Response of the endangered tropical dry forests to climate change and the role of Mexican Protected Areas for their conservation

Assuming that co‐distributed species are exposed to similar environmental conditions, ecological niche models (ENMs) of bird and plant species inhabiting tropical dry forests (TDFs) in Mexico were developed to evaluate future projections of their distribution for the years 2050 and 2070. We used ENM‐based predictions and climatic data for two Global Climate Models, considering two Representative Concentration Pathway scenarios (RCP4.5/RCP8.5). We also evaluated the effects of habitat loss and the importance of the Mexican system of protected areas (PAs) on the projected models for a more detailed prediction of TDFs and to identify hot spots that require conservation actions. We identified four major distributional areas: the main one located along the Pacific Coast (from Sonora to Chiapas, including the Cape and Bajío regions, and the Balsas river basin), and three isolated areas: the Yucatán peninsula, central Veracruz, and southern Tamaulipas. When considering the effect of habitat loss, a significant reduction (~61%) of the TDFs predicted area occurred, whereas climate‐change models suggested (in comparison with the present distribution model) an increase in area of 3.0–10.0% and 3.0–9.0% for 2050 and 2070, respectively. In future scenarios, TDFs will occupy areas above its current average elevational distribution that are outside of its present geographical range. Our findings show that TDFs may persist in Mexican territory until the middle of the XXI century; however, the challenges about long‐term conservation are partially addressed (only 7% unaffected within the Mexican network of PAs) with the current Mexican PAs network. Based on our ENM approach, we suggest that a combination of models of species inhabiting present TDFs and taking into account change scenarios represent an invaluable tool to create new PAs and ecological corridors, as a response to the increasing levels of habitat destruction and the effects of climate change on this ecosystem.     

Implications of climate change on the habitat shifts of tropical lizards

The effect of temperature on the distributions of ectothermic vertebrates is well documented. Despite the increase of 6°C expected in the next 60 years in South America, numerous vertebrates are still considered as ‘Least Concern’ species by the IUCN due to their large distribution, insufficient widespread threats and insignificant population decline. One example is the lizard Tropidurus torquatus (Squamata: Tropiduridae), commonly found thermoregulating in anthropic environments throughout the Brazilian Cerrado, but restricted to gallery forests in the equator‐ward localities. The urban areas in this warmer region have been colonised by other closely related congeners (e.g. Tropidurus oreadicus). This study aimed to understand this divergence of habitat selection by these tropirudids that may explain some of the species responses to past and future climate warming. We collected body temperatures (T_b), micro‐environmental temperatures (T_a) and operative (T_e) temperatures in four sites along a latitudinal gradient: a pole‐ward and two central sites where T. torquatus inhabit urban areas and one equator‐ward site where T. torquatus and T. oreadicus occur in the gallery forest and in urban microhabitats, respectively. All three populations of T. torquatus present similar T_b (35.5–36°C) and shared microhabitats with a similar T_a (34–37.3°C). The T_e in the equator‐ward urban site was considerably higher than in the gallery forest. Tropidurus oreadicus T_b was 38.2 °C (30.1–41.3°C) and was active at a T_a of 30.5–42.3°C. The overlap between the genus T_b, T_a and T_e highlights a decrease in the hours of activity that lizards would experience under climate warming. The reduction of hours of activity together with the devastation of natural habitats represents threats and an alarming scenario especially for the equator‐ward populations.     

Impacts of climate variability on tree demography in second growth tropical forests: the importance of regional context for predicting successional trajectories

Naturally regenerating and restored second growth forests account for over 70% of tropical forest cover and provide key ecosystem services. Understanding climate change impacts on successional trajectories of these ecosystems is critical for developing effective large‐scale forest landscape restoration (FLR) programs. Differences in environmental conditions, species composition, dynamics, and landscape context from old growth forests may exacerbate climate impacts on second growth stands. We compile data from 112 studies on the effects of natural climate variability, including warming, droughts, fires, and cyclonic storms, on demography and dynamics of second growth forest trees and identify variation in forest responses across biomes, regions, and landscapes. Across studies, drought decreases tree growth, survival, and recruitment, particularly during early succession, but the effects of temperature remain unexplored. Shifts in the frequency and severity of disturbance alter successional trajectories and increase the extent of second growth forests. Vulnerability to climate extremes is generally inversely related to long‐term exposure, which varies with historical climate and biogeography. The majority of studies, however, have been conducted in the Neotropics hindering generalization. Effects of fire and cyclonic storms often lead to positive feedbacks, increasing vulnerability to climate extremes and subsequent disturbance. Fragmentation increases forests’ vulnerability to fires, wind, and drought, while land use and other human activities influence the frequency and intensity of fire, potentially retarding succession. Comparative studies of climate effects on tropical forest succession across biogeographic regions are required to forecast the response of tropical forest landscapes to future climates and to implement effective FLR policies and programs in these landscapes.     

Estimating aboveground net biomass change for tropical and subtropical forests: Refinement of IPCC default rates using forest plot data

As countries advance in greenhouse gas (GHG) accounting for climate change mitigation, consistent estimates of aboveground net biomass change (?AGB) are needed. Countries with limited forest monitoring capabilities in the tropics and subtropics rely on IPCC 2006 default ?AGB rates, which are values per ecological zone, per continent. Similarly, research into forest biomass change at a large scale also makes use of these rates. IPCC 2006 default rates come from a handful of studies, provide no uncertainty indications and do not distinguish between older secondary forests and old‐growth forests. As part of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, we incorporate ?AGB data available from 2006 onwards, comprising 176 chronosequences in secondary forests and 536 permanent plots in old‐growth and managed/logged forests located in 42 countries in Africa, North and South America and Asia. We generated ?AGB rate estimates for younger secondary forests (≤20 years), older secondary forests (>20 years and up to 100 years) and old‐growth forests, and accounted for uncertainties in our estimates. In tropical rainforests, for which data availability was the highest, our ?AGB rate estimates ranged from 3.4 (Asia) to 7.6 (Africa) Mg ha^?1 year^?1 in younger secondary forests, from 2.3 (North and South America) to 3.5 (Africa) Mg ha^?1 year^?1 in older secondary forests, and 0.7 (Asia) to 1.3 (Africa) Mg ha^?1 year^?1 in old‐growth forests. We provide a rigorous and traceable refinement of the IPCC 2006 default rates in tropical and subtropical ecological zones, and identify which areas require more research on ?AGB. In this respect, this study should be considered as an important step towards quantifying the role of tropical and subtropical forests as carbon sinks with higher accuracy; our new rates can be used for large‐scale GHG accounting by governmental bodies, nongovernmental organizations and in scientific research.     

The impact of global climate change on tropical forest biodiversity in Amazonia

Aim To model long‐term trends in plant species distributions in response to predicted changes in global climate. Location Amazonia. Methods The impacts of expected global climate change on the potential and realized distributions of a representative sample of 69 individual Angiosperm species in Amazonia were simulated from 1990 to 2095. The climate trend followed the HADCM2GSa1 scenario, which assumes an annual 1% increase of atmospheric CO₂ content with effects mitigated by sulphate forcing. Potential distributions of species in one‐degree grid cells were modelled using a suitability index and rectilinear envelope based on bioclimate variables. Realized distributions were additionally limited by spatial contiguity with, and proximity to, known record sites. A size‐structured population model was simulated for each cell in the realized distributions to allow for lags in response to climate change, but dispersal was not included. Results In the resulting simulations, 43% of all species became non‐viable by 2095 because their potential distributions had changed drastically, but there was little change in the realized distributions of most species, owing to delays in population responses. Widely distributed species with high tolerance to environmental variation exhibited the least response to climate change, and species with narrow ranges and short generation times the greatest. Climate changed most in north‐east Amazonia while the best remaining conditions for lowland moist forest species were in western Amazonia. Main conclusions To maintain the greatest resilience of Amazonian biodiversity to climate change as modelled by HADCM2GSa1, highest priority should be given to strengthening and extending protected areas in western Amazonia that encompass lowland and montane forests.     

Leaf litter inhabiting beetles as surrogates for establishing priorities for conservation of selected tropical montane cloud forests in Honduras, Central America (Coleoptera; Staphylinidae, Curculionidae)

Thirteen tropical montane cloud forests (TMCFs) in Honduras and adjacent El Salvador were evaluated for species diversity and endemism in leaf litter inhabiting Curculionidae (weevils) and Staphylinidae in June and August of 1994. Totals of 26,891 specimens representing 293 species of Curculionidae, and 7349 specimens representing 224 species of Staphylinidae, were collected. Regional endemism was high with 173 species (58.7% of total) of Curculionidae and 126 species (56.3% of total) of Staphylinidae, restricted to single sites. Measures of diversity (number of observed species [Sobs]; number of endemic species) and estimates of biodiversity (Chao 2, first and second order Jackknife and Bootstrap richness estimators) are given for each site for Curculionidae and Staphylinidae. Priority-areas analyses based on Sobs (Greedy), Sobs, Chao 2, number of endemic species, site complementarity and higher taxonomic diversity (Curculionidae only) are presented. Weak or lack of correlation was noted between site area and site diversity for either Curculionidae or Staphylinidae. The optimum sequence for site conservation was determined based on Sobs (Greedy). Four sites are identified as the highest conservation priorities; Parque Nacional Montecristo, P.N. La Muralla, P.N. Santa Barbara and P.N. Comayagua. Identification as high priority sites supports their designation as Parques Nacionales rather than the less diverse Reservas Biologias or Reservas Vidas Silvestres. While closely approximating performance of Sobs (Greedy), no one of Sobs, number of endemics, Chao 2 or site complementarity give results equivalent to the optimum sequence based on Sobs (Greedy) and the latter is concluded to be the best method for establishing conservation priorities in TMCF. Results of the analyses based on one of Curculionidae or Staphylinidae differ in the ordering of site priorities based on each of Sobs, Chao 2 or number of endemics at each site, with at best, weak positive correlations between results based on each taxon. Data from other taxa are necessary to determine if one of Curculionidae or Staphylinidae emerges as the better surrogate for general patterns of biodiversity in TMCF. Conservation strategies in Central America should emphasize the importance of TMCF particularly in view of high regional endemism. In formulating these strategies, consideration needs to be given to the preservation of many small regional preserves rather than fewer larger preserves. Data from inventories of other taxa should be included where available and all biological data should be integrated with social and cultural issues of regional importance.     

Trait‐based approaches to analyze links between the drivers of change and ecosystem services: Synthesizing existing evidence and future challenges

Understanding the responses of biodiversity to drivers of change and the effects of biodiversity on ecosystem properties and ecosystem services is a key challenge in the context of global environmental change. We performed a systematic review and meta‐analysis of the scientific literature linking direct drivers of change and ecosystem services via functional traits of three taxonomic groups (vegetation, invertebrates, and vertebrates) to: (1) uncover trends and research biases in this field; and (2) synthesize existing empirical evidence. Our results show the existence of important biases in published studies related to ecosystem types, taxonomic groups, direct drivers of change, ecosystem services, geographical range, and the spatial scale of analysis. We found multiple evidence of links between drivers and services mediated by functional traits, particularly between land‐use changes and regulating services in vegetation and invertebrates. Seventy‐five functional traits were recorded in our sample. However, few of these functional traits were repeatedly found to be associated with both the species responses to direct drivers of change (response traits) and the species effects on the provision of ecosystem services (effect traits). Our results highlight the existence of potential “key functional traits,” understood as those that have the capacity to influence the provision of multiple ecosystem services, while responding to specific drivers of change, across a variety of systems and organisms. Identifying “key functional traits” would help to develop robust indicator systems to monitor changes in biodiversity and their effects on ecosystem functioning and ecosystem services supply.     

A decade of climate change experiments on marine organisms: procedures,patterns and problems

The first decade of the new millennium saw a flurry of experiments to establish a mechanistic understanding of how climate change might transform the global biota, including marine organisms. However, the biophysical properties of the marine environment impose challenges to experiments, which can weaken their inference space. To facilitate strengthening the experimental evidence for possible ecological consequences of climate change, we reviewed the physical, biological and procedural scope of 110 marine climate change experiments published between 2000 and 2009. We found that 65% of these experiments only tested a single climate change factor (warming or acidification), 54% targeted temperate organisms, 58% were restricted to a single species and 73% to benthic invertebrates. In addition, 49% of the reviewed experiments had issues with the experimental design, principally related to replication of the main test‐factors (temperature or pH), and only 11% included field assessments of processes or associated patterns. Guiding future research by this inventory of current strengths and weaknesses will expand the overall inference space of marine climate change experiments. Specifically, increased effort is required in five areas: (i) the combined effects of concurrent climate and non‐climate stressors; (ii) responses of a broader range of species, particularly from tropical and polar regions as well as primary producers, pelagic invertebrates, and fish; (iii) species interactions and responses of species assemblages, (iv) reducing pseudo‐replication in controlled experiments; and (v) increasing realism in experiments through broad‐scale observations and field experiments. Attention in these areas will improve the generality and accuracy of our understanding of climate change as a driver of biological change in marine ecosystems.     

Extinction vulnerability of tropical montane endemism from warming and upslope displacement: a preliminary appraisal for the highest massif in Madagascar

One of the predicted biological responses to climate warming is the upslope displacement of species distributions. In the tropics, because montane assemblages frequently include local endemics that are distributed close to summits, these species may be especially vulnerable to experiencing complete habitat loss from warming. However, there is currently a dearth of information available for tropical regions. Here, we present a preliminary appraisal of this extinction threat using the herpetological assemblage of the Tsaratanana Massif in northern Madagascar (the island's highest massif), which is rich with montane endemism. We present meteorological evidence (individual and combined regional weather station data and reanalysis forecast data) for recent warming in Madagascar, and show that this trend is consistent with recent climate model simulations. Using standard moist adiabatic lapse rates, these observed meteorological warming trends in northern Madagascar predict upslope species displacement of 17–74 m per decade between 1993 and 2003. Over this same period, we also report preliminary data supporting a trend for upslope distribution movements, based on two surveys we completed at Tsaratanana. For 30 species, representing five families of reptiles and amphibians, we found overall mean shifts in elevational midpoint of 19–51 m upslope (mean lower elevation limit 29–114 m; mean upper elevation limit ?8 to 53 m). We also found upslope trends in mean and median elevational observations in seven and six of nine species analysed. Phenological differences between these surveys do not appear to be substantial, but these upslope shifts are consistent with the predictions based on meteorological warming. An elevational range displacement analysis projects complete habitat loss for three species below the 2 °C ‘dangerous’ warming threshold. One of these species is not contracting its distribution, but the other two were not resampled in 2003. A preliminary review of the other massifs in Madagascar indicates potential similar vulnerability to habitat loss and upslope extinction. Consequently, we urgently recommend additional elevational surveys for these and other tropical montane assemblages, which should also include, when possible, the monitoring of local meteorological conditions and habitat change.     

Impacts of hunting on mammals in African tropical moist forests: a review and synthesis

• 1 Available information on the consumption of wild meat in West and Central Africa is reviewed. We show that mammals are the prime source of bushmeat, and that ungulates and rodents make up the highest proportion of biomass extracted.
• 2 We present data on current knowledge of extraction patterns of wild mammals in West and Central Africa, and evidence that at current off‐take levels, within the range states, mammals as bushmeat are being depleted on an unprecedented scale. Extraction rates are orders of magnitude higher there than in comparable ecosystems like the Amazon, and much less likely to be sustainable.
• 3 However, basic knowledge of the biology of harvestable tropical moist forest mammals, and the consequences of hunting on mammalian communities, which permits accurate estimation of maximal production rate (the excess of growth over replacement rate), is largely unavailable, and this hinders estimation of hunting quotas and sustainability. Comparisons are made with the existing information available on Amazon basin mammals and hunting patterns reported there.

     

Unexpected biodiversity loss under global warming in the neotropical Guayana Highlands: a preliminary appraisal

The fully vegetated summits of the table mountains that form the Guayana Highlands (GH), in northern South America, hold amazing biodiversity and endemism levels, and unique vegetation types. In spite of their present‐day healthy appearance, their biota is seriously threatened of habitat loss by upward displacement, because of the projected warming for the end of this century. Available data are still insufficient for a definite assessment, but preliminary estimations based on representative endemic vascular plant species show that roughly one‐tenth to one‐third of them would loss their habitat with the 2–4°C temperature increase predicted for the region by AD 2100. Given the underlying endemism, the eventual loss of biodiversity will be of global nature. Other mountain ranges around the world with similar characteristics of the GH, namely topographical isolation, high endemism and absence of nival stage because of the lower altitude, would be under similar unexpected risk, and should be urgently considered for conservation purposes.     

History meets ecology: a geographical analysis of ecological restriction in the Neotropical humid montane forests avifaunas

Aim To analyse the ecological patterns of distribution of the avifaunas of the Neotropical humid montane forests, by assessing the degree of habitat restriction among species through the calculation of a numerical index, analysing their relationships with adjacent habitat, and exploring the relative contribution of both higher and lower habitats in shaping the avian assemblages. Location The Neotropical humid montane forests, from Mexico to north‐western Argentina. Methods The degree of species’ restriction to the habitat was calculated through a restriction index based on published endemicity indexes. The index scores range from 0 to 1: a score of 1 indicates a totally endemic species (i.e. fully restricted to the habitat); values tending to 0 indicate a widespread species. Results In Mesoamerica, completely restricted species represent a lower proportion of the total avifauna than in South American humid montane forests; whereas species shared to other habitats showed a higher proportion of the avifauna with affinities to higher altitude forests (e.g. pine and pine‐oak forests). South America, on the other hand, holds assemblages with a high proportion of completely restricted species; species shared to other habitats showed a high proportion of taxa with affinities to lowland forests. Main conclusions The ecological distribution of the HMF's avifauna could be partitioned in three main components: the ecologically restricted avifauna, the high altitude species and, the lower altitude species, which are tightly associated to the floristic composition along the gradient. The history of formation of the HMF flora and the ecological distribution of different avian taxa suggest a common history. Finally, the restriction index allowed a detailed evaluation of the composition of avian assemblages, their degree of restriction to the habitat and of the affinities regarding adjacent habitats, as well as an accurate distinction between species richness and restricted species richness, which should be a fundamental step towards the establishment of conservation priorities.     

Impacts of climate change on the tree line

The possible effects of climate change on the advance of the tree line are considered. As temperature, elevated CO(2) and nitrogen deposition co-vary, it is impossible to disentangle their impacts without performing experiments. However, it does seem very unlikely that photosynthesis per se and, by implication, factors that directly influence photosynthesis, such as elevated CO(2), will be as important as those factors which influence the capacity of the tree to use the products of photosynthesis, such as temperature. Moreover, temperature limits growth more severely than it limits photosynthesis over the temperature range 5-20 degrees C. If it is assumed that growth and reproduction are controlled by temperature, a rapid advance of the tree line would be predicted. Indeed, some authors have provided photographic evidence and remotely sensed data that suggest this is, in fact, occurring. In regions inhabited by grazing animals, the advance of the tree line will be curtailed, although growth of trees below the tree line will of course increase substantially.     

基于系统保护理念的弹性生态保护空间划定——以广东省茂名市为例

有效识别生态保护空间对维护区域生物多样性,提升生态系统服务具有重要作用。考虑山水林田湖草系统保护战略需求以及既往弹性生态保护研究不足,基于可持续发展目标下生态保护概念内涵,系统解析弹性生态保护空间的内在要求;立足生态系统服务视角,以沿海特色发展区——广东省茂名市为研究区,在考虑传统重要生态功能的基础上,基于区域特点选取气候调节功能、粮食供给功能、生物保护功能、水源涵养功能、土壤保护功能5项生态系统服务作为保护对象;通过改进的MARXAN模型提取弹性生态保护空间,并对相关结果的有效性进行了验证。研究结果表明：①茂名市各项生态系统服务空间分布存在差异,综合生态系统服务高值区主要分布在北部山区,低值区主要集中在南部城镇建设区;②考虑限制条件和保护成本的系统保护规划方法在生态保护空间划定上具有一定优势,系统保护规划结果与生态保护红线重叠面积1505.02 km²,占生态保护红线面积的83.43%,其余区域主要由林草地类、园地类、耕地类组成,占比分别为45.92%、19.71%、22.24%;③在未来生态保护建设中,应针对系统保护规划内生态红线核心区、一般保护区、基本农田区分别开展生态保护加强管理、生态系统服务综合提升、生态农业建设等多样化整治策略。     

Plant biodiversity inventory and conservation of two tropical dry evergreen forests on the Coromandel coast, south India

Species diversity, population structure, abundance and dispersion patterns of all woody plants 10cm gbh were inventoried in two 1-ha plots of tropical dry evergreen (sacred grove or temple) forests at Kuzhanthaikuppam (KK) and Thirumanikkuzhi (TM) on the Coromandel coast of south India. Site KK is a stunted forest (average tree height ca 6 m) and TM a tall forest (average tree height ca 10 m). A total of 54 species (in 47 genera and 31 families) were recorded. Species richness and stand density were 42 and 38 species and 1367 and 974 individuals ha–1 respectively for the sites KK and TM. About 50% of the total species were common to both the sites. Site TM is twofold more voluminous (basal area 29.48 m2 ha–1) than KK (basal area 15.44 m2 ha–1). Nearly one third of the individuals are multi-stemmed in the low-statured site KK whereas one fourth of the tree density is multi-stemmed in TM. Species abundance pattern varied between the two sites. The abundance of three species in KK and two species in TM is pronounced. Memecylon umbellatum, the most abundant species contributing to one third of total stand density in KK, is least represented in TM. Species richness, density and diversity indices decreased with increasing girth threshold. Most species exhibited clumped dispersion of individuals both at 0.25 and 1-ha scales. Population structure for girth frequency is an expanding one for both the sites, except for basal area distribution in KK. Variations in plant diversity and abundance are related to site attributes and human impacts. In the light of habitat uniqueness, species richness and sacred grove status, the need for conservation is emphasized.     

The role of land-use history in driving successional pathways and its implications for the restoration of tropical forests

Secondary forests are increasingly important components of human-modified landscapes in the tropics. Successional pathways, however, can vary enormously across and within landscapes, with divergent regrowth rates, vegetation structure and species composition. While climatic and edaphic conditions drive variations across regions, land-use history plays a central role in driving alternative successional pathways within human-modified landscapes. How land use affects succession depends on its intensity, spatial extent, frequency, duration and management practices, and is mediated by a complex combination of mechanisms acting on different ecosystem components and at different spatial and temporal scales. We review the literature aiming to provide a comprehensive understanding of the mechanisms underlying the long-lasting effects of land use on tropical forest succession and to discuss its implications for forest restoration. We organize it following a framework based on the hierarchical model of succession and ecological filtering theory. This review shows that our knowledge is mostly derived from studies in Neotropical forests regenerating after abandonment of shifting cultivation or pasture systems. Vegetation is the ecological component assessed most often. Little is known regarding how the recovery of belowground processes and microbiota communities is affected by previous land-use history. In published studies, land-use history has been mostly characterized by type, without discrimination of intensity, extent, duration or frequency. We compile and discuss the metrics used to describe land-use history, aiming to facilitate future studies. The literature shows that (i) species availability to succession is affected by transformations in the landscape that affect dispersal, and by management practices and seed predation, which affect the composition and diversity of propagules on site. Once a species successfully reaches an abandoned field, its establishment and performance are dependent on resistance to management practices, tolerance to (modified) soil conditions, herbivory, competition with weeds and invasive species, and facilitation by remnant trees. (ii) Structural and compositional divergences at early stages of succession remain for decades, suggesting that early communities play an important role in governing further ecosystem functioning and processes during succession. Management interventions at early stages could help enhance recovery rates and manipulate successional pathways. (iii) The combination of local and landscape conditions defines the limitations to succession and therefore the potential for natural regeneration to restore ecosystem properties effectively. The knowledge summarized here could enable the identification of conditions in which natural regeneration could efficiently promote forest restoration, and where specific management practices are required to foster succession. Finally, characterization of the landscape context and previous land-use history is essential to understand the limitations to succession and therefore to define cost-effective restoration strategies. Advancing knowledge on these two aspects is key for finding generalizable relations that will increase the predictability of succession and the efficiency of forest restoration under different landscape contexts.     

Impacts of climate change on natural forest productivity – evidence since the middle of the 20th century

Changes to forest production drivers (light, water, temperature, and site nutrient) over the last 55 years have been documented in peer‐reviewed literature. The main objective of this paper is to review documented evidence of the impacts of climate change trends on forest productivity since the middle of the 20th century. We first present a concise overview of the climate controls of forest production, provide evidence of how the main controls have changed in the last 55 years, followed by a core section outlining our findings of observed and documented impacts on forest productivity and a brief discussion of the complications of interpreting trends in net primary production (NPP). At finer spatial scales, a trend is difficult to decipher, but globally, based on both satellite and ground‐based data, climatic changes seemed to have a generally positive impact on forest productivity when water was not limiting. Of the 49 papers reporting forest production levels we reviewed, 37 showed a positive growth trend, five a negative trend, three reported both a positive and a negative trend for different time periods, one reported a positive and no trend for different geographic areas, and two reported no trend. Forests occupy ≈52% of the Earth's land surface and tend to occupy more temperature and radiation‐limited environments. Less than 7% of forests are in strongly water‐limited systems. The combined and interacting effects of temperature, radiation, and precipitation changes with the positive effect of CO₂, the negative effects of O₃ and other pollutants, and the presently positive effects of N will not be elucidated with experimental manipulation of one or a few factors at a time. Assessments of the greening of the biosphere depend on both accurate measurements of rates (net ecosystem exchange, NPP), how much is stored at the ecosystem level (net ecosystem production) and quantification of disturbances rates on final net biome production.     

Restoration ecology in the Anthropocene: learning from responses of tropical forests to extreme disturbance events

Extreme disturbance events denote another aspect of global environmental changes archetypal of the Anthropocene. These events of climatic or anthropic origin are challenging our perceived understanding about how forests respond to disturbance. I present a general framework of tropical forest responses to extreme disturbance events with specific examples from tropical dry forests. The linkage between level of disturbance severity and dominant mechanism of vegetation recovery is reflected on a variety of initial trajectories of forest succession. Accordingly, more realistic and cost‐effective restoration goals in many tropical forests likely consist in maintaining a mosaic of different successional trajectories while promoting landscape connectivity, rather than encouraging full‐ecosystem recovery to pre‐disturbance conditions. Incorporating extreme disturbance events into the global restoration ecology agenda will be essential to design well‐informed ecosystem management strategies in the coming decades.