Mangroves cover less than 0.1% of Earth's surface, store large amounts of carbon per unit area, but are threatened by global environmental change. The capacity of mangroves productivity could be characterized by their canopy greenness, but this property has not been systematically tested across gradients of mangrove forests and national scales. Here, we analyzed time series of Normalized Difference Vegetation Index (NDVI), mean air temperature and total precipitation between 2001 and 2015 (14 years) to quantify greenness and climate variability trends for mangroves not directly influenced by land use/land cover change across Mexico. Between 2001 and 2015 persistent mangrove forests covered 432 800 ha, representing 57% of the total current mangrove area for Mexico. We found a temporal greenness increase between 0.003 [0.001-0.004] and 0.004 [0.002-0.005] yr −1 (NDVI values±95%CI) for mangroves located over the Gulf of California and the Pacific Coast, with many mangrove areas dominated by Avicennia germinans. Mangroves developed along the Gulf of Mexico and Caribbean Sea did not show significant greenness trends, but site-specific areas showed significant negative greenness trends. Mangroves with surface water input have above ground carbon stocks (AGC) between 37.7 and 221.9 Mg C ha −1 and soil organic carbon density at 30 cm depth (SOCD) between 92.4 and 127.3 Mg C ha −1 . Mangroves with groundwater water input have AGC of 12.7 Mg C ha −1 and SOCD of 219 Mg C ha −1 . Greenness and climate variability trends could not explain the spatial variability in carbon stocks for most mangrove forests across Mexico. Site-specific characteristics, including mangrove species dominance could have a major influence on greenness trends. Our findings provide a baseline for national-level monitoring programs, carbon accounting models, and insights for greenness trends that could be tested around the world.
Resumen: En este trabajo se analizó el efecto de la extracción no controlada de madera sobre la comunidad y estructura de tamaños de los manglares de Alvarado. Para realizar ésto se muestrearon 15 sitios de los cuales se obtuvo la composición florística, altura y área basal. Los efectos sobre la estructura de tamaños se evaluaron con un análisis de la distribución de individuos por categoría de tallas. Se documentó la presencia de Avicennia germinans, Laguncularia racemosa y Rhizophora mangle. Los parámetros estructurales fueron similares a los registrados en otros manglares de la zona tropical de México; sin embargo, los sitios con mayor influencia humana presentan cambios en la dominancia de especies. El análisis por categoría de tamaños indica que L. racemosa tiene problemas de regeneración debido principalmente a la extracción de individuos < 10 cm de diámetro de tallo. Los datos sugieren que de continuar con la extracción actual de tallos de L. racemosa, la situación local de la especie puede estar en riesgo. Palabras clave: Avicennia germinans, categoría de tamaños diamétricos, extracción de madera, Laguncularia racemosa, Rhizophora mangle. Abstract:We analyzed the effects of uncontrolled timber extraction on community and diameter-size of mangroves in Alvarado. We sampled 15 sites, gathering data on floristic composition, height, and basal area. Changes in diameter-size were evaluated through the size-distribution analysis. Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle were present in the area. Structure parameters were similar to others documented in similar latitudes in Mexico, but the sites under human influence had shifts in species dominance. The analysis of diameter-size distributions indicated that L. racemosa was underrepresented due to logging, mainly of individuals < 10 cm in diameter. We suggest that current extraction trends threaten the distribution of L. racemosa.
Mangroves provide ecosystem services worth billions of dollars worldwide. Although countries with extensive mangrove areas implemented management and conservation programs since the 1980s, the global area is still decreasing. To recuperate this lost area, both restoration and rehabilitation (R/R) projects have been implemented but with limited success, especially at spatial scales needed to restore functional properties. Monitoring mangroves at different spatial scales in the long term (decades) is critical to detect potential threats and select cost-effective management criteria and performance measures to improve R/R program success. Here, we analyze the origin, development, implementation, and outcomes of a country-level mangrove monitoring system in the Neotropics covering >9000 km2 over 15 years. The Mexico’s Mangrove Monitoring System (SMMM) considers a spatiotemporal hierarchical approach as a conceptual framework where remote sensing is a key component. We analyze the role of the SMMM’s remote sensing products as a “hub” of multi- and interdisciplinary ecological and social-ecological studies to develop national priorities and inform local and regional mangrove management decisions. We propose that the SMMM products, outcomes, and lessons learned can be used as a blueprint in other developing countries where cost-effective R/R projects are planned as part of mangrove protection, conservation, and management programs.
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