Question 1

How does active restoration affect carbon recovery in tropical forests?

Accepted Answer

A study in Sabah, Malaysian Borneo combining two decades of permanent-plot data with airborne LiDAR biomass maps found that active restoration accelerated carbon recovery by around 50% compared with natural regeneration. Both active restoration and natural regeneration depended on sustained protection from further disturbance. The study provides a rigorous empirical benchmark for measuring restoration efficacy in logged tropical forests. Comparing restored forest against naturally regenerating forest over two decades is effectively a counterfactual baseline approach, quantifying the additional carbon gains attributable to active restoration interventions.

Question 2

Why does maximising ecosystem services require high species diversity?

Accepted Answer

Research published in Trends in Plant Science found that no single species contributes to all ecosystem functions. Maximising multiple ecosystem services simultaneously requires greater species diversity than optimising any single function, because different species drive different processes. For forest carbon projects, this means that biodiverse restoration designs are more likely to deliver the full range of co-benefits that nature finance increasingly demands.

Question 3

How is aboveground carbon density mapped in tropical forests?

Accepted Answer

A study in Sabah, Malaysian Borneo produced high-resolution aboveground carbon density maps by combining airborne LiDAR with field plot data. The resulting maps guided conservation priorities and restoration investment across degraded and intact forest landscapes. Accurate carbon stock maps are essential for forest carbon project design and baseline setting.

Question 4

Can GEDI spaceborne lidar quantify forest degradation?

Accepted Answer

An evaluation of NASA GEDI in Amazonian rainforests assessed how well spaceborne lidar captures canopy height and biomass variation across forests at different stages of degradation. The study found that GEDI can detect structural differences along degradation gradients, supporting its use in digital MRV systems that monitor forest carbon projects at scale.

Question 5

How can tropical forest canopy height be estimated from remote sensing?

Accepted Answer

Airborne LiDAR produces accurate canopy height maps but is expensive and lacks continuous coverage. This study in tropical forests compared machine learning approaches for predicting canopy height from freely available satellite imagery, finding that open-access Sentinel-2 data combined with Random Forest models performed comparably to more complex approaches using commercial imagery. For forest carbon monitoring, this demonstrates that reliable canopy height estimation does not require expensive data sources or complex deep learning methods.

Question 6

How accurately can beaver population growth be predicted?

Accepted Answer

Population modelling of reintroduced Eurasian beavers in the River Otter catchment, Great Britain, produced growth trajectories that were subsequently confirmed by field surveys, demonstrating the reliability of the modelling approach for informing wildlife management decisions.

Question 7

How reliable are drone photogrammetry surveys for measuring vegetation canopy height under different field conditions?

Accepted Answer

UAV-based structure-from-motion (SfM) photogrammetry is increasingly used by ecologists to measure plant structure and biomass, but its reproducibility under varying operational conditions has not been well characterised. This study found that reconstructed canopy heights are sensitive to wind speed but relatively insensitive to illumination conditions, providing important guidance for survey design. For digital MRV applications, this finding helps practitioners understand which environmental conditions introduce measurement error when using drone surveys to estimate forest biomass and carbon stocks.

Question 8

How do tropical forests respond to climate extremes like excessive rainfall and drought?

Accepted Answer

While climate research has focused heavily on drought impacts, this study found that increased rainfall causing waterlogged soils can also decrease tree growth and survival in aseasonal tropical forests in Malaysia. The research highlights that high rainfall events represent an under-appreciated driver of forest dynamics in regions that are not typically seasonally flooded. Understanding how tropical forests respond to both extremes of the rainfall spectrum is important for accurately modelling carbon stock trajectories under changing climate conditions. These findings are directly relevant to climate adaptation planning, as they show that both drought and flood risk must be considered when projecting forest carbon stability under future climate scenarios. Rigorous science on forest climate responses also strengthens the evidence base for nature finance projects that depend on credible carbon stock projections in a changing climate.

Question 9

What are the long-term biodiversity outcomes of active restoration in selectively logged tropical forests?

Accepted Answer

Active forest restoration can promote the recovery of adult tree species diversity and in particular rare species in selectively logged tropical rainforests. This study in Sabah, Malaysian Borneo compared actively restored forest (climber cutting and enrichment planting with indigenous species) to naturally regenerating areas over two decades following selective logging. Active restoration focusing on biomass production does not need to adversely affect biodiversity, emphasising the potential of restoration to deliver both carbon storage and biodiversity co-benefits. Long-term biodiversity monitoring in restored forests also informs climate adaptation strategies that depend on ecosystem-based approaches to maintain resilient landscapes.

Question 10

What does the evidence say about tree planting outcomes for restoring tropical and sub-tropical Asian forests?

Accepted Answer

This synthesis assesses the contribution of tree planting to ecosystem restoration across tropical and sub-tropical Asia, evaluating evidence on mortality and growth of planted trees at 176 sites and assessing structural and biodiversity recovery of co-located actively restored and naturally regenerating forest plots. Current global policy is driving renewed investment in forest restoration to protect species, sequester carbon, and secure livelihoods, and this review provides a rigorous empirical foundation for setting realistic expectations. For carbon market practitioners, the findings are essential context for evaluating the plausibility of restoration-based carbon project claims in the Asian tropics. This evidence base is equally important for ecosystem-based adaptation, where forest restoration is deployed to maintain ecosystem services, regulate water flows, and build landscape resilience to climate impacts.

Question 11

Can reintroduced beavers coexist with critically endangered water voles, or do they compete for habitat?

Accepted Answer

Water voles are critically endangered in Great Britain and require successful conservation strategies, while Eurasian beavers are being reintroduced across their native range including Great Britain. This study found positive coexistence between the two species, with water vole populations expanding within beaver-engineered wetland habitat, suggesting that beaver reintroduction may benefit rather than harm water vole conservation.

Question 12

How does forest structural heterogeneity affect water reaching the soil surface in regenerating tropical forests?

Accepted Answer

Tropical landscape regeneration affects hydrological ecosystem functioning by regulating the amount of water that reaches the soil surface and altering soil infiltration rates, which in turn affects soil water storage and streamflow. This study examined whether forest heterogeneity influences throughfall in regenerating secondary forests on Borneo, providing insights into the hydrological recovery of logged and restoring landscapes. Understanding hydrological function in regenerating forests is important for assessing the full ecosystem service value of forest carbon projects beyond carbon stocks alone.

Question 13

How does conspecific density dependence affect population dynamics and species coexistence in mast-fruiting tropical forests?

Accepted Answer

Conspecific density dependence (CDD) is a central mechanism proposed to maintain high species richness in tropical forests, but most tests ignore its integrated effects across multiple life stages. Using a 10-year dataset, this study examined the demographic consequences of CDD heterogeneity among mast-fruiting tropical trees, revealing how variation in this process affects long-term population dynamics. Stable tropical tree populations and diverse species assemblages underpin the high and predictable carbon stocks that are fundamental to credible forest carbon baseline assessments.

Question 14

Do dung beetles affect soil water infiltration, and does this matter for forest hydrology?

Accepted Answer

Soil infiltration capacity governs the partitioning of precipitation between infiltration and surface runoff, and is partly determined by macropores created by soil macrofauna. This study found that dung beetle tunnelling activity influences soil infiltration rates in clay-rich soils, demonstrating that invertebrate communities function as hydrological engineers in tropical forest ecosystems. This highlights how ecosystem functioning and the delivery of ecosystem services such as water regulation depend on often-overlooked components of biodiversity.

Question 15

How effective are beaver dams at attenuating flood flows, and what mechanisms drive this effect?

Accepted Answer

Using a Before-After-Control-Impact experimental design, this study quantified the effects of a beaver dam sequence on the flow regime of a stream in SW England, examining the mechanisms that underpin flow attenuation in beaver wetlands. The results contribute to understanding how beaver-engineered landscapes regulate water flows and could support natural flood management strategies.

Question 16

Can UAV photogrammetry accurately estimate aboveground biomass in grasslands, shrublands, and other non-forest ecosystems?

Accepted Answer

Non-forest ecosystems dominated by shrubs, grasses, and herbaceous plants provide important ecosystem services including carbon sequestration, but are poorly represented in existing remotely sensed biomass products. This study demonstrates a globally applicable UAV photogrammetry protocol for predicting aboveground biomass in these ecosystems, filling a critical gap in remote sensing coverage. Extending robust biomass estimation methods to non-forest ecosystems is important for nature-based solutions that span ecosystem types, including carbon projects in grasslands and degraded landscapes.

Question 17

What is at stake for biodiversity and ecosystem services from four decades of tropical forest loss on Borneo?

Accepted Answer

Between 1973 and 2015, approximately 50% of Borneo's forests were lost, largely to oil palm and other industries, placing at risk the vertebrate species — including birds and mammals — that depend on forest habitat. This study quantifies the impacts of this forest loss on functional habitat availability for vertebrate communities, providing rare empirical evidence on how deforestation affects wildlife at landscape scales. The scale of forest loss documented here underscores the importance of robust carbon baselines that can accurately attribute carbon stocks to conservation and restoration interventions. Understanding the consequences of forest loss is also essential context for climate adaptation strategies that depend on maintaining and restoring forest ecosystem services in Southeast Asia.

Question 18

Does genetic diversity within tree species affect seedling growth and survival in tropical rainforests?

Accepted Answer

Where conspecific seedlings occur at high densities, density-dependent processes tend to depress their performance relative to co-occurring heterospecifics. This multispecies study in a Bornean rainforest extends this understanding to within-species genetic diversity and relatedness, testing whether seedling growth and survival are also influenced by the genetic composition of neighbouring conspecifics.

Question 19

Does the importance of individual tree species for ecosystem multifunctionality depend on which services are prioritised?

Accepted Answer

Studies investigating how biodiversity affects ecosystem functioning increasingly focus on multiple functions simultaneously, but few assess the role of species interactions or consider alternative environmental scenarios. This study found that the importance of species identity and interactions for multifunctionality depends significantly on how ecosystem functions are valued, highlighting the context-dependence of biodiversity-ecosystem function relationships. These findings have practical implications for forest restoration projects that seek to maximise specific ecosystem services, including carbon sequestration, under particular environmental conditions.

Question 20

Does tree species diversity increase individual tree growth rates in temperate European forests?

Accepted Answer

Most experimental evidence on biodiversity-ecosystem functioning comes from fast-growing grassland systems; forests have been less well studied despite providing essential ecological services. Using dendrochronology, this study found that forest diversity promotes individual tree growth in central European forest stands, providing empirical support for diversity-productivity relationships in longer-lived systems. Faster individual tree growth in diverse stands has direct implications for carbon accumulation rates, suggesting that biodiversity-informed forest management could enhance carbon sink strength.

Question 21

Do species-diverse forests deliver more stable ecosystem services under environmental variability than monocultures?

Accepted Answer

Testing the insurance hypothesis across the 500 ha Sabah Biodiversity Experiment in Malaysian Borneo, this study analysed seedling mortality and growth in monoculture and mixture plots over the first decade of the experiment. Results reveal key species differences underpinning insurance effects, including a trade-off where denser-wooded species have lower growth rates but higher survival. Survival rates were more extreme in monocultures than mixtures: monocultures of poorly surviving species risk recruitment failure, while monocultures of high-survival species waste limited seedling stocks through self-thinning. Planting diverse mixtures spreads risk and uses seedling stocks more efficiently to restore ecosystem structure and functioning. Biodiversity insurance effects are a core mechanism underpinning ecosystem-based adaptation: diverse forests maintain function when individual species fail under climate stress.

Question 22

How do dipterocarp seedlings adjust their growth and carbon reserves when acclimating to different light environments?

Accepted Answer

Light acclimation is a key driver of tropical forest dynamics and influences the coexistence of dipterocarp species, which dominate the forests of Southeast Asia. This study examined light niche divergence in six dipterocarp species, finding that seedlings can be functionally characterised by their growth rates and non-structural carbohydrate dynamics under different light conditions. Understanding how dipterocarp seedlings respond to light is foundational for designing restoration plantings that will establish successfully in logged forest understories.

Question 23

How do soil warming and elevated CO2 affect vegetation biomass at alpine tree lines?

Accepted Answer

Alpine tree line ecosystems are expected to respond to rising atmospheric CO2 and global warming, but responses are poorly understood. Using a 9-year free-air CO2 enrichment and warming experiment at a Swiss tree line, this study found that both treatments induce biomass shifts in alpine vegetation, with implications for understanding how mountain ecosystems will change under future climate scenarios.

Question 24

Is there a functional trait-based trade-off between growth in high light and survival in low light among tropical tree species?

Accepted Answer

A life-history trade-off between low mortality in shade and rapid growth in high light is one of the most widely accepted mechanisms underlying plant ecological strategies in tropical forests. Using size-specific relative growth rates from 15 tropical tree species, this study provides empirical evidence for how plant functional traits underlie these distinct ecological strategies. Understanding these trade-offs is directly relevant to tropical forest restoration, particularly for selecting appropriate species mixes for restoration plantings in logged forest landscapes with varying light conditions.

Question 25

Do stored carbon reserves help tropical tree seedlings survive drought, and what are the implications for forest resilience under climate change?

Accepted Answer

This study demonstrates that non-structural carbohydrate levels enhance drought survival in tropical tree seedlings, suggesting that internal carbon reserves act as a physiological buffer against water stress. Understanding the mechanisms behind seedling drought survival is important for assessing which species are likely to persist in tropical forests experiencing more frequent drought events under climate change. This research directly informs climate adaptation strategies for tropical forests, identifying the physiological traits that predict species resilience to drought and helping prioritise species for restoration in water-stressed landscapes.

Question 26

How accurately can airborne LiDAR estimate aboveground carbon density in structurally complex tropical forests like those of Borneo?

Accepted Answer

Borneo contains some of the world's most biodiverse and carbon-dense tropical forests, but this island has lost 62% of its old-growth forests over the last 40 years. This study uses airborne laser scanning to estimate aboveground carbon density and quantify its uncertainty across Borneo's structurally complex forests, where conventional allometric approaches are particularly challenging. Rigorous uncertainty quantification for LiDAR-derived carbon estimates is essential for credible carbon baseline assessments and forest carbon credit verification.

Question 27

Do forests with more tree species provide higher levels of multiple ecosystem services simultaneously?

Accepted Answer

Biodiversity is suggested to positively influence multiple ecosystem services, but evidence from natural systems at management-relevant scales has been scarce. Across a 400,000 km² study area, this study found that forests with more tree species supported higher levels of ecosystem multifunctionality — multiple ecosystem services delivered simultaneously — providing landscape-scale empirical support for biodiversity-multifunctionality relationships. For nature-based solutions and carbon markets, this finding supports the co-benefits case for biodiversity-rich forest restoration: higher species diversity is associated not only with ecological richness but also with greater carbon storage and other services valued by investors. This evidence also supports ecosystem-based adaptation strategies: forests with higher species diversity deliver a broader portfolio of ecosystem services, including those critical for climate resilience such as water regulation, soil protection, and habitat connectivity.

Question 28

How do changes in rainfall frequency affect germination and seedling establishment of shade-tolerant dipterocarp trees in Borneo?

Accepted Answer

Climate change is altering rainfall patterns in historically everwet tropical rainforests, with potential consequences for plant regeneration dynamics. This study found differential species responses to infrequent rainfall, suggesting that altered rainfall regimes may influence seed germination and seedling establishment patterns among dipterocarp species in Borneo. Changes in dipterocarp recruitment dynamics have long-term implications for the species composition and carbon density of recovering logged forests. Understanding how altered rainfall regimes affect tree recruitment is essential for climate adaptation in tropical forestry, as species composition shifts will affect both carbon storage capacity and the resilience of forest ecosystem services.

Question 29

Do dipterocarp species partition the forest light environment, and does this explain their coexistence in tropical rainforests?

Accepted Answer

Explaining the coexistence of large numbers of rainforest tree species remains a central challenge in tropical ecology, and light partitioning is one proposed mechanism. Using size-specific relative growth rates for 21 dipterocarp species, this study provides evidence for light-based regeneration niches, with species showing differential growth performance across the light gradient. This growth modelling approach is relevant for designing species-diverse restoration plantings that replicate natural coexistence mechanisms in logged forests.

Question 30

Does selective logging disrupt the density-dependent seed predation processes that maintain species diversity in Southeast Asian rainforests?

Accepted Answer

Much of the remaining forest in Southeast Asia has been selectively logged, and the processes promoting species coexistence — including the Janzen-Connell mechanism, where specialised natural enemies such as seed predators limit conspecific dominance — may be key to the recovery and maintenance of diversity in these forests. This study examines how logging affects density-dependent predation of dipterocarp seeds, assessing whether this coexistence mechanism remains functional after disturbance. The persistence of natural diversity-maintaining processes in logged forests affects their capacity to recover high species richness and, ultimately, the diverse species assemblages that support stable carbon stocks.

Question 31

What is the Sabah Biodiversity Experiment, and what does it aim to discover about tree diversity and forest restoration?

Accepted Answer

The Sabah Biodiversity Experiment is a large-scale, long-term field study on Borneo designed to understand the relationship between tree species diversity and ecosystem functioning in restored tropical forests. The experiment was established to fill a critical knowledge gap: relatively little was known about how biodiversity affects forest structure and functioning in tropical systems, particularly in the context of restoration on degraded logged land. This long-term research programme provides the empirical foundation underpinning understanding of how restoration planting design — including species diversity — influences carbon recovery in Southeast Asian logged forests. The experiment also generates long-term evidence on how species-diverse restoration plantings perform under climate variability — a critical question for ecosystem-based adaptation in tropical regions.

Question 32

What ecosystem services do logged tropical forests provide to local communities, and how do communities prioritise them?

Accepted Answer

Logged forests are more widespread than old-growth forests and harbour substantial biodiversity and carbon stores, yet conservation strategies have largely focused on protecting primary forest. In Borneo, logged forests support the livelihoods of half a million indigenous people. This study in Sabah, Malaysian Borneo investigated how community members value ecosystem services through interviews and ranking exercises. Clean water, clean air, and regulation of temperature, flooding and erosion were ranked as the most important services by all community members regardless of background. Prioritisation of other services varied by age, gender, ethnicity, dependence on forest resources and distance to forest. Critically, communities' priorities align with the ecological literature showing that logged forests retain these services. For climate adaptation, this finding is significant: the ecosystem services communities most depend on for climate resilience — water regulation, temperature moderation, flood and erosion control — are maintained by logged forests, strengthening the case for community-centred conservation of these landscapes.

Research

Featured Publications

Estimating canopy height in tropical forests: Integrating airborne LiDAR and multi-spectral optical data with machine learning

Evaluating GEDI for quantifying forest structure across a gradient of degradation in Amazonian rainforests

Monitoring, modelling and managing beaver (Castor fiber) populations in the River Otter catchment, Great Britain

Active restoration accelerates the carbon recovery of human-modified tropical forests

When Do More Species Maximize More Ecosystem Services?

Mapped aboveground carbon stocks to advance forest conservation and recovery in Malaysian Borneo

All Publications

Estimating canopy height in tropical forests: Integrating airborne LiDAR and multi-spectral optical data with machine learning

Evaluating GEDI for quantifying forest structure across a gradient of degradation in Amazonian rainforests

Repeated drone photogrammetry surveys demonstrate that reconstructed canopy heights are sensitive to wind speed but relatively insensitive to illumination conditions

Tree growth and survival are more sensitive to high rainfall than drought in an aseasonal forest in Malaysia

Biodiversity consequences of long-term active forest restoration in selectively-logged tropical rainforests

The road to recovery: a synthesis of outcomes from ecosystem restoration in tropical and sub-tropical Asian forests

Positive coexistence of water voles and beaver: water vole expansion in a beaver engineered wetland

Does forest heterogeneity affect mean throughfall for regenerating secondary forests on Borneo?

Demographic consequences of heterogeneity in conspecific density dependence among mast-fruiting tropical trees

Dung beetles as hydrological engineers: effects of tunnelling on soil infiltration

The value of logged tropical forests: A study of ecosystem services in Sabah, Borneo

Exploring the dynamics of flow attenuation at a beaver dam sequence

Monitoring, modelling and managing beaver (Castor fiber) populations in the River Otter catchment, Great Britain

Exploring the causes of flow attenuation at a beaver dam sequence.

Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non‐forest ecosystems

Beaver: Nature's ecosystem engineers

Active restoration accelerates the carbon recovery of human-modified tropical forests

Impacts of Four Decades of Forest Loss on Vertebrate Functional Habitat on Borneo

Exploring the role of genetic diversity and relatedness in tree seedling growth and mortality: A multispecies study in a Bornean rainforest

Drone-derived canopy height predicts biomass across non-forest ecosystems globally

When Do More Species Maximize More Ecosystem Services?

Estimating aboveground carbon density and its uncertainty in Borneo's structurally complex tropical forests using airborne laser scanning

Estimating aboveground carbon density and its uncertainty in Borneo’s structurally complex tropical forests using airborne laser scanning

Supplementary material to "Estimating aboveground carbon density and its uncertainty in Borneo’s structurally complex tropical forests using airborne laser scanning"

Mapped aboveground carbon stocks to advance forest conservation and recovery in Malaysian Borneo

The importance of species identity and interactions on multifunctionality depends on how ecosystem functions are valued.

Forest diversity promotes individual tree growth in central European forest stands

The value of biodiversity for the functioning of tropical forests: insurance effects during the first decade of the Sabah biodiversity experiment

Growth rates and relative change in non-structural carbohydrates of dipterocarp seedlings in response to light acclimation

Globally, functional traits are weak predictors of juvenile tree growth, and we do not know why

Soil warming and CO 2 enrichment induce biomass shifts in alpine tree line vegetation

A trait‐based trade‐off between growth and mortality: evidence from 15 tropical tree species using size‐specific relative growth rates

Drought survival of tropical tree seedlings enhanced by non-structural carbohydrate levels

Higher levels of multiple ecosystem services are found in forests with more tree species

The Influence of Variable Rainfall Frequency on Germination and Early Growth of Shade-Tolerant Dipterocarp Seedlings in Borneo

Differential growth responses in seedlings of ten species of Dipterocarpaceae to experimental shading and defoliation

Light-based Regeneration Niches: Evidence from 21 Dipterocarp Species using Size-specific RGRs

Plant growth rates and seed size: a re-evaluation

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest.

The Sabah Biodiversity Experiment: a long-term test of the role of tree diversity in restoring tropical forest structure and functioning.

Positive effects of ectomycorrhizal colonization on growth of seedlings of a tropical tree across a range of forest floor light conditions

Effects of Seed Predators of Different Body Size on Seed Mortality in Bornean Logged Forest

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