Alfonso Alonso

Scientific Foundations for an IUCN Red List of Ecosystems

An understanding of risks to biodiversity is needed for planning action to slow current rates of decline and secure ecosystem services for future human use. Although the IUCN Red List criteria provide an effective assessment protocol for species, a standard global assessment of risks to higher levels of biodiversity is currently limited. In 2008, IUCN initiated development of risk assessment criteria to support a global Red List of ecosystems. We present a new conceptual model for ecosystem risk assessment founded on a synthesis of relevant ecological theories. To support the model, we review key elements of ecosystem definition and introduce the concept of ecosystem collapse, an analogue of species extinction. The model identifies four distributional and functional symptoms of ecosystem risk as a basis for assessment criteria: A) rates of decline in ecosystem distribution; B) restricted distributions with continuing declines or threats; C) rates of environmental (abiotic) degradation; and D) rates of disruption to biotic processes. A fifth criterion, E) quantitative estimates of the risk of ecosystem collapse, enables integrated assessment of multiple processes and provides a conceptual anchor for the other criteria. We present the theoretical rationale for the construction and interpretation of each criterion. The assessment protocol and threat categories mirror those of the IUCN Red List of species. A trial of the protocol on terrestrial, subterranean, freshwater and marine ecosystems from around the world shows that its concepts are workable and its outcomes are robust, that required data are available, and that results are consistent with assessments carried out by local experts and authorities. The new protocol provides a consistent, practical and theoretically grounded framework for establishing a systematic Red List of the world’s ecosystems. This will complement the Red List of species and strengthen global capacity to report on and monitor the status of biodiversity

Discriminatory power of different arthropod data sets for the biological monitoring of anthropogenic disturbance in tropical forests

Arthropods were monitored by local parataxonomists at 12 sites of increasing anthropogenic disturbance (old and young secondary forests, savanna and cultivated gardens) at Gamba, Gabon. We report on the discriminatory power of different data sets with regard to the classification of sites along the disturbance gradient, using preliminary data accounting for 13 surveys and 142425 arthropods collected by Malaise, pitfall and yellow-pan traps. We compared the performance of different data sets. These were based upon ordinal, familial and guild composition, or upon 22 target taxa sorted to morphospecies and either considered in toto or grouped within different functional guilds. Finally we evaluated ‘predictor sets’ made up of a few families or other target taxa, selected on the basis of their indicator value index. Although the discriminatory power of data sets based on ordinal categories and guilds was low, that of target taxa belonging to chewers, parasitoids and predators was much higher. The data sets that best discriminated among sites of differing degrees of disturbance were the restricted sets of indicator families and target taxa. This validates the concept of predictor sets for species-rich tropical systems. Including or excluding rare taxa in the analyses did not alter these conclusions. We conclude that calibration studies similar to ours are needed elsewhere in the tropics and that this strategy will allow to devise a representative and efficient biotic index for the biological monitoring of terrestrial arthropod assemblages in the tropics.

Impacts of Roads, Hunting, and Habitat Alteration on Nocturnal Mammals in African Rainforests

Nocturnal mammals are poorly studied in Central Africa, a region experiencing dramatic increases in logging, roads, and hunting activity. In the rainforests of southern Gabon, we used spotlighting surveys to estimate abundances of nocturnal mammal species and guilds at varying distances from forest roads and between hunted and unhunted treatments (comparing a 130-km(2) oil concession that was nearly free of hunting, with nearby areas outside the concession that had moderate hunting pressure). At each of 12 study sites that were evenly divided between hunted and unhunted areas, we established standardized 1-km transects along road verges and at 50, 300, and 600 m from the road. We then repeatedly surveyed mammals at each site during 2006. Hunting had few apparent effects on this assemblage. Nevertheless, the species richness and often the abundance of nocturnal primates, smaller ungulates, and carnivores were significantly depressed within approximately 30 m of roads. Scansorial rodents increased in abundance in hunted forests, possibly in response to habitat changes caused by logging or nearby swidden farming. In multiple-regression models many species and guilds were significantly influenced by forest-canopy and understory cover, both of which are altered by logging and by certain abiotic variables. In general, nocturnal species, many of which are arboreal or relatively small in size (<10 kg), were less strongly influenced by hunting and more strongly affected by human-induced changes in forest structure than were larger mammal species in our study area.

Choice of metrics for studying arthropod responses to habitat disturbance: one example from Gabon

Abstract.  1 The choice of metrics comparing pristine and disturbed habitats may not be straightforward. We examined the results of a study in Gabon including 21 arthropod focal taxa representing 16 855 individuals separated into 1534 morphospecies. Replication included the understorey of 12 sites representing four stages of land use after logging (old and young forests, savanna and gardens), surveyed for 1 year using three sampling methods. 2 For all focal taxa, we calculated a suite of 13 metrics accounting for the intensity of faunal changes between habitats, namely: abundance; observed, rarefied and estimated species richness; proportion of rare species; additive diversity partitioning; evenness of assemblages; higher taxonomic composition; species turnover; ordination scores of multivariate analyses; nestedness; proportion of site‐specific species and ratios of functional guilds. 3 Most metrics showed large differences between forests and non‐forest habitats, but were not equally discriminating for particular taxa. Despite higher taxonomic groups being present in most habitats, many insect species were site or habitat specific. There was little evidence that the disturbance gradient represented a series of impoverished habitats derived from older forests. Rather, entire suites of species were being replaced as habitats were modified. 4 Metrics based on species identity had a high sensitivity to disturbance, whereas measurements describing community structure were less discriminating in this regard. We recommend using metrics based on abundance, estimated species richness, species turnover estimated by multivariate analyses and guild structure, to avoid misleading interpretations that may result from comparisons of species richness alone.

Plant diversity increases with the strength of negative density dependence at the global scale

Maintaining tree diversity Negative interaction among plant species is known as conspecific negative density dependence (CNDD). This ecological pattern is thought to maintain higher species diversity in the tropics. LaManna et al. tested this hypothesis by comparing how tree species diversity changes with the intensity of local biotic interactions in tropical and temperate latitudes (see the Perspective by Comita). Stronger local specialized biotic interactions seem to prevent erosion of biodiversity in tropical forests, not only by limiting populations of common species, but also by strongly stabilizing populations of rare species, which tend to show higher CNDD in the tropics. Science, this issue p. 1389; see also p. 1328 A global analysis of ~3000 species and ~2.4 million trees elucidates variations in tree species diversity between tropical and temperate latitudes. Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.

Distribution of a Community of Mammals in Relation to Roads and Other Human Disturbances in Gabon, Central Africa

Abstract We present the first community-level study of the associations of both roads and other human disturbances with the distribution of mammals in Gabon (central Africa). Our study site was in an oil concession within a littoral mosaic landscape. We conducted surveys along 199 line transects and installed camera traps on 99 of these transects to document mammal presence and abundance. We used generalized linear mixed-effect models to document associations between variables related to the ecosystem (land cover, topography, and hydrology), roads (coating, width of rights of way, condition, type of vehicle used on the road, traffic level, affiliation of users, and general type of road), and other human disturbances (urbanization, agriculture, hunting, logging, gathering, and industrial activities) and the abundance or presence of 17 species or groups of mammals including elephant (Loxodonta cyclotis), buffalo (Syncerus caffer), sitatunga (Tragelaphus spekei), red river hog (Potamochoerus porcus), smaller ungulates, gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), side-striped jackal (Canis adustus), carnivores, monkeys, and large rodents. Some types of roads and other human disturbances were negatively associated with the abundance or presence of elephants, buffalos, gorillas, sitatungas, some monkeys, and duikers. The pattern of associations of mammals with roads and other human disturbances was diverse and included positive associations with road presence (red river hog, some monkeys, and duikers), agriculture (sitatunga, small carnivores, and large rodents) and industrial activities (sitatunga, red river hog, red duikers, and side-striped jackal). Our results suggest that the community of mammals we studied was mostly affected by hunting, agriculture, and urbanization, which are facilitated by road presence. We recommend increased regulation of agriculture, hunting, and road building in the area. Distribución de una Comunidad de Mamíferos en Relación a Carreteras y Otras Perturbaciones Humanas en Gabón, Africa Central Resumen Presentamos el primer estudio a nivel de comunidad de la relación entre carreteras y otras perturbaciones humanas con la distribución de mamíferos en Gabón (África central). Nuestro sitio de estudio está dentro de una concesión petrolera en un paisaje litoral heterogéneo. Realizamos muestreos a lo largo de 199 transectos lineales e instalamos cámaras trampa en 99 de ellos para documentar la presencia y abundancia de mamíferos. Utilizamos modelos lineales generalizados con efectos mixtos para documentar las asociaciones entre variables relacionadas con el ecosistema (cobertura de suelo, topografía e hidrología), carreteras (tipo de revestimiento, ancho de derecho de vía, condición, tipo de vehículos que utilizan la carretera, nivel de tráfico, afiliación de los usuarios y el tipo general de carretera) y otras perturbaciones humanas (urbanización, agricultura, caza, tala, recolecta y actividades industriales) y la abundancia o presencia de 17 especies o grupos de mamíferos incluyendo elefantes (Loxodonta cyclotis), búfalo (Syncerus caffer), sitatunga (Tragelaphus spekei), cerdo rojo de río (Potomochoerus porcus), ungulados pequeños, gorila (Gorilla gorilla), chimpancé (Pan troglodytes), chacal con rayas a los lados (Canis adustus), carnívoros, monos y roedores de talla grande. Ciertos tipos de carreteras y otras perturbaciones humanas estuvieron asociadas negativamente con la abundancia o presencia de elefantes, búfalos, gorilas, sitatungas, algunos monos y antílopes. Los patrones de asociación de mamíferos con carreteras y otras perturbaciones humanas fueron diversos e incluyen asociaciones positivas con la presencia de carreteras (cerdo rojo de río, algunos monos y antílopes), agricultura (sitatunga, carnívoros pequeños y roedores de talla grande) y actividades industriales (sitatunga, cerdo rojo de río, antílope rojo y chacal con rayas a los lados). Nuestros resultados sugieren que la comunidad de mamíferos que estudiamos fue afectada principalmente por la caza, agricultura y urbanización, que son facilitadas por la presencia de carreteras. Recomendamos una mayor regulación de la agricultura, caza y construcción de carreteras en el área.

Use of Landsat and SRTM Data to Detect Broad-Scale Biodiversity Patterns in Northwestern Amazonia

Vegetation maps are the starting point for the design of protected areas and regional conservation plans. Accurate vegetation maps are missing for much of Amazonia, preventing the development of effective and compelling conservation strategies. Here we used a network of 160 inventories across northwestern Amazonia to evaluate the use of Landsat and Shuttle Radar Topography Mission (SRTM) data to identify floristic and edaphic patterns in Amazonian forests. We first calculated the strength of the relationship between these remotely-sensed data, and edaphic and floristic patterns in these forests, and asked how sensitive these results are to image processing and enhancement. We additionally asked if SRTM data can be used to model patterns in plant species composition in our study areas. We find that variations in Landsat and SRTM data are strongly correlated with variations in soils and plant species composition, and that these patterns can be mapped solely on the basis of SRTM data over limited areas. Using these data, we furthermore identified widespread patch-matrix floristic patterns across northwestern Amazonia, with implications for conservation planning and study. Our findings provide further evidence that Landsat and SRTM data can provide a cost-effective means for mapping these forests, and we recommend that maps generated from a combination of remotely-sensed and field data be used as the basis for conservation prioritization and planning in these vast and remote forests.

Seasonal drought limits tree species across the Neotropics

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water-stress on the physiological processes of most tree species. This process implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions it predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry-tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the Western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance’ hypothesis has broad applicability in the worlds most species-rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.

Planning an Adaptive Management Process for Biodiversity Conservation and Resource Development in the Camisea River Basin

The Smithsonian Institutions Monitoring and Assessment of Biodiversity Program joined Shell Prospecting and DevelopmentPeru (SPDP) to protect biodiversity during a natural gas exploration project. Emphasis was on long-term societal andenvironmental benefits in addition to financial gain for thecompany. The systematic, cyclical adaptive management process was used to generate feedback for SPDP managers. Adaptive management enables ongoing improvement of management policies and practices based on lessons learned from operational activities. Previous to this study, very little information about the local biodiversity was available. Over a 2-year period, the team conducted biological assessments of six taxonomic groups at five sites located within 600 km2. A broad range of management options such as location,timing and technology were developed from the beginning of theproject. They were considered in conjunction with emerging lessons from the biodiversity assessments. Critical decisions included location of a gas plant and the cost of helicopter access versus roads to service the full field development. Bothof these decisions were evaluated to ensure that they were economically and environmentally feasible. Project design changes, addressed in the planning stage, were accepted once consensus was achieved. Stakeholders were apprised of the implications of the baseline biodiversity assessments.

Framework for Assessment and Monitoring of Biodiversity

Data and information on status and trends of biodiversity are necessary to implement sound conservation and management of species and habitats. Biodiversity monitoring and assessment programs (BMAP) are major components of natural resources management plans, such as those for protected area management and those that integrate natural resource use with sustainable development practices. The BMAP is an effective way to learn how ecosystem components interact and influence one another and provides a framework to evaluate the status and trends in the condition of habitats and species of interest and the effectiveness of management practices.