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Toledo-Aceves T.,Comision Nacional para el Conocimiento y Uso de la Biodiversidad CONABIO | Meave J.A.,National Autonomous University of Mexico | Gonzalez-Espinosa M.,Colegio de Mexico | Ramirez-Marcial N.,Colegio de Mexico
Journal of Environmental Management | Year: 2011

Tropical montane cloud forests (TMCF) are among the most threatened ecosystems globally in spite of their high strategic value for sustainable development due to the key role played by these forests in hydrological cycle maintenance and as reservoirs of endemic biodiversity. Resources for effective conservation and management programs are rarely sufficient, and criteria must be applied to prioritise TMCF for conservation action. This paper reports a priority analysis of the 13 main regions of TMCF distribution in Mexico, based on four criteria: (1) forest quality, (2) threats to forest permanence, (3) threats to forest integrity, and (4) opportunities for conservation. Due to the diverse socio-environmental conditions of the local communities living in Mexican TMCF regions, their associated social characteristics were also evaluated to provide a background for the planning of conservation actions. A set of indicators was defined for the measurement of each criterion. To assign priority values for subregions within each main region, an international team of 40 participants evaluated all the indicators using multicriteria decision-making analysis. This procedure enabled the identification of 15 subregions of critical priority, 17 of high priority, and 10 of medium priority; three more were not analysed due to lack of information. The evaluation revealed a number of subjects that had hitherto been undetected and that may prove useful for prioritisation efforts in other regions where TMCF is similarly documented and faces equally severe threats. Based on this analysis, key recommendations are outlined to advance conservation objectives in those TMCF areas that are subjected to high pressure on forest resources. © 2010 Elsevier Ltd. Source

Kolb M.,Comision Nacional para el Conocimiento y Uso de la Biodiversidad CONABIO | Mas J.-F.,National Autonomous University of Mexico | Galicia L.,National Autonomous University of Mexico
International Journal of Geographical Information Science | Year: 2013

Understanding and analysis of drivers of land-use and -cover change (LUCC) is a requisite to reduce and manage impacts and consequences of LUCC. The aim of the present study is to analyze drivers of LUCC in Southern Mexico and to see how these are used by different conceptual and methodological approaches for generating transition potential maps and how this influences the effectiveness to produce reliable LUCC models. Spatial factors were tested for their relation to main LUCC processes, and their importance as drivers for the periods 1993-2002 and 2002-2007 was evaluated by hierarchical partitioning analysis and logistic regression models. Tested variables included environmental and biophysical variables, location measures of infrastructure and of existing land use, fragmentation, and demographic and social variables. The most important factors show a marked persistence over time: deforestation is mainly driven by the distance of existing land uses; degradation and regeneration by the distance of existing disturbed forests. Nevertheless, the overall number of important factors decreases slightly for the second period. These drivers were used to produce transition potential maps calibrated with the 1993-2002 data by two different approaches: (1) weights of evidence (WoE) to represent the probabilities of dominant change processes, namely deforestation, forest degradation, and forest regeneration for temperate and tropical forests and (2) logistic RM that show the suitability regarding the different land-use and -cover (LUC) classes. Validation of the transition potential maps with the 2002-2007 data indicates a low precision with large differences between LUCC processes and methods. Areas of change evaluated by difference in potential showed that WoE produce transition potential maps that are more accurate for predicting LUCC than those produced with RM. Relative operating characteristic (ROC) statistics show that transition potential models based on RM do usually better predict areas of no change, but the difference is rather small. The poor performance of maps based on RM could be attributed to their too general representation of suitability for certain LUC classes when the goal is modeling complex LUCC and the LUC classes participate in several transitions. The application of a multimodel approach enables to better understand the relations of drivers to LUCC and the evaluation of model calibration based on spatial explanatory factors. This improved understanding of the capacity of LUCC models to produce accurate predictions is important for making better informed policy assessments and management recommendations to reduce deforestation. © 2013 Taylor & Francis. Source

Aguirre-Leon A.,Metropolitan Autonomous University | Perez-Ponce H.E.,Comision Nacional para el Conocimiento y Uso de la Biodiversidad CONABIO | Diaz-Ruiz S.,Metropolitan Autonomous University
Revista de Biologia Tropical | Year: 2014

The coastal lagoons of Veracruz, Gulf of Mexico, include a great variety of biological resources. These resources, especially fish communities, have been barely described and that require more ecological studies. With this aim, this investigation analyzed the spatial and temporal variation of diversity, abundance and assemblages of the fish community and its relationship with physicalchemical parameters of the Chica-Grande coastal system. For this, eight defined sites were monthly sampled for water characteristics and fish community composition (10min hauls of 1 500m2 a shrimp trawl net), between September 2005 and November 2006. The spatial-temporal variation of physical-chemical parameters, allowed the definition of two contrasting environments according to salinity, temperature, transparency, dissolved oxygen and depth gradients. A total of 1 947 fishes were collected for a total weight of 57.88kg. From these, 22 species, 20 genera and 14 families were identified; and four species were new records for the system. As it was detected for the physical-chemical conditions, the diversity of the fish community also showed a spatial gradient, with high values (H'=2.37, D=3.35, J'=0.82) in the brackish habitat, and low ones in freshwater environments. Fish abundance did not show such a marked gradient response, however, it was higher in the freshwater habitat. The highest diversity (H'=2.05) and species richness (D=2.99) was recorded during the North winds ("nortes") months (November-February), while density and biomass were higher (0.034 ind./m2, 1.42g/m2) during the rainy months (July-October). The Importance Value Index (IVI) defined six dominant species accounting for 77.8% of the fish abundance and 87.9% of total catch by weight. The Canonical Correspondence Analysis (CCA) showed that the fish-habitat relationship was explained by 68% of total variance for the two first axes, where salinity, transparency and temperature changes were the most important environmental variables in determining the fish community composition and distribution. In this study, spatial gradients of environmental variables explained the changes in fish species composition and abundance; while the temporal gradients, the fish community structure and its relationship with seasonal patterns of habitat use by the species during their life cycles. Source

Adame M.F.,Griffith University | Santini N.S.,University of Queensland | Tovilla C.,Colegio de Mexico | Vazquez-Lule A.,Comision Nacional para el Conocimiento y Uso de la Biodiversidad CONABIO | And 2 more authors.
Biogeosciences | Year: 2015

Riverine wetlands are created and transformed by geomorphological processes that determine their vegetation composition, primary production and soil accretion, all of which are likely to influence C stocks. Here, we compared ecosystem C stocks (trees, soil and downed wood) and soil N stocks of different types of riverine wetlands (marsh, peat swamp forest and mangroves) whose distribution spans from an environment dominated by river forces to an estuarine environment dominated by coastal processes. We also estimated soil C sequestration rates of mangroves on the basis of soil C accumulation. We predicted that C stocks in mangroves and peat swamps would be larger than marshes, and that C, N stocks and C sequestration rates would be larger in the upper compared to the lower estuary. Mean C stocks in mangroves and peat swamps (784.5 ± 73.5 and 722.2 ± 63.6 MgC ha-1, respectively) were higher than those of marshes (336.5 ± 38.3 MgC ha-1). Soil C and N stocks of mangroves were highest in the upper estuary and decreased towards the lower estuary. C stock variability within mangroves was much lower in the upper estuary (range 744-912 MgC ha−1) compared to the intermediate and lower estuary (range 537-1115 MgC ha-1) probably as a result of a highly dynamic coastline. Soil C sequestration values were 1.3 ± 0.2 MgC ha-1 yr-1 and were similar across sites. Estimations of C stocks within large areas need to include spatial variability related to vegetation composition and geomorphological setting to accurately reflect variability within riverine wetlands. © Author(s) 2015. Source

Kolb M.,Comision Nacional para el Conocimiento y Uso de la Biodiversidad CONABIO | Kolb M.,National Autonomous University of Mexico | Galicia L.,National Autonomous University of Mexico
Geographical Journal | Year: 2012

In the Neotropics increased rates of land use and land cover change (LULCC) and a strong deforestation trend in the second half of the twentieth century have caused environmental degradation and biodiversity loss. This study analysed patterns and processes of LULCC and deforestation for the Grijalva-Usumacinta watershed, one of the hydrologically and biologically most important watersheds in southern Mexico in face of the discussion about beginning forest transitions in the Neotropics. Maps of land use and land cover for 1992, 2002 and 2007 derived from satellite and aerial imagery were analysed to test the hypothesis of changing trends on a regional scale. Change rates and probabilities were calculated for two time periods and dominant LULCC processes were identified. LULCC is complex and cannot be explained by the predominant linear deforestation narrative alone. A crucial finding was an unusually high rate of forest degradation for all primary forest types, being 1.7 times the area of forest deforestation; and that deforestation processes occur mainly in secondary forests. Agricultural activities fostered by public policies are the principal drivers for LULCC, among which pastures have the highest impact on deforestation. Deforestation and LULCC rates and probabilities have stagnated, and natural reforestation has increased. Although these trends are essential for the onset of forest transition, deforestation and degradation outweigh by far vegetation regrowth. © 2011 The Authors. The Geographical Journal © 2011 Royal Geographical Society(with the Institute of British Geographers). Source

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