lowest, and reduce the time that buffalo may interfere with other production activities such as fishing. The additional production costs incurred by early removal will not dissipate the production advantage over cattle. Without specific management that addresses the socio-economic and environmental problems caused by buffalo, the continued high growth rate for the buffalo population on the Amazon floodplains may not be sustainable and conflicts will become commonplace.  相似文献   

The responses of understorey birds to forest fragmentation, logging and wildfires: An Amazonian synthesis     

J. Barlow  C.A. Peres  P.C. Stouffer  J.M. Wunderle 《Biological conservation》2006,128(2):182-192

We combine mist-net data from 24 disturbance treatments taken from seven studies on the responses of understorey Amazonian birds to selective logging, single and recurrent wildfires, and habitat fragmentation. The different disturbance treatments had distinct effects on avian guild structure, and fire disturbance and the isolation of forest patches resulted in bird communities that were most divergent from those in continuous, undisturbed forest in terms of their species composition. Although low-intensity logging treatments had the least noticeable effects, the composition of understorey birds was still markedly different from the composition in undisturbed forest. This analysis demonstrates the importance of preventing habitat fragmentation and the spread of fires in humid tropical forests, and highlights the need for more research to determine the long-term suitability of large areas of degraded forest for forest birds.  相似文献   

Change in Physical Properties of Ferralsols with Tree Planting in the Central Amazon, Brazil     

Keizo Hirai  Joãn Ferraz  Sávio F. Ferreira  Masahiro Kobayashi 《Soil Science and Plant Nutrition》2005,51(5):761-765

We examined the effects of mixed planting of fast growing tree species with indigenous Amazon tree species and soil tillage practices on soil physical properties in a deforested site used for agricultural cultivation. The site was located in the Central Amazon and consisted of Ferralsols. Bulk density and soil hardness were compared in the mixed planting site and an area where only indigenous tree species were planted. Many roots of the fast growing trees penetrated into the profile and caused changes in soil physical properties, i.e., decreasing bulk density and hardness. When tillage practices prior to planting were combined with mixed planting, the changes in soil physical properties were enhanced and the growth of not only the planted fast growing trees but also indigenous species such as mahogany, Swietenia macrophylla , which is shade tolerant, was accelerated.  相似文献   

Forest fragmentation differentially affects seed dispersal of large and small-seeded tropical trees     

Jennifer M. Cramer  Rita C.G. Mesquita 《Biological conservation》2007,137(3):415-423

The responses of plant-animal interactions to forest fragmentation can vary. We hypothesized that large-seeded plant species would be more susceptible to forest fragmentation than small-seeded species because large-seeded species rely on a few, extinction prone dispersers. We compared seed dispersal of the large-seeded, mammal dispersed Duckeodendron cestroides and the small-seeded, avian dispersed Bocageopsis multiflora. The number, percentage, distance, and distributions of dispersed seeds were all reduced in fragments for Duckeodendron but not for Bocageopsis. Other fragmentation research in tropical communities supports this hypothesis through three lines of evidence: (1) Large-seeded plant species are more prone to extinction, (2) Fragmentation restricts or alters the movement of large animal dispersers more than small dispersers, and (3) Large and small-seeded species seem to be differentially linked to primary and secondary forest habitats. Therefore, small-seeded plants may be more resilient to forest fragmentation while large-seeded species may be more susceptible and should be a priority for conservation.  相似文献   

Is higher-taxon analysis an useful surrogate of species richness in studies of Neotropical mammal diversity?     

Carlos Eduardo Viveiros Grelle 《Biological conservation》2002,108(1):101-106

The usefulness of higher-taxon analysis was investigated at genus-, family-, and order-levels; to estimate the species richness of mammals from localities in the Amazon and Central America. The dataset allowed the test of higher-taxon approach through all orders of mammals, and within the most speciose orders: Didelphimorphia, Chiroptera, Primates, and Rodentia. Analyses with all orders together, Didelphimorphia, Chiroptera, and Rodentia showed that family and order richness were not related with species richness. In all cases, there were significant and positive relationships between generic and species richness. Within Primates, family richness was related to the number of species, but weaker than the relationship between generic and species richness. In summary, higher-taxon approach, at the generic level, is a useful surrogate of species richness for mammals that occur in the Amazon and Central America.  相似文献   

Cattle are cash generating assets for mixed smallholder farms in the Eastern Amazon     

M. Siegmund-Schultze  B. Rischkowsky  J.B. da Veiga  J.M. King 《Agricultural Systems》2007

The presence of cattle in the Amazon region is controversial in terms of their ecological suitability and profitability compared with crops. Nevertheless, they are widely distributed in the study area in north-eastern Pará and, contrary to the common image of cattle on large ranches, a high proportion of them are kept on smallholder farms. To explain their presence, cattle are assumed to have benefits beyond physical production, such as complementing resource use or representing capital. To test this hypothesis, the costs and benefits of the three main agricultural activities, cattle, cassava and black pepper production, in terms of land, labour and capital productivity, were recorded in 37 small farms over a period of 15 months. To provide a longer perspective, benefits and costs of these activities were calculated for their assumed lifetime, which in the case of cattle, assumed a stable herd, derived from a deterministic herd model. The resultant values for land, labour and capital productivity of cattle were much lower than the values derived from direct observations during the study period, and were not as high as those for cassava and black pepper. Furthermore, the analysis of resource use in the farms showed that cattle production was not usually integrated with cropping activities, did not improve the use of available labour, and competed for land. Therefore, there had to be a reason for keeping cattle beyond their physical productivity. It was deduced to be their functional quality. Cattle could be disposed of quickly and easily at any time, in order to acquire large sums of cash or the equivalent in kind. The liquidity derived from keeping living stock was not matched by other agricultural activities or by the financial market. Hence, cattle turned out to be the best instrument of finance for the smallholder. Farmers were not interested in the continuous development of their herds, or sustainable production practices, and favoured low input management. Consequently, development plans relying on long-term, continuous commitments to pasture and cattle management are inappropriate. Instead, research and extension work should focus on simple, flexible and low-cost improvements to cattle keeping on crop-livestock smallholder farms, until credit programmes are available that replace the financing function of cattle.  相似文献   

Harvesting, local trade, and conservation of parrots in the Northeastern Peruvian Amazon     

José A González 《Biological conservation》2003,114(3):437-446

In some places of the northeastern Peruvian Amazon the harvesting and local trade of parrot nestlings is still a common practice (loreada) that takes place every year between February and April, despite being banned by the national laws. Between 1996 and 1999, I monitored the use of these birds in 3890-ha of Mauritia flexuosa-palm swamps, located close to the village of Victoria (Loreto, Peru). Seven species of parrots were collected by local poachers in the study area, with Amazona amazonica (61.1% of the captures) and Ara ararauna (25.9%) the most commonly harvested. The total number of nestlings taken during the 4-year study period was 1718, ranging from 680 birds harvested in 1996 to 166 in 1998. The two methods used to collect nestlings, cutting down the nesting tree or opening a hole in the trunk to reach the nest cavity, are not sustainable because nest-trees become useless and the next generation is completely removed. The analyses of demographic data and annual harvest rates suggest that at least three species (Ara ararauna, Ara macao and Amazona amazonica) are being over-harvested and may be seriously threatened in the long term.  相似文献   

A resource demand model of indigenous production: The Jivaroan cultivation systems of Western Amazonia     

Santiago López  Rodrigo Sierra 《Agricultural Systems》2011,104(3):246-257

This study examines the demand for land resources and agricultural production in the lower Pastaza River Basin of the Ecuadorian Amazon. Specifically, we concentrate on two territories controlled by Jivaroan indigenous groups. First, the analysis compares the structural characteristics of riverine and interfluvial cultivation systems in the region. Second, the study investigates the connections between agricultural intensity, population pressure and composition, and terrain conditions at the household level through the integration of geographic information systems, remote sensing, socio-economic surveys, and regression analyses. The study shows that although cultivation practices and the proportion between consumers and producers at the household level are not significantly different among riverine and interfluvial groups, riverine cultivators produce more intensively than interfluvial landholders. In general, the demand for agricultural production at a household level is positively correlated with population pressure and soil quality. In this region, the extent of cultivation is significantly associated with the proportion between consumers and producers along the household’s developmental cycle. These findings provide support for the view that land use intensification among indigenous peoples is similar to the dynamic among non-indigenous market-oriented producers.  相似文献   

From colonization to “environmental soy”: A case study of environmental and socio-economic valuation in the Amazon soy frontier     

Corrina Steward 《Agriculture and Human Values》2007,24(1):107-122

This paper examines the socio-economic and environmental implications of soy development in Santarém, Pará, located in the Brazilian Amazon. The settlement history of the region contributes directly to the way in which soy agriculture is currently proceeding in Santarém. Government policies and perspectives have been shaped by a history of agrarian colonization of Amazon forests, and the small farmers, or colonos, who are now being bought out by soy agribusiness are also rooted in this history. As a means of ascertaining the current state and interaction of soy actors with the burgeoning soy-based economy in the area, field research was conducted on the role of primary and secondary forests for soy production. Research also included an analysis of valuation discourses – that is, how the differing soy actors (local government, agribusiness, conservation NGOs, and small farmers) assign value to types of forests and their different interpretations of what constitutes environmental degradation. The ways in which these different actors assign such values to forests and how they structure the definition of environmental degradation is a key factor in determining who “wins” and “loses” in the realm of Amazon development. Significant environmental and socio-economic implications of soy expansion, especially for the colonos, are not taken into account because the dominant rhetoric of Amazonian development ignores their contribution to social and ecological diversity. This omission keeps colono communities living at poverty level and even exacerbates colono poverty under the soy development project. The colonos and their representatives are responding by setting forth their own, competing valuations of primary and secondary forests that contrast sharply with state soy growing schemes and NGO plans for “sustainable soy.” These have their roots in local knowledge and best practices. Corrina Steward is the Resource Rights Specialist at Grassroots International in Boston, Massachusetts. She holds a Masters degree in Environmental Science from the Yale School of Forestry and Environmental Studies in New Haven, Connecticut where she focused on social ecology, community development, and globalization. She recently co-edited the book Agroecology and the Struggle for Food Sovereignty in the Americas (2006, London, UK: International Institute for Environment and Development).  相似文献