El Colegio de la Frontera Sur

Assessing Biodiversity Declines Understanding human impact on biodiversity depends on sound quantitative projection. Pereira et al. (p. 1496 , published online 26 October) review quantitative scenarios that have been developed for four main areas of concern: species extinctions, species abundances and community structure, habitat loss and degradation, and shifts in the distribution of species and biomes. Declines in biodiversity are projected for the whole of the 21st century in all scenarios, but with a wide range of variation. Hoffmann et al. (p. 1503 , published online 26 October) draw on the results of five decades' worth of data collection, managed by the International Union for Conservation of Nature Species Survival Commission. A comprehensive synthesis of the conservation status of the world's vertebrates, based on an analysis of 25,780 species (approximately half of total vertebrate diversity), is presented: Approximately 20% of all vertebrate species are at risk of extinction in the wild, and 11% of threatened birds and 17% of threatened mammals have moved closer to extinction over time. Despite these trends, overall declines would have been significantly worse in the absence of conservation actions.

Microplastics are emerging as a steadily increasing environmental threat. Wastewater treatment plants efficiently remove microplastics from sewage, trapping the particles in the sludge and preventing their entrance into aquatic environments. Treatment plants are essentially taking the microplastics out of the waste water and concentrating them in the sludge, however. It has become common practice to use this sludge on agricultural soils as a fertilizer. The aim of the current research was to evaluate the microplastic contamination of soils by this practice, assessing the implications of successive sludge applications by looking at the total count of microplastic particles in soil samples. Thirty-one agricultural fields with different sludge application records and similar edaphoclimatic conditions were evaluated. Field records of sludge application covered a ten year period. For all fields, historical disposal events used the same amount of sludge (40 ton ha−1 dry weight). Extraction of microplastics was done by flotation and particles were then counted and classified with the help of a microscope. Seven sludge samples were collected in the fields that underwent sludge applications during the study period. Soils where 1, 2, 3, 4, and 5 applications of sludge had been performed had a median of 1.1, 1.6, 1.7, 2.3, and 3.5 particles g−1 dry soil, respectively. There were statistical differences in the microplastic contents related to the number of applications that a field had undergone (1, 2, 3 < 4, 5). Microplastic content in sludge ranged from 18 to 41 particles g−1, with a median of 34 particles g−1. The majority of the observed microplastics were fibers (90% in sludge, and 97% in soil). Our results indicate that microplastic counts increase over time where successive sludge applications are performed. Microplastics observed in soil samples stress the relevance of sludge as a driver of soil microplastic contamination.

Plastic debris is widespread in the environment, but information on the effects of microplastics on terrestrial fauna is completely lacking. Here, we studied the survival and fitness of the earthworm Lumbricus terrestris (Oligochaeta, Lumbricidae) exposed to microplastics (Polyethylene, <150 μm) in litter at concentrations of 7, 28, 45, and 60% dry weight, percentages that, after bioturbation, translate to 0.2 to 1.2% in bulk soil. Mortality after 60 days was higher at 28, 45, and 60% of microplastics in the litter than at 7% w/w and in the control (0%). Growth rate was significantly reduced at 28, 45, and 60% w/w microplastics, compared to the 7% and control treatments. Due to the digestion of ingested organic matter, microplastic was concentrated in cast, especially at the lowest dose (i.e., 7% in litter) because that dose had the highest proportion of digestible organic matter. Whereas 50 percent of the microplastics had a size of <50 μm in the original litter, 90 percent of the microplastics in the casts was <50 μm in all treatments, which suggests size-selective egestion by the earthworms. These concentration-transport and size-selection mechanisms may have important implications for fate and risk of microplastic in terrestrial ecosystems.

Plastic residues have become a serious environmental problem in the regions with intensive use of plastic mulching. Even though plastic mulch is widely used, the effects of macro- and micro- plastic residues on the soil-plant system and the agroecosystem are largely unknown. In this study, low density polyethylene and one type of starch-based biodegradable plastic mulch film were selected and used as examples of macro- and micro- sized plastic residues. A pot experiment was performed in a climate chamber to determine what effect mixing 1% concentration of residues of these plastics with sandy soil would have on wheat growth in the presence and absence of earthworms. The results showed that macro- and micro- plastic residues affected both above-ground and below-ground parts of the wheat plant during both vegetative and reproductive growth. The type of plastic mulch films used had a strong effect on wheat growth with the biodegradable plastic mulch showing stronger negative effects as compared to polyethylene. The presence of earthworms had an overall positive effect on the wheat growth and chiefly alleviated the impairments made by plastic residues.

Abstract Although plastic pollution happens globally, the micro- (&lt;5 mm) and macroplastic (5–150 mm) transfer of plastic to terrestrial species relevant to human consumption has not been examined. We provide first-time evidence for micro- and macroplastic transfer from soil to chickens in traditional Mayan home gardens in Southeast Mexico where waste mismanagement is common. We assessed micro- and macroplastic in soil, earthworm casts, chicken feces, crops and gizzards (used for human consumption). Microplastic concentrations increased from soil (0.87 ± 1.9 particles g −1 ), to earthworm casts (14.8 ± 28.8 particles g −1 ), to chicken feces (129.8 ± 82.3 particles g −1 ). Chicken gizzards contained 10.2 ± 13.8 microplastic particles, while no microplastic was found in crops. An average of 45.82 ± 42.6 macroplastic particles were found per gizzard and 11 ± 15.3 macroplastic particles per crop, with 1–10 mm particles being significantly more abundant per gizzard (31.8 ± 27.27 particles) compared to the crop (1 ± 2.2 particles). The data show that micro- and macroplastic are capable of entering terrestrial food webs.

Abstract This is the third compilation of imperiled (i.e., endangered, threatened, vulnerable) plus extinct freshwater and diadromous fishes of North America prepared by the American Fisheries Society'S Endangered Species Committee. Since the last revision in 1989, imperilment of inland fishes has increased substantially. This list includes 700 extant taxa representing 133 genera and 36 families, a 92% increase over the 364 listed in 1989. The increase reflects the addition of distinct populations, previously non-imperiled fishes, and recently described or discovered taxa. Approximately 39% of described fish species of the continent are imperiled. There are 230 vulnerable, 190 thretened, and 280 endangered extant taxa, and 61 taxa presumed extinct or extirpated from nature. Of those that were imperiled in 1989, most (89%) are the same or worse in conservation status; only 6% have improved in status, and 5% were delisted for various reasons. Habitat degradation and nonindigenous species are the main threats to at-risk fishes, many of which are restricted to small ranges. Documenting the diversity and status of rare fishes is a critical step in identifying and implementing appropriate actions necessary for their protection and management.

Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km(2) of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.

Plastic residues could accumulate in soils as a consequence of using plastic mulching, which results in a serious environmental concern for agroecosystems. As an alternative, biodegradable plastic films stand as promising products to minimize plastic debris accumulation and reduce soil pollution. However, the effects of residues from traditional and biodegradable plastic films on the soil-plant system are not well studied. In this study, we used a controlled pot experiment to investigate the effects of macro- and micro- sized residues of low-density polyethylene and biodegradable plastic mulch films on the rhizosphere bacterial communities, rhizosphere volatile profiles and soil chemical properties. Interestingly, we identified significant effects of biodegradable plastic residues on the rhizosphere bacterial communities and on the blend of volatiles emitted in the rhizosphere. For example, in treatments with biodegradable plastics, bacteria genera like Bacillus and Variovorax were present in higher relative abundances and volatile compounds like dodecanal were exclusively produced in treatment with biodegradable microplastics. Furthermore, significant differences in soil pH, electrical conductivity and C:N ratio were observed across treatments. Our study provides evidence for both biotic and abiotic impacts of plastic residues on the soil-plant system, suggesting the urgent need for more research examining their environmental impacts on agroecosystems.

Microplastic pollution is becoming a major challenge with the growing use of plastic. In recent years, research about microplastic pollution in the environment has become a field of study with increased interest, with ever expanding findings on sources, sinks and pathways of microplastics. Wastewater treatment plants effectively remove microplastics from wastewater and concentrate them in sewage sludge which is often used to fertilise agricultural fields. Despite this, quantification of microplastic pollution in agricultural fields through the application of sewage sludge is largely unknown. In light of this issue, four wastewater treatment plants and 16 agricultural fields (0–8 sewage sludge applications of 20–22 tons ha−1 per application), located in the east of Spain, were sampled. Microplastics were extracted using a floatation and filtration method, making a distinction between light density microplastics (ρ < 1 g cm−3) and heavy density microplastics (ρ > 1 g cm−3). Sewage sludge, on average, had a light density plastic load of 18,000 ± 15,940 microplastics kg−1 and a heavy density plastic load of 32,070 ± 19,080 microplastics kg−1. Soils without addition of sewage sludge had an average light density plastic load of 930 ± 740 microplastics kg−1 and a heavy density plastic load of 1100 ± 570 microplastics kg−1. Soils with addition of sewage sludge had an average light density plastic load of 2130 ± 950 microplastics kg−1 and a heavy density plastic load of 3060 ± 1680 microplastics kg−1. On average, soils’ plastic loads increased by 280 light density microplastics kg−1 and 430 heavy density microplastics kg−1 with each successive application of sewage sludge, indicating that sewage sludge application results in accumulation of microplastics in agricultural soils.

Strong decreases in greenhouse gas emissions are required to meet the reduction trajectory resolved within the 2015 Paris Agreement. However, even these decreases will not avert serious stress and damage to life on Earth, and additional steps are needed to boost the resilience of ecosystems, safeguard their wildlife, and protect their capacity to supply vital goods and services. We discuss how well-managed marine reserves may help marine ecosystems and people adapt to five prominent impacts of climate change: acidification, sea-level rise, intensification of storms, shifts in species distribution, and decreased productivity and oxygen availability, as well as their cumulative effects. We explore the role of managed ecosystems in mitigating climate change by promoting carbon sequestration and storage and by buffering against uncertainty in management, environmental fluctuations, directional change, and extreme events. We highlight both strengths and limitations and conclude that marine reserves are a viable low-tech, cost-effective adaptation strategy that would yield multiple cobenefits from local to global scales, improving the outlook for the environment and people into the future.

The major challenge in tropical land management is to meet the ever-growing demand for agricultural products while conserving biodiversity, providing critical ecosystem services, and maintaining rural livelihoods. This challenge is particularly acute in the Mesoamerican biodiversity hotspot, a region of high conservation value for both wild and domesticated species that is undergoing rapid human population growth, ecological degradation, and loss of traditional farming systems (Myers et al. 2000; Harvey et al. 2005a). Approximately 80% of the region's vegetation has been converted to agriculture, threatening biodiversity. More than 300 of the region's endemic species of flora and fauna are threatened, including at least 107 that are critically endangered (CI 2007). With continuing habitat loss (deforestation is 1.2%/year in Central America and Mexico combined; FAO 2005) and fragmentation of remaining forests, pressure on the region's biodiversity will intensify. Habitat destruction and fragmentation are not the only drivers of biodiversity loss in the region, however. Globalization of market forces, agricultural industrialization, migration, public policy, and cultural changes are driving the transformation of diverse, traditional, smallholder agroecosystems into agroindustrial systems dependent on chemical inputs and mechanization (Conway & Rosset 1996; Perfecto et al. 1996; Angelsen & Kaimowitz 2001). Agroindustrial intensification is often accompanied by significant reductions in tree cover, fallow vegetation, habitat diversity, and forest connectivity. These transformations directly threaten species dependent on natural habitat and undermine indigenous management practices that coevolved with this biodiversity for over 10,000 years (Nigh & Levy Tacher 2008). Despite considerable efforts to protect biodiversity in reserves and parks in Mesoamerica, many of these refuges are small, fragmented, isolated, or poorly protected (Miller et al. 2001), and not all ecosystems or species are represented adequately (Powell et al. 2000; Rodrigues et al. 2004). Besides having inadequate dimensions, most protected areas are embedded within an agricultural landscape, and existing buffer zones are inadequate to alleviate effects of fragmentation, contamination by agrochemicals, hunting, and unsustainable or illegal logging (DeFries et al. 2005). The fate of biodiversity within protected areas is therefore inextricably linked to the broader landscape context, including how the surrounding agricultural matrix is designed and managed (Wallace et al. 2005; Vandermeer et al. 2007). Protecting biodiversity while sustaining agricultural productivity, indigenous cultures, and rural livelihoods, requires a new approach to conservation, particularly in regions such as Mesoamerica, where substantial habitat conversion has already occurred. In contrast to the prevailing trend of managing protected areas and productive lands separately, we propose integrated landscape management in which conservation and production units within the agricultural matrix are managed jointly for long-term sustainability. We do not advocate agricultural intensification to spare further forest conversion (e.g., Green et al. 2005) because this approach is unlikely to have the intended outcome, for reasons discussed elsewhere (Vandermeer & Perfecto 2005, 2007; Matson & Vitousek 2006). Instead conservation efforts should be based on the recognition that how agriculture is conducted and how different land uses are distributed spatially and temporally determine the region's biodiversity (Perfecto & Vandermeer 1997; McNeely & Scherr 2003). Lasting conservation will therefore require alliances among conservation biologists, farmers, and land managers to actively plan the future of Mesoamerican landscapes. Here we use an integrated landscape approach to highlight opportunities for achieving long-term conservation in Mesoamerica. We provide an overview of the potential for agricultural landscapes and traditional smallholder farming to conserve biodiversity, propose an urgent action agenda to guide conservation in agricultural landscapes and stem the loss of biodiversity and traditional farming systems, and outline key socioeconomic, legal, and political conditions needed for successful implementation of the action plan. Although our examples and recommendations focus on Mesoamerica, our approach is relevant to other regions where there are similar challenges to conserving biodiversity in human-modified landscapes. An increasing number of studies in Mesoamerica show that certain agricultural landscapes and traditional smallholder practices contribute to biodiversity conservation (e.g., Estrada & Coates-Estrada 2002; Daily et al. 2003; Mayfield & Daily 2005) and at the same time contribute to increased food production and rural income (Pretty et al. 2003). In particular, heterogeneous agricultural landscapes that retain abundant tree cover (as forest fragments, fallows, riparian areas, live fences, dispersed trees, or shade canopies) provide complementary habitats, resources, and landscape connectivity for a significant portion of the original biota (e.g., Harvey et al. 2006a; Sekercioglu et al. 2007). Landscape configurations that connect forest patches, maintain a diverse array of habitats, and retain high structural and floristic complexity generally conserve more species than landscapes lacking connectivity or habitat complexity (Benton et al. 2003; Bennett et al. 2006). In addition, agricultural landscapes with abundant tree cover serve as buffers for remaining natural areas (Wallace et al. 2005) and contribute regionally to the maintenance of important ecosystem services, such as natural pest management, carbon sequestration, and water and soil conservation (Daily 1997; Soto-Pinto et al. 2002). Within agricultural landscapes, forested and nonforested habitats contribute to biodiversity conservation. Forest fragments, riparian forests, tree plantations, and other types of remnant and introduced tree cover serve as habitats for many species, enhance landscape connectivity, and retain potential for forest regeneration and restoration (Chazdon 2003; Harvey et al. 2006a). Nevertheless, other types of land uses, such as diverse coffee agroforestry (e.g., Moguel & Toledo 1999; Komar 2006), cocoa agroforestry (Rice & Greenberg 2000; Harvey et al. 2006b), silvopastoral systems (Harvey et al. 2005b, 2006a), and traditional agroecological land uses (such as diverse polycultures, organic farming, and swidden agriculture; Finegan & Nasi 2004) also harbor high levels of both wild and agricultural biodiversity and offer much greater conservation value than the agroindustrial systems that typically replace them. In general, biodiversity-friendly land uses are those that mimic the structural and floristic diversity of native vegetation and rely the least on agrochemicals (Tscharntke et al. 2005). The diverse agroecology systems and landscapes described above are typically (but not always) managed by smallholders (campesinos) and indigenous farmers. Although most environmentally friendly farming practices are not scale-specific in principle, landscapes that are composed of many small farms often demonstrate a high potential for sustaining both biodiversity and rural livelihoods (Rosset 1999). Small farmers are more likely to know their land intimately, embrace complexity and multifunctionality, retain multiple traditional varieties, focus on inputs of knowledge and labor rather than purchased agrochemicals and mechanization, and grow food for nearby consumption instead of commodities for export (Netting 1993; Nazarea 2006). Thus, conservation of biodiversity will often be well served by policies that favor smallholders, promote diverse farming landscapes, and support dissemination of traditional practices and agroecological knowledge (Castillo & Toledo 2000). On the basis of existing evidence and experiences, we propose an action agenda to seize opportunities to reconcile farming and biodiversity conservation and to respond to the immediate threats of biodiversity loss and unsustainable farming. The goal of the action agenda is to achieve sustainable and resilient landscapes in which conservation and agricultural production objectives are accomplished in mutually reinforcing ways. The specific conservation goals are to conserve plant and animal biodiversity; maintain intact habitats, ecological communities, and ecosystem functions; buffer existing protected areas; maintain landscape connectivity; and retain landscape resilience to disturbance and climate change. The agricultural goals are to fulfill human livelihood needs, sustain yields, conserve indigenous and smallholder agroecosystems and associated knowledge and culture, diversify products, minimize reliance on external inputs, and reduce vulnerability to natural disasters and climate change. Our action agenda contains six strategies (Table 1). The first consists of working with stakeholders in a participatory approach to identify priority landscapes where action for conservation and agricultural sustainability will bring the greatest results. Numerous tools already identify areas with high conservation value and the greatest need for protection (e.g., key biodiversity areas [Eken et al. 2004] and priority ecoregions [Olson & Dinerstein 2002]), but these tools rarely include information on rural livelihoods and agricultural systems. We advocate combining the analysis of biodiversity hotspots (Myers et al. 2000) with the identification of rural hotspots, where traditional smallholder livelihoods are most vulnerable and where agroecological systems and knowledge are being rapidly lost. This approach would allow the identification of landscapes where conservation priorities and rural development priorities overlap and where integration is most likely to succeed. Landscapes that are likely to emerge as priorities include those located near protected areas or in key biological corridors, those that conserve high diversity of traditional and indigenous crops, and those with high forest and tree cover that are being rapidly encroached upon by intensive agriculture or urbanization. In contrast, agricultural landscapes that are already dominated by agroindustrial production (such as industrially grown sugarcane, pineapple, or banana) are less likely to warrant attention because the chances of reconciling farming and biodiversity conservation there are slim. The second strategy is to address major threats to biodiversity within priority landscapes. Common threats include illegal logging, irresponsible use of agrochemicals, forest degradation by cattle grazing, shortening of fallows, unsustainable collection of firewood and other products, and conversion of diversified agricultural systems to agroindustrial monocultures with low biodiversity value (Carrillo & Vaughan 1994; Harvey et al. 2005a). Measures should be taken to mitigate these threats. For example, planting multipurpose trees on farms offers an alternative to firewood extraction from native forests (Barrance & Hellin 2003); integrated fire management (including prescribed burns, establishment of fire breaks, and training in sensible fire use) reduces unintended burning of native forests (Myers 2006); and adopting organic practices and integrated pest management can reduce dependence on pesticides (Kogan 1998; Morales & Perfecto 2000). Nevertheless, these promising approaches need to be applied systematically over large areas, with active participation and leadership of local rural communities (Nelson 1994). The protection of remaining native habitat (whether intact forest, wetland, or grassland) constitutes the third key strategy for conserving biodiversity and maintaining rural livelihoods in agricultural landscapes. Native habitat protection should continue to form the cornerstone of conservation activities because they provide resources to native species, maintain intact ecological communities, serve as genetic sources for recolonization of the agricultural matrix, and buffer against extreme weather events and climate change (Bengtsson et al. 2003; Taberelli & Gascon 2005). Large, contiguous areas of native habitat and vegetation along riparian areas (that form natural corridors) are of particularly high conservation value and should be priorities. Nevertheless, even small (<5 ha) and degraded forest patches can be important for some species, providing additional resources and landscape connectivity (Sekercioglu et al. 2007). Protecting native habitats within the agricultural landscape also benefits rural communities by providing products and ecosystem services such as pollination, pest management, flood control, and nutrient cycling on which agricultural systems (and farmers) depend (Ricketts 2004; Naidoo & Ricketts 2006). A fourth key strategy is to protect, diversify, and sustainably manage the heterogeneous tree cover within the agricultural matrix. On-farm tree cover contributes to biodiversity conservation by providing additional habitats and resources for plant and animal species and enhancing landscape connectivity (Schroth et al. 2004; Harvey et al. 2005b). In addition, tree cover in pastures and fields confers benefits to farmers, providing products (fruit, wood, fodder for livestock), ameliorating microclimatic conditions, and increasing soil fertility (Nair 1989). Nevertheles, trees may also reduce agricultural productivity through competition for light, water, and nutrients and serve as hosts for pest species (Ong & Huxley 1996). A key challenge is therefore to integrate tree species in densities and spatial arrangements that minimize competition and shading of agricultural land, yet still provide biodiversity benefits. Low densities of trees scattered across the agricultural matrix and linear plantings of trees along farm and field boundaries are often compatible with existing production systems and therefore are easily adopted by farmers (Harvey et al. 2005b). A fifth strategy is to promote and conserve traditional and ecologically based agricultural practices and indigenous knowledge practices, such as agroforestry, swidden agriculture, home gardens, low-input agriculture, polycultures, and traditional milpas. These agroecological systems conserve high levels of both agrobiodiversity and wild biodiversity, ensure better soil management, and minimize agrochemical use. Throughout Mesoamerica, numerous academic, governmental, and nongovernmental organizations (e.g., CATIE, ECOSUR, EARTH, Campesino a Campesino, PROMECAFE, ACICAFOC, Sustainable Agriculture Network; Harvey et al. 2005a) already promote the use of ecological agriculture and traditional knowledge, but these efforts need to be scaled up to cover a greater proportion of the region's agricultural lands and communities. Last, agricultural land that is highly degraded, unproductive, or unsuitable (e.g., prone to erosion or colonized by exotic species) should be reforested or allowed to regenerate naturally (Montagnini 2001; Lamb et al. 2005). Restoration goals can range from restoring soil fertility for agricultural use to establishing tree plantations or forests for timber or biodiversity conservation. Reforestation efforts should include diverse mixtures of native tree species, including species that provide resources to wildlife and species that have high timber value and provide future income to local farmers. Information on many native species that could be used in large-scale restoration efforts is available (e.g., Hooper et al. 2002; Wishnie et al. 2007). Restoration can also be achieved through natural regeneration, especially where remaining tree cover provides a source of propagules. Natural regeneration can be facilitated by fencing off areas to prevent cattle entry (Guevara et al. 2004), permitting light grazing to reduce competition from grasses on tree seedlings (Posada et al. 2000), using cattle to disperse tree seeds (Miceli-Méndez et al. 2007), or retaining isolated trees or live fences that serve as nuclei for natural regeneration (Slocum 2001; Zahawi & Augspurger 2006). The use of enrichment planting in fallows can also facilitate soil restoration (Finegan & Nasi 2004). An efficient implementation of the six strategies outlined above requires that certain enabling conditions be in place at local, regional, and/or national levels. We focus here on 5 major types of programs that could facilitate our agenda: providing economic incentives, strengthening and enforcing legislation, encouraging farmer alliances, promoting sustainable agriculture certification programs, and ensuring political support (Table 2). A variety of economic instruments can be used to encourage farmers to conserve forests, retain tree cover, adopt biodiversity-friendly cropping systems, and to cover additional costs these activities may involve. Payments for environmental services (PES) hold particular promise. A Costa Rican PES scheme, in which farmers receive payments for protecting existing forest and for integrating trees into their farming systems, has worked well (Pagiola et al. 2005a; Zbinden & Lee 2005) and similar schemes are now being applied in Honduras, Guatemala, Mexico, and Nicaragua (Kosoy et al. 2007). Although PES schemes appear to be successful in conserving forest cover, they could have a greater positive impact on rural landscapes and livelihoods if they included payments for a greater diversity of sustainable land uses, removed inappropriate access restrictions (such as minimum land size), lowered transaction costs, and carefully targeted priority landscapes that have the greatest potential to conserve both biodiversity and rural livelihoods (Grieg-Gran et al. 2005; Pagiola et al. 2005b). Another economic tool with potential to reduce the conflict between conservation and farming is carbon financing for either enhancing carbon sequestration (e.g., reforestation, agroforestry, and improved agricultural land management) or reducing emissions from deforestation (Orlando et al. 2002; Moutinho & Schwartzman 2005). Reforestation activities are already eligible for funding under the Clean Development Mechanism (CDM) of the Kyoto Protocol, and the rapidly expanding voluntary markets for carbon offer new opportunities for forest restoration and conservation (Bayon et al. 2007). The complexity and high costs of CDM projects have generally small and farmer organizations from et al. 2007), but as the carbon market and demand for carbon will opportunities for farmers. such as the in Mexico, which provides smallholder farmers with access to carbon are already the et al. 1997; & 2000). In to economic incentives, our action agenda requires increasing and new that logging and agrochemical and land and conservation of forests, riparian vegetation, and tree cover et al. 2005; et al. 2005). The of Costa as a of can be achieved in the the carefully forest of and forest conversion to other land uses, logging within on on either of and the for the PES that for forest conservation and 1996). is only the first are logging for of production in and in Nicaragua et al. 2003). of and environmental by systematically forest cover, and managing is critical for forest conservation. In addition, that the establishment of conservation buffer and conservation will likely encourage natural habitat conservation on lands et al. 2000; et al. 2005). The strengthening of alliances among farmers, and conservation will also promote ecologically sustainable production systems and to approaches to biodiversity conservation and food et al. 2007; Vandermeer & Perfecto 2007). The active participation of the more than Mesoamerican farmers will be critical for long-term conservation alliances, and that promote already but these often resources to be cover only a small proportion of the region's or have than the integrated approach we are to support these types of organizations and Our action agenda could also be by efforts to small farmers with markets for agricultural and forest commodities that have been with impact on biodiversity. These biodiversity-friendly are by certification programs by of Agriculture Forest and 2003; et al. 2007). of the schemes require to with environmental such as planting trees along agrochemical and planting native vegetation along also protect farm and ensure they are working conditions, and Nevertheless, or of is often transaction costs and often and are to high levels of participation 2003; 2003). political support at all levels is needed to the strategies outlined there are positive that Mesoamerican are of the of biodiversity conservation and the need to conservation with sustainable rural Mesoamerican are of the on and have to biodiversity action that ensure protection and sustainable use of biodiversity 2005). In addition, there are many programs (e.g., and and even a for in 2005) that to some the need for reconciling biodiversity conservation and rural The have also to the Mesoamerican an to existing protected areas within and between to facilitate of plant and animal species (Miller et al. 2001). be this large-scale will require the management of the agricultural landscapes in which the protected areas are embedded and will depend on the strategies outlined in our the generally positive and promising political there is a of action on the In many the political will has not yet been into funding for implementation is and support for and is place greater attention on their for sustainable development in rural regions with resources and We for a new approach to biodiversity conservation within Mesoamerican that a focus on ecologically sustainable agriculture with existing efforts in protected areas to achieve conservation at local and levels. This new approach farmers as stakeholders in conserving biodiversity and actively farmers as to resilient landscapes that wildlife and rural livelihoods and local Our action agenda provides strategies for reconciling farming and conservation and key socioeconomic, legal, and political that could their our agenda could significant positive changes for both conservation and farming. is however. Landscapes may be degraded that conservation and restoration will be and traditional knowledge may be We therefore farmers, and other stakeholders to actively and manage landscapes to a future for both biodiversity and rural livelihoods in Mesoamerica. This by a of the on and of Landscapes of Mesoamerica by the for and by the the of and the of The working by and We are to the for the

ABSTRACT To truly understand the current status of tropical diversity and to forecast future trends, we need to increase emphasis on the study of biodiversity in rural landscapes that are actively managed or modified by people. We present an integrated landscape approach to promote research in human‐modified landscapes that includes the effects of landscape structure and dynamics on conservation of biodiversity, provision of ecosystem services, and sustainability of rural livelihoods. We propose research priorities encompassing three major areas: biodiversity, human–environment interactions, and restoration ecology. We highlight key areas where we lack knowledge and where additional understanding is most urgent for promoting conservation and sustaining rural livelihoods. Finally, we recommend participatory and multidisciplinary approaches in research and management. Lasting conservation efforts demand new alliances among conservation biologists, agroecologists, agronomists, farmers, indigenous peoples, rural social movements, foresters, social scientists, and land managers to collaborate in research, co‐design conservation programs and policies, and manage human‐modified landscapes in ways that enhance biodiversity conservation and promote sustainable livelihoods.

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.

The coffee berry borer (Hypothenemus hampei) is the most devastating insect pest of coffee worldwide with its infestations decreasing crop yield by up to 80%. Caffeine is an alkaloid that can be toxic to insects and is hypothesized to act as a defence mechanism to inhibit herbivory. Here we show that caffeine is degraded in the gut of H. hampei, and that experimental inactivation of the gut microbiota eliminates this activity. We demonstrate that gut microbiota in H. hampei specimens from seven major coffee-producing countries and laboratory-reared colonies share a core of microorganisms. Globally ubiquitous members of the gut microbiota, including prominent Pseudomonas species, subsist on caffeine as a sole source of carbon and nitrogen. Pseudomonas caffeine demethylase genes are expressed in vivo in the gut of H. hampei, and re-inoculation of antibiotic-treated insects with an isolated Pseudomonas strain reinstates caffeine-degradation ability confirming their key role.

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.

Tropical forests disappear rapidly because of deforestation, yet they have the potential to regrow naturally on abandoned lands. We analyze how 12 forest attributes recover during secondary succession and how their recovery is interrelated using 77 sites across the tropics. Tropical forests are highly resilient to low-intensity land use; after 20 years, forest attributes attain 78% (33 to 100%) of their old-growth values. Recovery to 90% of old-growth values is fastest for soil (<1 decade) and plant functioning (<2.5 decades), intermediate for structure and species diversity (2.5 to 6 decades), and slowest for biomass and species composition (>12 decades). Network analysis shows three independent clusters of attribute recovery, related to structure, species diversity, and species composition. Secondary forests should be embraced as a low-cost, natural solution for ecosystem restoration, climate change mitigation, and biodiversity conservation.

Low-density polyethylene (LDPE) is the most abundant source of microplastic pollution worldwide. A recent study found that LDPE decay was increased and the size of the plastic was decreased after passing through the gut of the earthworm Lumbricus terrestris (Oligochaeta). Here, we investigated the involvement of earthworm gut bacteria in the microplastic decay. The bacteria isolated from the earthworm's gut were Gram-positive, belonging to phylum Actinobacteria and Firmicutes. These bacteria were used in a short-term microcosm experiment performed with gamma-sterilized soil with or without LDPE microplastics (MP). We observed that the LDPE-MP particle size was significantly reduced in the presence of bacteria. In addition, the volatile profiles of the treatments were compared and clear differences were detected. Several volatile compounds such as octadecane, eicosane, docosane and tricosane were measured only in the treatments containing both bacteria and LDPE-MP, indicating that these long-chain alkanes are byproducts of bacterial LDPE-MP decay.

Studies have documented biodiversity losses due to intensification of coffee management (reduction in canopy richness and complexity). Nevertheless, questions remain regarding relative sensitivity of different taxa, habitat specialists, and functional groups, and whether implications for biodiversity conservation vary across regions.We quantitatively reviewed data from ant, bird, and tree biodiversity studies in coffee agroecosystems to address the following questions: Does species richness decline with intensification or with individual vegetation characteristics? Are there significant losses of species richness in coffee-management systems compared with forests? Is species loss greater for forest species or for particular functional groups?and Are ants or birds more strongly affected by intensification? Across studies, ant and bird richness declined with management intensification and with changes in vegetation. Species richness of all ants and birds and of forest ant and bird species was lower in most coffee agroecosystems than in forests, but rustic coffee (grown under native forest canopies) had equal or greater ant and bird richness than nearby forests. Sun coffee(grown without canopy trees) sustained the highest species losses, and species loss of forest ant, bird, and tree species increased with management intensity. Losses of ant and bird species were similar, although losses of forest ants were more drastic in rustic coffee. Richness of migratory birds and of birds that forage across vegetation strata was less affected by intensification than richness of resident, canopy, and understory bird species. Rustic farms protected more species than other coffee systems, and loss of species depended greatly on habitat specialization and functional traits. We recommend that forest be protected, rustic coffee be promoted,and intensive coffee farms be restored by augmenting native tree density and richness and allowing growth of epiphytes. We also recommend that future research focus on potential trade-offs between biodiversity conservation and farmer livelihoods stemming from coffee production.

Agroecology as a transformative movement has gained momentum in many countries worldwide. In several cases, the implementation of agroecological practices has grown beyond isolated, local experiences to be employed by ever-greater numbers of families and communities over ever-larger territories and to engage more people in the processing, distribution, and consumption of agroecologically produced food. To understand the nonlinear, multidimensional processes that have enabled and impelled the bringing to scale of agroecology, we review and analyze emblematic cases that include the farmer-to-farmer movement in Central America; the national peasant agroecology movement in Cuba; the organic coffee boom in Chiapas, Mexico; the spread of Zero Budget Natural Farming in Karnataka, India; and the agroecological farmer–consumer marketing network “Rede Ecovida,” in Brazil. On the basis of our analysis, we identify eight key drivers of the process of taking agroecology to scale: (1) recognition of a crisis that motivates the search for alternatives, (2) social organization, (3) constructivist learning processes, (4) effective agroecological practices, (5) mobilizing discourses, (6) external allies, (7) favorable markets, and (8) favorable policies. This initial analysis shows that organization and social fabric are the growth media on which agroecology advances, with the help of the other drivers. A more detailed understanding is needed on how these multiple dimensions interact with, reinforce, and generate positive feedback with each other to make agroecology’s territorial expansion possible.