Extinction risk of Mesoamerican crop wild relatives

Ensuring food security is one of the world's most critical issues as agricultural systems are already being impacted by global change. Crop wild relatives (CWR)—wild plants related to crops—possess genetic variability that can help adapt agriculture to a changing environment and sustainably increase crop yields to meet the food security challenge. Here we report the results of an extinction risk assessment of 224 wild relatives of some of the world's most important crops (i.e. chilli pepper, maize, common bean, avocado, cotton, potato, squash, vanilla and husk tomato) in Mesoamerica—an area of global significance as a centre of crop origin, domestication and of high CWR diversity. We show that 35% of the selected CWR taxa are threatened with extinction according to The International Union for Conservation of Nature (IUCN) Red List demonstrates that these valuable genetic resources are under high anthropogenic threat. The dominant threat processes are land use change for agriculture and farming, invasive and other problematic species (e.g. pests, genetically modified organisms) and use of biological resources, including overcollection and logging. The most significant drivers of extinction relate to smallholder agriculture—given its high incidence and ongoing shifts from traditional agriculture to modern practices (e.g. use of herbicides)—smallholder ranching and housing and urban development and introduced genetic material. There is an urgent need to increase knowledge and research around different aspects of CWR. Policies that support in situ and ex situ conservation of CWR and promote sustainable agriculture are pivotal to secure these resources for the benefit of current and future generations

Regional scale effects of human density and forest disturbance on large-bodied vertebrates throughout the Yucatan Peninsula, Mexico

The occupancy probability of 35 large-bodied bird and mammal species was examined in relation to patch- and landscape-scale habitat and disturbance variables in 147 forest patches distributed throughout the Mexican Yucatán Peninsula. Occupancy was assessed on the basis of interviews with local informants. The most important predictors of vertebrate species richness, composition, and patch occupancy were human population density and the extent and quality of forest cover. Most forest species responded positively to forest extent, while felids in particular were sensitive to human population density. However, the effects of human density on patch occupancy operated at extremely local scales. Effects were stronger at a smaller grain size, offering optimistic prospects for conservation strategies that incorporate human population effects. Three arboreal frugivores (Ateles geoffroyi, Alouatta pigra, and Ramphastos sulfuratus) were strongly associated with total basal area of trees bearing fleshy fruits. The degree of hunting pressure was not related to human population density, and affected the occupancy probability of three game species, two of which (Mazama spp., Crax rubra) are among the most preferred prey across the Yucatán Peninsula. Levels of patch occupancy across this region varied considerably among species, and were best explained by body size and degree of forest habitat specificity, large-bodied species and habitat specialists being the most vulnerable. This study provides a quantitative assessment of the conservation potential of large vertebrates in Mesoamerica and identifies disturbance-sensitive species. This can inform regional-scale conservation planning at a time when low deforestation in parts of the Yucatán Peninsula still provides a narrow window of conservation opportunity given the rapid human population growth

Mesoamerica’s Crop Wild Relatives: A new approach for conservation planning

Crop wild relatives (CWR) are wild plants that are the ancestors of important crops for human well-being. CWR hold genetic diversity that can be vital for plant breeding programs and the sustainability of agriculture, particularly given global change. Conservation of CWR genetic diversity thus has become a global food security issue, and several countries are actively developing conservation strategies including the generation of a national checklist and inventory of CWR, the assessment of current threat status, the identification of knowledge and conservation, and the establishment of genetic reserves. In this context, Mexico, Guatemala, and El Salvador, in collaboration with experts abroad (University of Birmingham, UK, and IUCN), are working together in a project to contribute towards safeguarding Mesoamerican CWR (http://www.psmesoamerica.org/en/). One important step is to identify CWR conservation area networks framed within the systematic conservation planning approach. However, genetic diversity is generally not addressed during the planning process. As it is unfeasible to sample and perform genetic analyses of hundreds of species due to limited timeframes and conservation budgets, we propose a novel approach to overcome the lack of genetic data. We used two criteria to develop proxies for genetic diversity (PGD): environmental variability, as given by climate, soil and topographic spatially-defined variables; and historic differentiation, as shown by phylogeographic patterns found in other species of the same habitat and region. We tested our approach by using genomic data from an empirical study of maize wild relatives distributed in Mexico. By combining species distribution models of 120 Mesoamerican CWR taxa and 102 PGD, we delimited areas of potential population differentiation. Furthermore, we considered each taxon's IUCN Red List category and habitat preference, assessed by experts during the project, to determine areas for CWR conservation in Mexico, using the Zonation conservation planning tool. Areas identified as important for CWR in situ conservation are located within sites of high cultural diversity and in areas where agriculture originated and traditional agriculture is ongoing. Also, our study design maximizes the representation of CWR throughout its distribution, thus highlighting the need for comprehensive analysis to encompass the genetic variability of taxa. The results of this work represent a first national and regional guide to promote CWR in situ conservation and sustainable management that contributes towards achievement of the CBD Global Strategy for Plant Conservation, Sustainable Development Goals and Aichi Targets

Planning Landscape Connectivity in Mexico under Global Change

Climate change, habitat loss and fragmentation, invasive species, and resource over-exploitation are among the major factors driving biodiversity loss and the current global change crisis. Maintaining and restoring connectivity throughout fragmented landscapes is key to reduce habitat isolation and mitigate anthropogenic impacts. To date, few connectivity approaches seek to identify corridors along climate gradients and least transformed natural habitats despite its importance to facilitate dispersal of organisms, as species' ranges shift over time to track suitable climates. In this study, we identified least-cost climatic corridors in Mexico between 2027 old-growth vegetation patches incorporating evapotranspiration as climatic variable, Euclidean distances, and human impact. We identified old-growth vegetation patches using the land use and vegetation map of 2011 (scale 1:250 000) by the National Institute of Statistics and Geography (INEGI). Moreover, we calculated a human impact index based on the theoretical framework of the Global Biodiversity Model (Alkemade et al. 2009) but adapted for Mexico (Mexbio, Kolb 2016), and includes the impact of  land use, road infrastructure and fragmentation based on the land use and vegetation map of 2011 and a road map by the Mexican Institute of Transportation. We modeled corridors for a baseline period (1980-2009) and under three future time periods (2015-2039, 2045-2069 and 2075-2099), corresponding to four Global Circulation Models (MPI-ESM-LR, GFDL-CM3, HADGEM2-ES and CNRMCM5) each under two emission scenarios (RCP 4.5 and 8.5) The historical and future evapotranspiration values were calculated using the climate surfaces from Cuervo-Robayo et al. 2019 and from the Center of Atmospheric Sciences of the National Autonomous University of Mexico*1, respectively. The historical and future evapotranspiration values were calculated using the climate surfaces from Cuervo-Robayo et al. 2019 and from the Center of Atmospheric Sciences of the National Autonomous University of Mexico, respectively. We used the Turc evapotranspiration equation (Turc 1954)  to estimate actual evapotranspiration. Least cost climatic corridors using future climate projections were used to test the assumption that climatic gradients are maintained in the future. We then prioritized climatic corridors using a multicriteria analysis guided by expert knowledge, incorporating factors such as indicators of human impact, vulnerability and exposure to climate change, and priority sites for biodiversity conservation and restoration. On average, more than 4,500 least cost climatic corridors were identified for each scenario. There is a high spatial coincidence in the geographical location of current and future climatic corridors (overlap > 90%). Fewer corridors were identified in the northern part of the country where natural vegetation is less fragmented, whereas in central and southern Mexico landscape fragmentation is greater, resulting in an increased number of corridors (Fig. 1). The use of open spatial data was key in identifying climatic corridors in order to support decision-making. The results provide a spatial guide to implement conservation and restoration actions to promote connectivity, in particular among climatic stable areas, thus supporting the achievement of Aichi Targets and Sustainable Development Goals. Also, it informs multiple stakeholders and sectors in land-use planning decisions and to promote the alignment of existing incentives to reduce habitat loss, degradation and fragmentation in key areas needed to maintain and recover landscape connectivity in the face of global change