Agroforestry enhances biological activity, diversity and soil-based ecosystem functions in mountain agroecosystems of Latin America: A meta-analysis.

Mountain agroecosystems in Latin America provide multiple ecosystem functions (EFs) and products from global to local scales, particularly for the rural communities who depend on them. Agroforestry has been proposed as a climate-smart farming strategy throughout much of the region to help conserve biodiversity and enhance multiple EFs, especially in mountainous regions. However, large-scale synthesis on the potential of agroforestry across Latin America is lacking. To understand the potential impacts of agroforestry at the continental level, we conducted a meta-analysis examining the effects of agroforestry on biological activity and diversity (BIAD) and multiple EFs across mountain agroecosystems of Latin America. A total of 78 studies were selected based on a formalized literature search in the Web of Science. We analysed differences between (i) silvoarable systems versus cropland, (ii) silvopastoral systems versus pastureland, and (iii) agroforestry versus forest systems, based on response ratios. Response ratios were further used to understand how climate type, precipitation and soil properties (texture) influence key EFs (carbon sequestration, nutrient provision, erosion control, yield production) and BIAD in agroforestry systems. Results revealed that BIAD and EFs related to carbon sequestration and nutrient provisioning were generally higher in agroforestry systems (silvopastoral and silvoarable) compared to croplands and pasturelands without trees. However, the impacts of agroforestry systems on crop yields varied depending on the system considered (i.e., coffee vs. cereals), while forest systems generally provided greater levels of BIAD and EFs than agroforestry systems. Further analysis demonstrated that the impacts of agroforestry systems on BIAD and EFs depend greatly on climate type, soil, and precipitation. For example, silvoarable systems appear to generate the greatest benefits in arid or tropical climates, on sandier soils, and under lower precipitation regimes. Overall, our findings highlight the widespread potential of agroforestry systems to BIAD and multiple EFs across montane regions of Latin America.

The biodiversity and ecosystem service contributions and trade-offs of forest restoration approaches.

Forest restoration is being scaled up globally to deliver critical ecosystem services and biodiversity benefits; however, there is a lack of rigorous comparison of cobenefit delivery across different restoration approaches. Through global synthesis, we used 25,950 matched data pairs from 264 studies in 53 countries to assess how delivery of climate, soil, water, and wood production services, in addition to biodiversity, compares across a range of tree plantations and native forests. Benefits of aboveground carbon storage, water provisioning, and especially soil erosion control and biodiversity are better delivered by native forests, with compositionally simpler, younger plantations in drier regions performing particularly poorly. However, plantations exhibit an advantage in wood production. These results underscore important trade-offs among environmental and production goals that policy-makers must navigate in meeting forest restoration commitments.

Biodiversity responses to restoration across the Brazilian Atlantic Forest.

The UN Decade on Ecosystem Restoration is focussing attention and resources on restoration globally. Nowhere is this more crucial than in tropical forests that harbor immense biodiversity, but have also undergone widespread deforestation over the past few decades. We performed a meta-analysis to investigate how biodiversity features respond to forest restoration across the Brazilian Atlantic Forest (BAF), one of the most threatened biodiversity hotspots in the world. We assembled biodiversity in different metrics of structure and diversity features of three taxonomic groups (vascular plants, soil microorganisms, and invertebrates), generating a dataset with 2370 observations from 76 primary studies. We quantified the incomplete recovery of biodiversity (i.e., the rate of recovery to a pre-disturbance state) occurring during the restoration process, which we called the 'recovery gap'. Our results revealed that forests undergoing restoration in the BAF show a recovery gap of 34% for structure features and 22% for diversity features in comparison to reference reforests, considering all taxonomic groups investigated. For vascular plants, soil microorganisms, and invertebrates the recovery gap ranged between 46 and 47%, 16-26%, and 4-7%, respectively. Overall, the recovery gap was influenced by the interaction of restoration actions (i.e., the past land use, restoration age and restoration approach - active and passive restoration), however, structure features responded more sensitively to the time elapsed since restoration started, while the recovery gap for diversity features depended more on the past land-use. Our study can help guide the prioritization of the aforenamed taxonomic groups in restoration, the regulation of potential biodiversity offsetting policies in the BAF, and understanding how coupled biodiversity features respond to the interaction of environmental conditions and restoration actions in a high fragmented tropical landscape.

Reliability of evidence-review methods in restoration ecology.

In restoration science, evidence reviews play a crucial role in summarizing research findings in practice and policy. However, if unreliable or inappropriate methods are used to review evidence, decisions based on these reviews may not accurately reflect the available evidence base. To assess the current value of restoration reviews, we examined a sample of meta-analyses and narrative syntheses (n = 91) with the Collaboration for Environmental Evidence Synthesis Assessment Tool (CEESAT), which uses detailed criteria to assesses the method of policy-relevant evidence synthesis according to elements important for objectivity, transparency, and comprehensiveness. Overall, reviews scored low based on this standard: median score 16 out of 39, modal score 15, and mean 16.6. Meta-analyses scored higher than narrative syntheses (median 17 vs. 5, respectively), although there were some outlier narrative syntheses that had high scores, suggesting that quantitative synthesis does not solely reflect the reliability of a review. In general, criteria spanning the more fundamental review stages (i.e., searching for studies and including studies) received low scores for both synthesis types. Conversely, criteria comprising the later stages of the review (i.e., critical appraisal, data extraction, and data synthesis) were generally well described in meta-analyses; thus, these criteria achieved the highest individual CEESAT scores. We argue that restoration ecology is well positioned to advance so-called evidence-based restoration, but review authors should elucidate their conceptual understanding of evidence syntheses and recognize that conducting reliable reviews demands the same methodological rigor and reporting standards used in primary research. Given the potential of evidence reviews to inform management, policy, and research, it is of vital importance that the overall methodological reliability of restoration reviews be improved.

Confiabilidad de los Métodos de Revisión de Evidencias en la Ecología de Restauración Resumen Para las ciencias de la restauración, las revisiones de evidencias juegan un papel muy importante en la síntesis de los hallazgos de las investigaciones en la práctica y en las políticas. Sin embargo, si se usan métodos poco fiables o inapropiados para revisar las evidencias, las decisiones que se tomen con base en estas revisiones pueden no reflejar acertadamente la base disponible de evidencias. Para analizar el valor actual de las revisiones de restauraciones examinamos una muestra de metaanálisis y síntesis narrativas (n = 91) con la Herramienta para la Síntesis de Análisis de la Colaboración para la Evidencia Ambiental (CEESAT), la cual usa criterios detallados para analizar el método de síntesis de evidencias relevantes para las políticas de acuerdo con los elementos importantes para la objetividad, transparencia y exhaustividad. En general, las revisiones tuvieron puntajes bajos con base en este estándar (puntaje medio: 16 de 39, puntaje modal: 15, media: 16.6). Los metaanálisis tuvieron un puntaje más alto que las síntesis narrativas (mediana: 17 vs 5, respectivamente), aunque hubo algunas síntesis narrativas atípicas que tuvieron puntajes altos, lo que sugiere que la síntesis cuantitativa no refleja por sí sola la confiabilidad de una revisión. En suma, los criterios que abarcaron las etapas de revisión más fundamentales (es decir, buscar estudios e incluir estudios) recibieron puntajes bajos para ambos tipos de síntesis. Al contrario, los criterios que comprendieron las etapas tardías de la revisión (es decir, la valoración crítica, la extracción de datos y la síntesis de los datos) estuvieron generalmente bien descritos en los metaanálisis; por lo tanto, estos criterios alcanzaron los puntajes CEESAT individuales más altos. Argumentamos que la ecología de restauración se encuentra bien posicionada para adelantar la llamada restauración basada en evidencias, pero los autores de las revisiones deberían aclarar su entendimiento conceptual de la síntesis de evidencias y reconocer que la realización de revisiones confiables requiere el mismo rigor metodológico y los mismos estándares de reporte usados en la investigación primaria. Dado el potencial que tienen las revisiones de evidencias para orientar el manejo, las políticas y la investigación, es de vital importancia que se mejore la confiabilidad metodológica generalizada de las revisiones de restauración.

Meta-analysis of heavy metal effects on soil enzyme activities.

Enzyme activities (EAs) respond to contamination in several ways depending on the chemical form and content of heavy metals and metalloids (HMs) and their interactions with various soil properties. A systematic and mechanistic understanding of EA responses to HM contamination in soil is necessary for predicting the consequences for nutrient availability and the cycling of carbon (C), nitrogen (N), phosphorus (P) and sulphur (S). In this study, a meta-analysis based on 671 observations found the activities of seven enzymes to decrease in response to soil contamination with Pb, Zn, Cd, Cu and As. HM contamination linearly reduced the activities of all enzymes in the following order: arylsulfatase > dehydrogenase > ß-glucosidase > urease > acid phosphatase > alkaline phosphatase > catalase. The activities of two endoenzymes: arylsulfatase (partly as exoenzyme) and dehydrogenase were reduced by 72% and 64%, respectively. These reductions were two times greater than of exoenzymes: ß-glucosidase, urease, acid phosphatase, alkaline phosphatase and catalase (partly endoenzyme). This reflects the much stronger impact of HMs on living microorganisms and their endoenzymes than on extracellular enzymes stabilized on clay minerals and organic matter. Increasing clay content weakened the negative effects of HM contamination on EAs. All negative effects of HMs on EAs decreased with soil depth because HMs remain mainly in the topsoil. EAs involved in the cycling of C and S were more affected by HMs than the enzymes associated with the cycling of N and P. Consequently, HM contamination may alter the stoichiometry of C, N, P and S released by enzymatic decomposition of organic compounds that consequently affect microbial community structure and activity.

Restoration and repair of Earth's damaged ecosystems.

Given that few ecosystems on the Earth have been unaffected by humans, restoring them holds great promise for stemming the biodiversity crisis and ensuring ecosystem services are provided to humanity. Nonetheless, few studies have documented the recovery of ecosystems globally or the rates at which ecosystems recover. Even fewer have addressed the added benefit of actively restoring ecosystems versus allowing them to recover without human intervention following the cessation of a disturbance. Our meta-analysis of 400 studies worldwide that document recovery from large-scale disturbances, such as oil spills, agriculture and logging, suggests that though ecosystems are progressing towards recovery following disturbances, they rarely recover completely. This result reinforces conservation of intact ecosystems as a key strategy for protecting biodiversity. Recovery rates slowed down with time since the disturbance ended, suggesting that the final stages of recovery are the most challenging to achieve. Active restoration did not result in faster or more complete recovery than simply ending the disturbances ecosystems face. Our results on the added benefit of restoration must be interpreted cautiously, because few studies directly compared different restoration actions in the same location after the same disturbance. The lack of consistent value added of active restoration following disturbance suggests that passive recovery should be considered as a first option; if recovery is slow, then active restoration actions should be better tailored to overcome specific obstacles to recovery and achieve restoration goals. We call for a more strategic investment of limited restoration resources into innovative collaborative efforts between scientists, local communities and practitioners to develop restoration techniques that are ecologically, economically and socially viable.

A global review of past land use, climate, and active vs. passive restoration effects on forest recovery.

Global forest restoration targets have been set, yet policy makers and land managers lack guiding principles on how to invest limited resources to achieve them. We conducted a meta-analysis of 166 studies in naturally regenerating and actively restored forests worldwide to answer: (1) To what extent do floral and faunal abundance and diversity and biogeochemical functions recover? (2) Does recovery vary as a function of past land use, time since restoration, forest region, or precipitation? (3) Does active restoration result in more complete or faster recovery than passive restoration? Overall, forests showed a high level of recovery, but the time to recovery depended on the metric type measured, past land use, and region. Abundance recovered quickly and completely, whereas diversity recovered slower in tropical than in temperate forests. Biogeochemical functions recovered more slowly after agriculture than after logging or mining. Formerly logged sites were mostly passively restored and generally recovered quickly. Mined sites were nearly always actively restored using a combination of planting and either soil amendments or recontouring topography, which resulted in rapid recovery of the metrics evaluated. Actively restoring former agricultural land, primarily by planting trees, did not result in consistently faster or more complete recovery than passively restored sites. Our results suggest that simply ending the land use is sufficient for forests to recover in many cases, but more studies are needed that directly compare the value added of active versus passive restoration strategies in the same system. Investments in active restoration should be evaluated relative to the past land use, the natural resilience of the system, and the specific objectives of each project.

Anthropogenic ecosystem disturbance and the recovery debt.

Ecosystem recovery from anthropogenic disturbances, either without human intervention or assisted by ecological restoration, is increasingly occurring worldwide. As ecosystems progress through recovery, it is important to estimate any resulting deficit in biodiversity and functions. Here we use data from 3,035 sampling plots worldwide, to quantify the interim reduction of biodiversity and functions occurring during the recovery process (that is, the 'recovery debt'). Compared with reference levels, recovering ecosystems run annual deficits of 46-51% for organism abundance, 27-33% for species diversity, 32-42% for carbon cycling and 31-41% for nitrogen cycling. Our results are consistent across biomes but not across degrading factors. Our results suggest that recovering and restored ecosystems have less abundance, diversity and cycling of carbon and nitrogen than 'undisturbed' ecosystems, and that even if complete recovery is reached, an interim recovery debt will accumulate. Under such circumstances, increasing the quantity of less-functional ecosystems through ecological restoration and offsetting are inadequate alternatives to ecosystem protection.

Restoration enhances wetland biodiversity and ecosystem service supply, but results are context-dependent: a meta-analysis.

Wetlands are valuable ecosystems because they harbor a huge biodiversity and provide key services to societies. When natural or human factors degrade wetlands, ecological restoration is often carried out to recover biodiversity and ecosystem services (ES). Although such restorations are routinely performed, we lack systematic, evidence-based assessments of their effectiveness on the recovery of biodiversity and ES. Here we performed a meta-analysis of 70 experimental studies in order to assess the effectiveness of ecological restoration and identify what factors affect it. We compared selected ecosystem performance variables between degraded and restored wetlands and between restored and natural wetlands using response ratios and random-effects categorical modeling. We assessed how context factors such as ecosystem type, main agent of degradation, restoration action, experimental design, and restoration age influenced post-restoration biodiversity and ES. Biodiversity showed excellent recovery, though the precise recovery depended strongly on the type of organisms involved. Restored wetlands showed 36% higher levels of provisioning, regulating and supporting ES than did degraded wetlands. In fact, wetlands showed levels of provisioning and cultural ES similar to those of natural wetlands; however, their levels of supporting and regulating ES were, respectively, 16% and 22% lower than in natural wetlands. Recovery of biodiversity and of ES were positively correlated, indicating a win-win restoration outcome. The extent to which restoration increased biodiversity and ES in degraded wetlands depended primarily on the main agent of degradation, restoration actions, experimental design, and ecosystem type. In contrast, the choice of specific restoration actions alone explained most differences between restored and natural wetlands. These results highlight the importance of comprehensive, multi-factorial assessment to determine the ecological status of degraded, restored and natural wetlands and thereby evaluate the effectiveness of ecological restorations. Future research on wetland restoration should also seek to identify which restoration actions work best for specific habitats.

Environmental analysis in the selection of alternative corridors in a long-distance linear project: a methodological proposal.

A linear engineering project--i.e. a pipeline--has a potential long- and short-term impact on the environment and on the inhabitants therein. We must find better, less expensive, and less time-consuming ways to obtain information on the environment and on any modifications resulting from anthropic activity. We need scientifically sound, rapid and affordable assessment and monitoring methods. Construction companies, industries and the regulating government organisms lack the resources needed to conduct long-term basic studies of the environment. Thus there is a need to make the necessary adjustments and improvements in the environmental data considered useful for this development project. More effective and less costly methods are generally needed. We characterized the landscape of the study area, situated in the center and north-east of Argentina. Little is known of the ecology of this region and substantial research is required in order to develop sustainable uses and, at the same time, to develop methods for reducing impacts, both primary and secondary, resulting from anthropic activity in this area. Furthermore, we made an assessment of the environmental impact of the planned linear project, applying an ad hoc impact index, and we analyzed the different alternatives for a corridor, each one of these involving different sections of the territory. Among the alternative corridors considered, this study locates the most suitable ones in accordance with a selection criterion based on different environmental and conservation aspects. We selected the corridor that we considered to be the most compatible--i.e. with the least potential environmental impact--for the possible construction and operation of the linear project. This information, along with suitable measures for mitigating possible impacts, should be the basis of an environmental management plan for the design process and location of the project. We pointed out the objectivity and efficiency of this methodological approach, along with the possibility of integrating the information in order to allow for the application thereof in this type of study.

Restauración ecológica de bosques tropicales: veinte años de investigación académica / Tropical forest restoration: twenty years of academic research

La restauración ecológica es una disciplina de origen reciente, que se enfoca hacia la rehabilitación biótica y abiótica de los sistemas naturales, con la idea de restituir su estrucatura y procesos funcionales. El estudio de la restauración de bosques tropicales se ha concentrado en la identificación de los factores que limitan la regeneración, cuyo manejo permitirá controlar y acelerar la sucesión secundaria. Entre estos se incluyen: la carencia de dispersión o de propágulos en el banco de semillas, bajas tasas de germinación, bajas tasas de reclutamiento debido a los efectos negativos de las enfermedades, depredación y competencia, o a condiciones físicas adversas. Con base en el análisis de la literatura de 20 años de investigación en la restauración de los bosques tropicales, en este trabajo se evalúa el escenario actual y las perspectivas de esta disciplina. Se observa que 64 por ciento de los estudios se realizan en la selva húmeda que 55 por ciento de ellos son fundamentalemente descriptivos y que en los estudios experimentales existe la tendencia a abordar uno o dos factores limitantes, en lugar de tener una visión integral y a largo plazo. Sin embargo, la situación resulta prometedora; Los trabajos experimentales han crecido exponencialmente desde su inicio y es incipiente de la inclusión del componente social en los proyectos. La restauración ecológica está en camino a consolidarse como uan disciplina integradora, que incluya los aspectos ecológico, social, y económico, para lograr la recuperación y conservación de los sistemas naturales