RESUMO

Mangroves are among the most carbon-dense ecosystems on the planet. The capacity of mangroves to store and accumulate carbon has been assessed and reported at regional, national and global scales. However, small-scale sampling is still revealing 'hot spots' of carbon accumulation. This study reports one of these hotspots, with one of the largest-recorded carbon stocks in mangroves associated with sinkholes (cenotes) in the Yucatan Peninsula, Mexico. We assessed soil organic carbon (SOC) stocks, sequestration rates and carbon origin of deep peat soils (1 to 6 m). We found massive amounts of SOC up to 2792 Mg C ha-1, the highest value reported in the literature so far. This SOC is primarily derived from highly preserved mangrove roots and has changed little since its deposition, which started over 3220 years ago (±30 BP). Most cenotes are owned by Mayan communities and are threatened by increased tourism and the resulting extraction and pollution of groundwater. These hot spots of carbon sequestration, albeit small in area, require adequate protection and could provide valuable financial opportunities through carbon-offsetting mechanisms and other payments for ecosystem services.

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Mangroves are considered ideal ecosystems for Blue Carbon projects. However, because of their short stature, some mangroves ('scrub' mangroves, less than 2 m) do not fulfil the current definition of 'forests', which makes them ineligible for emission reduction programmes such as REDD+. Short stature mangroves can be the dominant form of mangroves in arid and nutrient-poor landscapes, and emissions from their deforestation and degradation could be substantial. Here, we describe a Blue Carbon project in the Gulf of California, Mexico, to illustrate that projects that avoid emissions from deforestation and degradation could provide financial resources to protect mangroves that cannot be included in other emission reduction programmes. The goal of the project is to protect 16 058 ha of mangroves through conservation concessions from the Mexican Federal Government. The cumulative avoided emissions of the project are 2.84 million Mg CO2 over 100 years, valued at $US 426 000 per year (US$15 per Mg CO2 in the California market). The funds could be used for community-based projects that will improve mangrove management, such as surveillance, eradication of invasive species, rehabilitation after tropical storms and environmental education. The strong institutional support, secure financial status, community engagement and clear project boundaries provide favourable conditions to implement this Blue Carbon project. Financial resources from Blue Carbon projects, even in mangroves of short stature, can provide substantial resources to enhance community resilience and mangrove protection.

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RESUMO

Selection of areas for restoration should be based on cost-effectiveness analysis to attain the maximum benefit with a limited budget and overcome the traditional ad hoc allocation of funds for restoration projects. Restoration projects need to be planned on the basis of ecological knowledge and economic and social constraints. We devised a novel approach for selecting cost-effective areas for restoration on the basis of biodiversity and potential provision of 3 ecosystem services: carbon storage, water depuration, and coastal protection. We used Marxan, a spatial prioritization tool, to balance the provision of ecosystem services against the cost of restoration. We tested this approach in a mangrove ecosystem in the Caribbean. Our approach efficiently selected restoration areas that at low cost were compatible with biodiversity targets and that maximized the provision of one or more ecosystem services. Choosing areas for restoration of mangroves on the basis carbon storage potential, largely guaranteed the restoration of biodiversity and other ecosystem services.

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En noviembre de 1983, se llevó a cabo una investigación sobre las condiciones de vida y la frecuencia de enfermedades transmisibles y de desnutrición en ocho campamentos de refugiados guatemaltecos y en tres comunidades rurales mexicanas en la frontera sur de México, con objeto de valorar si ha habido cambios en el perfil epidemiológico de la población mexicana de esa zona, debidos al impacto de la migración. Por muestreo aleatorio se seleccionaron 158 familias de refugiados guatemaltecos (955 individuos) y 125 familias de la población rural mexicana (718 individuos). Se aplicó un cuestionario, en el cual se registraron la composición de la familia y las características de las viviendas y se investigaron las enfermedades infecciosas mediante interrogatorio y exploración física detallada, registro de peso y talla, y toma de muestras de sangre y heces para búsqueda de Plasmodium y de parásitos intestinales. En ambos grupos de población las condiciones de vida eran deficientes, la mayoría de las viviendas carecían de agua entubada y las familias vivían en condiciones de hacinamiento. Se encontró una alta prevalencia de enfermedades infecciosas, en especial las transmitidas por contacto directo; 2,3% de los frotis de sangre fueron positivos para Plasmodium y la cobertura de vacunación de los niños menores de cinco años fue muy baja. Más del 80% de los individuos presentaron parasitosis intestinal y aproximadamente 75% de la población tenía algún grado de desnutrición. Se concluye que no ha habido un impacto importante de un grupo sobre otro, sino que las enfermedades que aquejan tanto a los refugiados guatemaltecos como a la población rural mexicana son las que prevalecen en la zona geográfica y están subordinadas a las condiciones socioeconómicas; por consiguiente, las medidas de control que se apliquen deberán incluir a ambos grupos de población

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Assuntos

RESUMO

In november 1983 a study was done of living conditions and the frequency of communicable diseases and malnutrition in eight camps for Guatemalan refugees and three rural Mexican communities along the southern border of Mexico. The purpose of the study was to determine what changes the influx of refugees might have brought about in the epidemiological profile of the Mexican population in that border zone. A study group of 158 Guatemalan refugee families (955 individuals) and 125 rural Mexican families (718 individuals) was selected by random sampling. A questionnaire was used to record the composition of the family and the characteristics of the dwellings, and the presence of infectious diseases was investigated by interviews, thorough physical examinations, recording of weights and heights, and examination of blood and feces for the presence of Plasmodium and intestinal parasites. In both population groups, living conditions were poor: most of the dwellings lacked running water and were overcrowed. The prevalence of infectious diseases, especially those transmitted by direct contact,was found to be high; 2.3 per cent of all blood smears tested positive for Plasmodium, and the vaccination coverage of children under 5 was very low. Intestinal parasitosis was found in more than 80 per cent of the individuals, and about 75 per cent of them suffered from some degree of malnutrition

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