Land use/land cover change and extreme climatic events in the arid and semi-arid ecoregions of Mexico

An index with the potential to integrate different climate hazards into a single parameter is required to guide preventive decision making. We integrated in a single index the degree of exposure to climate that the nation's municipalities have. We selected this spatial scale because the municipality is the basic unit of administrative and economic planning; consequently, this is the scale at which policies of adaptation to climate change must be fostered. We conceptualized exposure as the sum of historic extreme events, the degree of ecosystem conservation and current climate and its future scenarios. This approach allowed us to create a climate hazard exposure index at the municipality scale integrating past and present. Maps of this index can be constructed to serve as a medium of risk communication and to aid policy design. We used information from eighteen variables to statistically standardize and compute the hazard exposure index by applying empirical formulae. We found that actually, out of ten Mexicans, three live in flood-prone zones, three may suffer the passage of tropical cyclones, five reside in drought zones and two live in extreme drought regions. Additionally, hailstorms affect five out of ten Mexicans, while eight out of ten are affected by frosts. Incorporating climate change, in the future more municipalities and a higher population will live in high exposure. Because understanding exposure is a necessary prerequisite to understanding vulnerability, knowledge of the spatial distribution of exposure should be useful for reducing the identified climate hazard exposure and vulnerability to climate change.

The tropical rainforest is one of the lushest and most important plant communities in Mexico’s tropical regions, yet its potential distribution has not been studied in current and future climate conditions. The aim of this paper was to propose priority areas for conservation based on ecological niche and species distribution modeling of 22 species with the greatest ecological importance at the climax stage. Geographic records were correlated with bioclimatic temperature and precipitation variables using Maxent and Kuenm software for each species. The best Maxent models were chosen based on statistical significance, complexity and predictive power, and current potential distributions were obtained from these models. Future potential distributions were projected with two climate change scenarios: HADGEM2_ES and GFDL_CM3 models and RCP 8.5 W/m² by 2075–2099. All potential distributions for each scenario were then assembled for further analysis. We found that 14 tropical rainforest species have the potential for distribution in 97.4% of the landscape currently occupied by climax vegetation (0.6% of the country). Both climate change scenarios showed a 3.5% reduction in their potential distribution and possible displacement to higher elevation regions. Areas are proposed for tropical rainforest conservation where suitable bioclimatic conditions are expected to prevail.

In many countries, administrative and economic planning occurs at the municipality level. We believe that relevant policies for adapting to climate change can be initiated at this level. Thus, this article assesses the adaptive capacity of Mexican municipalities and populations to address climate change to measure the challenge that climate change represents. The method was developed as follows. We selected 19 indicators organized into four categories: human, social, financial, and natural. The information was standardized, and we used empirical formulas to obtain an adaptive capacity index. The index was mapped, and the distribution showed the spatial capacity for the adaptation of Mexican municipalities. We discuss the contributions these indicators made to the adaptive capacity and show that the human capital variables were the most relevant for defining the adaptive capacity of municipalities. We also applied this index to the observed climate exposure and sensitivity of Mexican municipalities to climate change. Thus, we propose a matrix to measure the dimensions of the challenges posed by climate change in terms of both decision-making and policy management for increasing the adaptive capacity of municipalities and populations within a nation.

La evapotranspiración potencial (ETP), así como la duración del periodo de crecimiento (PECRE), son indicadores esenciales de planif icación agrícola. Las agendas nacionales y locales deben considerar los escenarios del cambio climático y su impacto en evapotranspiración. El presente trabajo tuvo como objetivo analizar la distribución espacial de la ETP, el periodo de crecimiento en las condiciones climáticas actuales en todo el país y en escenarios de cambio climático, para contar con elementos técnicos suf icientes que permitan recomendar acciones de adaptación para la producción agrícola nacional. La ETP mensual se estimó a partir de la ETP de referencia (ET0) por el método de Penman-Monteith. Con este parámetro y la precipitación (P) media mensual se evaluó la fecha de inicio, f in y duración del periodo de crecimiento. Se estudiaron 28 escenarios de cambio climático para def inir la alteración de la ETP y su efecto en los PECRE de las zonas agrícolas del país. Se espera que la ETP aumente prácticamente en todo el territorio nacional como consecuencia del incremento generalizado de la temperatura y la disminución de la humedad relativa. Las clases de ETP menores de 1000 mm anuales disminuirán, mientras que las mayores a 1000 mm aumentarán en promedio 20% en el horizonte medio (2040-2069) y casi 50% hacia el horizonte lejano (2070-2099). Al considerar el cambio climático en el PECRE por estado, se observó que en tres de ellos (Baja California Sur, Coahuila y San Luís Potosí) no habría cambio respecto a las condiciones actuales. En el resto de los estados se reducirá el PECRE debido a una combinación de cambio en el inicio y el f inal del periodo de crecimiento. Los estudios cartográf icos permiten realizar el análisis espacial de los resultados, mismos que deben integrarse en la planif icación del uso agrícola del agua. Paralelamente hacen posible avanzar en el diseño de medidas de adaptación al cambio climático con un sólido fundamento técnico.