The expected impacts of sea level on the Mexican Atlantic coast.

The Mexican Atlantic coast is vulnerable to sea level rise due to its low, sandy shorelines with extensive adjacent wetlands. The increasing trends at the regional level are similar to global trends (~3 ± 0.04 mm/year): between 1.8 mm/year in Alvarado, Veracruz, to 3.6 mm/year in Isla Mujeres, Quintana Roo. A synthetic model was applied to Mexican Atlantic coast under two sea level rise scenarios for the year 2100. Our objectives were: 1) to identify potentially floodable zones in the face of a sea level rise of one and two meters on the Mexican Atlantic coast with a synthetic model using SRTM and LiDAR topographic data; 2) to determine vegetation and land use affected in the potentially floodable zones; and 3) quantify the vulnerable human population. With topographic data we identified low areas (one and two meters) to assess potentially floodable zones; these were intersected with data layers of vegetation, land use, and human population. Deltaic zones, coastal lagoons and low-lying areas of the Yucatan Peninsula were regions with the largest potentially floodable surface. In the one-meter sea rise scenario, 581,674 ha were identified as potentially floodable, and 896,151 in the two-meter scenario. The most vulnerable vegetation and land use types were wetlands, such as cattail marshes (tulares; ~29 %) and mangroves (~27 %), as well as cultivated grasslands (~6 %). The indirectly affected coastal population could be approximately 5.5 million in these scenarios (~33 %), and the directly affected population could range between 124,000 and 440,000 (~0.72 and 2.55 %, respectively). These results indicate that there will be strong effects in economic, social, and environmental impacts on the Atlantic coast of Mexico in the event of a one- and two-meters sea level rise. This type of work will enable proposal conservation and adaptation strategies for human populations and coastal cities.

Arsenic and mercury tolerant rhizobacteria that can improve phytoremediation of heavy metal contaminated soils.

Background: Mining deposits often contain high levels of toxic elements such as mercury (Hg) and arsenic (As) representing strong environmental hazards. The purpose of this study was the isolation for plant growth promoting bacteria (PGPBs) that can improve phytoremediation of such mine waste deposits. Methods: We isolated native soil bacteria from the rhizosphere of plants of mine waste deposits and agricultural land that was previously mine tailings from Tlalpujahua Michoacán, Mexico, and were identified by their fatty acid profile according to the MIDI Sherlock system. Plant growth promoting traits of all bacterial isolates were examined including production of 3-indoleacetic acid (IAA), siderophores, biofilm formation, and phosphate solubilization. Finally, the response of selected bacteria to mercury and arsenic was examined an in-vitro assay. Results: A total 99 bacterial strains were isolated and 48 identified, representing 34 species belonging to 23 genera. Sixty six percent of the isolates produced IAA of which Pseudomonas fluorescens TL97 produced the most. Herbaspirillum huttiense TL36 performed best in terms of phosphate solubilization and production of siderophores. In terms of biofilm formation, Bacillus atrophaeus TL76 was the best. Discussion: Most of the bacteria isolates showed high level of tolerance to the arsenic (as HAsNa2O4 and AsNaO2), whereas most isolates were susceptible to HgCl2. Three of the selected bacteria with PGP traits Herbispirillum huttiense TL36, Klebsiella oxytoca TL49 and Rhizobium radiobacter TL52 were also tolerant to high concentrations of mercury chloride, this might could be used for restoring or phytoremediating the adverse environmental conditions present in mine waste deposits.

Bee diversity in secondary forests and coffee plantations in a transition between foothills and highlands in the Guatemalan Pacific Coast.

BACKGROUND: Although conservation of pristine habitats is recognized in many countries as crucial for maintaining pollinator diversity, the contribution of secondary forest conservation is poorly recognized in the Latin American context, such as in Guatemala. San Lucas Tolimán (SLT) is a high-quality coffee production region from the Atitlan Province, which has the second highest deciduous forest cover in Guatemala and pristine forest is prioritized for conservation. In contrast, secondary forest protection is undetermined, since these forests are normally removed or strongly affected by coffee farming practices. This situation may affect the diversity of native pollinators, mainly bees, which usually rely on the secondary forest for food resources. METHODS: We conducted a study to investigate the importance of secondary forests around the SLT coffee plantations (Coffea arabica L.) for pollinators. We compared bee diversity (richness, abundance and composition) in secondary forests of different age and coffee plantations with diverse farming techniques. Being the first study of pollinators in Guatemalan coffee plantations, we also recorded data for an entire year (2013-2014) in order to describe bee seasonality. RESULTS: We found significant differences in bee diversity between the coffee plantations and secondary forests, particularly early secondary forests showed higher bee abundances but diversity indices were similar between different vegetation type plots. In the early dry season, secondary forests showed the greatest native bee diversity. During the late dry season, when the coffee was flowering, honey bees were dominant in the same plots. This study provides important management insights to support the conservation of pollinators, since our results offer guidelines to improve coffee production by increasing native pollinator diversity.

Suitable climatic habitat changes for Mexican conifers along altitudinal gradients under climatic change scenarios.

The high biodiversity of the Mexican montane forests is concentrated on the Trans-Mexican Volcanic Belt, where several Protected Natural Areas exist. Our study examines the projected changes in suitable climatic habitat for five conifer species that dominate these forests. The species are distributed sequentially in overlapping altitudinal bands: Pinus hartwegii at the upper timberline, followed by Abies religiosa, the overwintering host of the Monarch butterfly at the Monarch Butterfly Biosphere Reserve, P. pseudostrobus, the most important in economic terms, and P. devoniana and P. oocarpa, which are important for resin production and occupy low altitudes where montane conifers merge with tropical dry forests. We fit a bioclimatic model to presence-absence observations for each species using the Random Forests classification tree with ground plot data. The models are driven by normal climatic variables from 1961 to 1990, which represents the reference period for climate-induced vegetation changes. Climate data from an ensemble of 17 general circulation models were run through the classification tree to project current distributions under climates described by the RCP 6.0 watts/m2 scenario for the decades centered on years 2030, 2060 and 2090. The results suggest that, by 2060, the climate niche of each species will occur at elevations that are between 300 to 500 m higher than at present. By 2060, habitat loss could amount to 46-77%, mostly affecting the lower limits of distribution. The two species at the highest elevation, P. hartwegii and A. religiosa, would suffer the greatest losses while, at the lower elevations, P. oocarpa would gain the most niche space. Our results suggest that conifers will require human assistance to migrate altitudinally upward in order to recouple populations with the climates to which they are adapted. Traditional in situ conservation measures are likely to be equivalent to inaction and will therefore be incapable of maintaining current forest compositions.

Total Mercury in Plant Tissue from a Mining Landscape in Western Mexico.

Environmental impacts of mining activities are well known, particularly on-site degradation, but long term effects are less known. Mercury content from vegetation samples from a mine dump and surrounding forests was quantified for understanding the fate of this element in the local the environment. The study area, Tlalpujahua, Michoacán, México, has a mining history going back more than 400 years. Including gold and silver extraction by means of mercury amalgamation for 352 years (1554-1906). Mercury was present in all sampled materials. The highest values correspond to wood samples from the mine dump (13.84 ± 3.88 ppm), while wood samples from adjacent forests had 4.3 ± 2.4 ppm, almost twice as much as coniferous needles, shrub leaves and corn seeds (2.2 ± 0.34 ppm). The highest concentration was found for J. deppeana wood (16.05 ± 2.3 ppm). The capacity of accumulating mercury by Juniperus trees when growing on the mine dumps suggests that this species has a potential to be used for biosequestration purposes.

Biomonitors of atmospheric nitrogen deposition: potential uses and limitations.

Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha-1 year-1, well above the threshold for physiological damage of 12-20 kg of N ha-1 year-1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha-1 year-1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (-11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive monitoring is not feasible or can be complementary.

The thermal niche of Neotropical nectar-feeding bats: Its evolution and application to predict responses to global warming.

The thermal niche of a species is one of the main determinants of its ecology and biogeography. In this study, we determined the thermal niche of 23 species of Neotropical nectar-feeding bats of the subfamily Glossophaginae (Chiroptera, Phyllostomidae). We calculated their thermal niches using temperature data obtained from collection records, by generating a distribution curve of the maximum and minimum temperatures per locality, and using the inflection points of the temperature distributions to estimate the species optimal (STZ) and suboptimal (SRZ) zones of the thermal niche. Additionally, by mapping the values of the STZ and SRZ on a phylogeny of the group, we generated a hypothesis of the evolution of the thermal niches of this clade of nectar-feeding bats. Finally, we used the characteristics of their thermal niches to predict the responses of these organisms to climate change. We found a large variation in the width and limits of the thermal niches of nectar-feeding bats. Additionally, while the upper limits of the thermal niches varied little among species, their lower limits differ wildly. The ancestral reconstruction of the thermal niche indicated that this group of Neotropical bats evolved under cooler temperatures. The two clades inside the Glossophaginae differ in the evolution of their thermal niches, with most members of the clade Choeronycterines evolving "colder" thermal niches, while the majority of the species in the clade Glossophagines evolving "warmer" thermal niches. By comparing thermal niches with climate change models, we found that all species could be affected by an increase of 1°C in temperature at the end of this century. This suggests that even nocturnal species could suffer important physiological costs from global warming. Our study highlights the value of scientific collections to obtain ecologically significant physiological data for a large number of species.

Biological effects of carbon nanotubes generated in forest wildfire ecosystems rich in resinous trees on native plants.

Carbon nanotubes (CNTs) have a broad range of applications and are generally considered human-engineered nanomaterials. However, carbon nanostructures have been found in ice cores and oil wells, suggesting that nature may provide appropriate conditions for CNT synthesis. During forest wildfires, materials such as turpentine and conifer tissues containing iron under high temperatures may create chemical conditions favorable for CNT generation, similar to those in synthetic methods. Here, we show evidence of naturally occurring multiwalled carbon nanotubes (MWCNTs) produced from Pinus oocarpa and Pinus pseudostrobus, following a forest wildfire. The MWCNTs showed an average of 10 walls, with internal diameters of ∼2.5 nm and outer diameters of ∼14.5 nm. To verify whether MWCNT generation during forest wildfires has a biological effect on some characteristic plant species of these ecosystems, germination and development of seedlings were conducted. Results show that the utilization of comparable synthetic MWCNTs increased seed germination rates and the development of Lupinus elegans and Eysenhardtia polystachya, two plants species found in the burned forest ecosystem. The finding provides evidence that supports the generation and possible ecological functions of MWCNTs in nature.

Restoration planning to guide Aichi targets in a megadiverse country.

Ecological restoration has become an important strategy to conserve biodiversity and ecosystems services. To restore 15% of degraded ecosystems as stipulated by the Convention on Biological Diversity Aichi target 15, we developed a prioritization framework to identify potential priority sites for restoration in Mexico, a megadiverse country. We used the most current biological and environmental data on Mexico to assess areas of biological importance and restoration feasibility at national scale and engaged stakeholders and experts throughout the process. We integrated 8 criteria into 2 components (i.e., biological importance and restoration feasibility) in a spatial multicriteria analysis and generated 11 scenarios to test the effect of assigning different component weights. The priority restoration sites were distributed across all terrestrial ecosystems of Mexico; 64.1% were in degraded natural vegetation and 6% were in protected areas. Our results provide a spatial guide to where restoration could enhance the persistence of species of conservation concern and vulnerable ecosystems while maximizing the likelihood of restoration success. Such spatial prioritization is a first step in informing policy makers and restoration planners where to focus local and large-scale restoration efforts, which should additionally incorporate social and monetary cost-benefit considerations.

Potassium enhances frost tolerance in young individuals of three tropical dry forest species from Mexico.

Movement of species outside their range of distribution could be a strategy for conservation purposes, but before implementation, it is necessary to evaluate plants responses to the conditions that they will experience in new locations. We evaluated the effect of potassium fertilisation to enhance the frost tolerance of young individuals of Albizia plurijuga (Standley) Britton & Rose, Cedrela dugesii S.Watson and Ceiba aesculifolia (Kunth) Britten & Baker f., which are all common species from tropical dry forests in Mexico. Plants were propagated in a shade-house and fertilised during 9 months with different concentrations of potassium (39, 189 and 528ppm). In frost simulations, plants were exposed to temperatures below 0°C during different time periods and frost injury was assessed by electrolyte leakage of leaf discs from young and old leaves. We observed that potassium fertilisation enhanced frost tolerance by reducing electrolyte leakage mainly in young leaves. We recorded plant re-sprouting ability after exposure to subzero temperatures over 45 days, finding notable differences among species: all individuals of C. dugesii sprouted, followed by some of A. plurijuga and finally just one of C. aesculifolia. Also, high potassium levels increased re-sprouting response. These species have a low frost tolerance, but potassium fertilisation seemed to be effective to enhance it for young individuals, increasing the probability of survival if plants are moved to colder areas than current habitats.

Responses to simulated nitrogen deposition by the neotropical epiphytic orchid Laelia speciosa.

Potential ecophysiological responses to nitrogen deposition, which is considered to be one of the leading causes for global biodiversity loss, were studied for the endangered endemic Mexican epiphytic orchid, Laelia speciosa, via a shadehouse dose-response experiment (doses were 2.5, 5, 10, 20, 40, and 80 kg N ha(-1) yr(-1)) in order to assess the potential risk facing this orchid given impending scenarios of nitrogen deposition. Lower doses of nitrogen of up to 20 kg N ha yr(-1), the dose that led to optimal plant performance, acted as fertilizer. For instance, the production of leaves and pseudobulbs were respectively 35% and 36% greater for plants receiving 20 kg N ha yr(-1) than under any other dose. Also, the chlorophyll content and quantum yield peaked at 0.66 ± 0.03 g m(-2) and 0.85 ± 0.01, respectively, for plants growing under the optimum dose. In contrast, toxic effects were observed at the higher doses of 40 and 80 kg N ha yr(-1). The δ (13)C for leaves averaged -14.7 ± 0.2‰ regardless of the nitrogen dose. In turn, δ (15)N decreased as the nitrogen dose increased from 0.9 ± 0.1‰ under 2.5 kg N ha(-1)yr(-1) to -3.1 ± 0.2‰ under 80 kg N ha(-1)yr(-1), indicating that orchids preferentially assimilate NH4 (+) rather than NO3 (-) of the solution under higher doses of nitrogen. Laelia speciosa showed a clear response to inputs of nitrogen, thus, increasing rates of atmospheric nitrogen deposition can pose an important threat for this species.

Relationships between canopy complexity and germination microsites for Phalaris arundinacea L.

Microsites that prevent seed germination are critical for slowing the invasion of native plant communities by aggressive, clonal species. A suitable model for study is the clonal grass, Phalaris arundinacea, which reproduces prolifically from seed and is spreading into wetlands across temperate North America. Knowing that light conditions control its seed germination in the laboratory and that light varies with canopy complexity in a Wisconsin fen, we tested multiple attributes of microsites under spatially and temporally dynamic canopies (namely, presence/absence of a matrix species, number of species in the canopy, plus indirect effects of three soil water levels) for their control of germination in microcosms. Our 6-species canopies + the matrix of Glyceria striata had the densest cover and reduced P. arundinacea germination to 1.9%, compared to 7.3% for 1-species canopies + the matrix. After selectively removing canopy components, germination increased to 36.1% for 6-species and 33.0% for 1-species canopies. Comparing canopies with each of the six species, germination declined in relation to increasing leaf width. Given moist soil, P. arundinacea germination microsites are determined by canopy complexity, which affects light penetration, which in turn determines germination rate.