Charles J. Marsh

Tropical Asia hosts an exceptionally diverse and unique biota, but comprehensive estimates of species diversity and endemism are unavailable for its many subregions, and gaps in biodiversity knowledge and conservation assessments remain unexplored. Here, we synthesize biodiversity data from tropical Asia to assess patterns of species richness, endemism, data completeness, species discovery, and extinction risk across major plant and animal groups. We show that the Asian tropics harbour nearly one quarter of the known global diversity among taxa examined on average while being much smaller in extent than other tropical realms, probably due to its insular and archipelagic geography. Rates of species discovery remain high for many terrestrial and freshwater groups especially in Indochina, South Asia and Borneo, indicating substantial undocumented diversity. Considerable spatiotemporal shortfalls in species occurrence data exist, particularly across Indonesia. Among assessed species, about one-third of vascular plants, one fifth of the land and freshwater vertebrate fauna, one-third of reef-building corals, and almost half of the region’s shark and ray species are threatened with extinction. However, conservation assessments are lacking for many invertebrate species, and almost one-sixth of assessments are over a decade old and thus may not be keeping pace with intensifying human pressures across the region. Our analysis highlights the critical need for increased investment and effort to better document, monitor, study, and safeguard tropical Asia’s rich natural heritage.

Emerging evidence shows that responses to deforestation can differ both across species and among populations of the same species. The reasons underlying these complex patterns are unclear, and this lack of clarity is a barrier to accurate monitoring and prediction of biodiversity change. Using data from 2,262 bird species across 7,326 sites from all forested continents, we show that between-species and within-species variations in responses to forest cover are mediated by temperature. Populations in warmer macroclimates tend to decline in incidence in deforested landscapes because hotter microclimates push them closer to their species’ realized upper thermal tolerance limits. By contrast, populations in cooler macroclimates tend to be less affected by or even benefit from deforestation, as microclimatic temperatures are pushed closer to more optimal temperatures. Our findings offer an empirically grounded framework for biodiversity models that move beyond fixed species responses and incorporate interactions between temperature and land-use change.

Old‐growth forests in Southeast Asia are dominated by trees of the Dipterocarpaceae family which are targeted by selective logging. Their traits (supra‐annual mast fruiting, limited dispersal, and recalcitrant seeds that form no seed bank) mean they can have poor natural regeneration rates in some selectively logged forests. Enrichment planting is used to attempt to overcome this recruitment limitation and increase restoration success. However, it is still unclear what factors influence the performance of planted seedlings. Here, we analyse the growth and survival between 2012 and 2015 of 721 enrichment line‐planted seedlings from 16 species of dipterocarps within the selectively logged forest of the Sabah Biodiversity Experiment, alongside the location, size and identity of nearly 5000 naturally occurring trees within 10 m of focal planted seedlings. We analysed the survival and growth of enrichment planted dipterocarp seedlings in relation to three properties of the surrounding naturally occurring vegetation: (1) canopy openness; (2) the abundance of naturally occurring dipterocarps (proportion of total basal area); (3) the presence of nearby (< 10 m) large trees (basal area of the largest tree as a proportion of the total). Survival and growth rates of enrichment planted seedlings were positively associated with canopy openness and total basal area of surrounding trees. These results were consistent between the two planting cohorts. Increased survival and growth of enrichment planted seedlings in areas of Sabah Biodiversity Experiment with higher canopy openness (up to around 40%) is consistent with understory light as a limiting resource. The unexpected higher survival and growth of enrichment planted seedlings in forest areas with higher basal area of unlogged trees may be explained by the creation of patches that are better or worse for tree growth, with areas less heavily impacted by logging containing both more naturally occurring trees and providing better conditions for the survival and growth of planted seedlings.

The impacts of degradation and deforestation on tropical forests are poorly understood, particularly at landscape scales. We present an extensive ecosystem analysis of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 82 variables categorized into four ecological levels spanning a broad suite of ecosystem properties: (i) structure and environment, (ii) species traits, (iii) biodiversity, and (iv) ecosystem functions. Responses were highly heterogeneous and often complex and nonlinear. Variables that were directly impacted by the physical process of timber extraction, such as soil structure, were sensitive to even moderate amounts of logging, whereas measures of biodiversity and ecosystem functioning were generally resilient to logging but more affected by conversion to oil palm plantation.

Old-growth forests in Southeast Asia are dominated by trees of the Dipterocarpaceae family which are targeted by selective logging. Their traits (supra-annual mast fruiting, limited dispersal, and recalcitrant seeds that form no seed bank) mean they can have poor natural regeneration rates in some selectively logged forests. Enrichment planting is commonly used to overcome recruitment limitation and increase restoration success. However, it is still unclear what factors influence the success rate of planted seedlings, including the characteristics of the surrounding tree matrix and local neighbourhood. Here, we examine the growth and survival of 721 enrichment line-planted seedlings within 24 plots of the selectively logged forest of the Sabah Biodiversity Experiment, in Malaysian Borneo, in relation to their species identity and local neighbourhoods. We mapped the spatial location, size, and identity of nearly 5,000 surrounding matrix trees (≥ 10 cm diameter at breast height (DBH)) within a 10 m radius of focal planted seedlings in 2012 and 2015. We analysed levels of tree density-dependence, asymmetric competition with naturally occurring trees, and confamilial density-dependence for each seedling. Survival and growth rates of enrichment planted seedlings were positively associated with canopy openness and total basal area of the surrounding tree matrix. These results were consistent between two planting cohorts. Increased survival and growth of enrichment planted seedlings in areas of the Sabah Biodiversity Experiment with higher canopy openness (up to around 40%) is consistent with understory light as a limiting resource. The unexpected higher survival and growth of enrichment planted seedlings in forest areas with higher basal area of unlogged remnant trees may be explained by the logging-induced creation of patches with varying local conditions, with those less heavily impacted by logging containing more naturally occurring trees, greater moderation of extreme high temperature and low humidity, more established mycorrhiza and reduced soil compaction.

We welcome feedback on the range maps published in Marsh et al. (2022) where it constructively improves our knowledge on species distributions. Unfortunately, we are concerned that criticisms raised by Arbogast and Kerhoulas are steps backward, not forward, particularly as they did not access the original range map data of Marsh et al. (2022). We stress that evaluating range maps using Global Biodiversity Information Facility data without the necessary quality control and filtering will lead to flawed interpretations—using the same approach, an even greater proportion, >99.5%, of IUCN mammal range maps would fail to meet their expectations. We take this opportunity to highlight the fine-scale inaccuracies, scale limitations, and range map variance that are expected across all expert range map sources and that any researcher should consider during any analysis. Finally, we again announce the availability of an online tool for providing annotations and proposing adjustments to range maps, and suggest this as a more appropriate forum for constructively and transparently improving range maps.

Geographic range size is the most commonly implemented criterion of species’ extinction risk used in IUCN Red List assessments, especially for poorly-recorded species. IUCN applies two contrasting range size measures to capture different facets of a species’ distribution: Extent of Occurrence (EOO; Criterion B1) is the area bounding all known occurrences and is a proxy for the spatial autocorrelation of risk, while the Area of Occupancy (AOO; Criterion B2) is the area occupied within this boundary and is related to population size at finer grains. Various methods have been proposed to measure both EOO and AOO. We evaluate the impact of applying four methods for each of Criterion B1 and of B2, as well as key parameter choices, on the Red List status of 227 poorly-recorded neotropical pteridophyte species. Between 2 and 100% of species would be considered threatened depending on methodology. The minimum convex polygon method of estimating EOO was relatively robust to sampling effort for all but the least-recorded species. The IUCN-recommended method for estimating AOO of summing occupied 2 × 2 km grid cells was very strongly correlated with the total number of records. It is likely that only a small fraction of species can be adequately assessed using this method, and we recommend caution applying the method to poorly-recorded species in particular, where models predicting occupancy in unsampled areas (e.g. species distribution models) may provide more accurate assessments. It is vital that methodological information is retained with assessments, and comparisons should only be made between assessments utilising equivalent methods.

Tropical forests are threatened by degradation and deforestation but the consequences for these ecosystems are poorly understood, particularly at the landscape scale. We present the most extensive ecosystem analysis to date of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 79 variables categorized into four hierarchical ecological ‘levels’: 1) structure and environment, 2) species traits, 3) biodiversity and 4) ecosystem functions. Variables at the lowest levels that were directly impacted by the physical processes of timber extraction, such as soil characteristics, were sensitive to even moderate amounts of logging, whereas biodiversity and ecosystem functions proved remarkably resilient to logging in many cases, but were more affected by conversion to oil palm plantation. One-Sentence Summary Logging tropical forest mostly impacts structure while biodiversity and functions are more vulnerable to habitat conversion