Toward an integrated monitoring framework to assess the effects of tropical forest degradation and recovery on carbon stocks and biodiversity

Tropical forests harbor a significant portion of global biodiversity and are a critical component of the climate system. Reducing deforestation and forest degradation contributes to global climate‐change mitigation efforts, yet emissions and removals from forest dynamics are still poorly quantified. We reviewed the main challenges to estimate changes in carbon stocks and biodiversity due to degradation and recovery of tropical forests, focusing on three main areas: (1) the combination of field surveys and remote sensing; (2) evaluation of biodiversity and carbon values under a unified strategy; and (3) research efforts needed to understand and quantify forest degradation and recovery. The improvement of models and estimates of changes of forest carbon can foster process‐oriented monitoring of forest dynamics, including different variables and using spatially explicit algorithms that account for regional and local differences, such as variation in climate, soil, nutrient content, topography, biodiversity, disturbance history, recovery pathways, and socioeconomic factors. Generating the data for these models requires affordable large‐scale remote‐sensing tools associated with a robust network of field plots that can generate spatially explicit information on a range of variables through time. By combining ecosystem models, multiscale remote sensing, and networks of field plots, we will be able to evaluate forest degradation and recovery and their interactions with biodiversity and carbon cycling. Improving monitoring strategies will allow a better understanding of the role of forest dynamics in climate‐change mitigation, adaptation, and carbon cycle feedbacks, thereby reducing uncertainties in models of the key processes in the carbon cycle, including their impacts on biodiversity, which are fundamental to support forest governance policies, such as Reducing Emissions from Deforestation and Forest Degradation.     

Deforestation and Benthic Indicators: How Much Vegetation Cover Is Needed to Sustain Healthy Andean Streams?

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.     

A bioregional analysis of the distribution of rainforest cover,deforestation and degradation in Papua New Guinea

Papua New Guinea (PNG) is an extensively forested country. Recent research suggests that despite commencing a trajectory of deforestation and degradation later than many counties in the Asia–Pacific region, PNG is now undergoing comparable rates of forest change. Here we explore the bioregional distribution of changes in the forest estate over the period 1972–2002 and examine their implications for forest protection. This is undertaken through the development of a novel bioregional classification of the country based on biogeographic regions and climatic zones, and its application to existing forest cover and forest‐cover change data. We found that degradation and deforestation varied considerably across the 11 defined biogeographic regions. We report that the majority of deforestation and degradation has occurred within all the lowland forests, and that it is these forests that have the greatest potential for further losses in the near term. The largest percentage of total change occurred in the east of PNG, in the islands and lowlands of the Bismarck, D'Entrecasteaux, East Papuan Islands and in the South‐East Papua–Oro region. The only region with a significant highlands component to undergo deforestation at a comparable magnitude to the islands and lowland regions was the Huon Peninsula and Adelbert region. Significant changes have also occurred at higher elevations, especially at the interface of subalpine grasslands and upper montane forests. Lower montane forests have experienced proportionally less change, yet it is these forests that constitute the majority of forests enclosed within the protected area system. We find that protected areas are not convincingly protecting either representative areas of PNG's ecosystems, nor the forests within their borders. We conclude by suggesting a more expansive and integrated approach to managing the national forest estate.     

Riparian forest indicators of potential future stream condition

Large wood in streams can play an extraordinarily important role in influencing the physical structure of streams and in providing habitat for aquatic organisms. Since wood is continually lost from streams, predicting the future input of wood to streams from riparian forests is crucial to assessing or managing stream ecosystems. Unfortunately, regional monitoring protocols have no established capacity to provide this information. The goal of this research is to propose one or more methods that could meet this need. This goal is pursued by using stream wood delivery models to aid in the design of a monitoring method. Two questions are asked. First, does simpler data change model predictions of future contributions of wood from riparian ecosystems to the stream? The answers to this first question enable monitoring design to be tailored to details affecting estimates of future stream condition. These answers are important, because more detailed data is typically more costly. Second, which metrics, if any, correlate well with model predictions? If such metrics can be identified, then these measures can serve as effective indicators of ecosystem function directly, without using ecosystem models.These questions were addressed by collecting highly detailed field observations of riparian forests from 109 forested riparian sites in the Coast Range, Willamette Valley, and western Cascades of northwestern Oregon. Detailed and simplified versions of these data were used in models that forecast the potential of riparian forests to provide wood to the stream. Model predictions with less detailed data typically provided answers different than did predictions made with more detailed data. Thus, ecosystem assessments requiring these types of model predictions would benefit from more detailed data. In contrast, riparian metrics easily observed in the field (e.g. number of basal area of trees) or derived from remotely sensed imagery (e.g. number or height of canopy trees) were well correlated with model predictions of potential stream wood recruitment. When direct model predictions or model scenario analyses are not required, these metrics can serve as effective indicators of the potential of riparian forests to provide wood to the future stream network.     

Design and Implementation of an Interactive Web-Based Near Real-Time Forest Monitoring System

This paper describes an interactive web-based near real-time (NRT) forest monitoring system using four levels of geographic information services: 1) the acquisition of continuous data streams from satellite and community-based monitoring using mobile devices, 2) NRT forest disturbance detection based on satellite time-series, 3) presentation of forest disturbance data through a web-based application and social media and 4) interaction of the satellite based disturbance alerts with the end-user communities to enhance the collection of ground data. The system is developed using open source technologies and has been implemented together with local experts in the UNESCO Kafa Biosphere Reserve, Ethiopia. The results show that the system is able to provide easy access to information on forest change and considerably improves the collection and storage of ground observation by local experts. Social media leads to higher levels of user interaction and noticeably improves communication among stakeholders. Finally, an evaluation of the system confirms the usability of the system in Ethiopia. The implemented system can provide a foundation for an operational forest monitoring system at the national level for REDD+ MRV applications.     

Land cover change 2002–2005 in Borneo and the role of fire derived from MODIS imagery

Borneo has experienced heavy deforestation and forest degradation during the past two decades. In this study the Moderate Resolution Imaging Spectroradiometer was used to monitor land cover change in Borneo between 2002 and 2005 in order to assess the current extent of the forest cover, the deforestation rate and the role of fire. Using Landsat and ground observation for validation it was possible to discriminate 11 land cover classes. In 2002 57% of the land surface of Borneo was covered with forest of which 74% was dipterocarp and more than 23% peat swamp forest. The average deforestation rate between 2002 and 2005 was 1.7% yr^{− 1}. The carbon-rich ecosystem of peat swamp forests showed a deforestation rate of 2.2%. Almost 98% of all deforestation occurred within a range of 5 km to the forest edge. Fire is highly correlated with land cover changes. Most fires were detected in degraded forests. Ninety-eight per cent of all forest fires were detected in the 5 km buffer zone, underlining that fire is the major driver for forest degradation and deforestation.     

National forest cover change in Congo Basin: deforestation,reforestation, degradation and regeneration for the years 1990, 2000 and 2005

This research refers to an object‐based automatic method combined with a national expert validation to produce regional and national forest cover change statistics over Congo Basin. A total of 547 sampling sites systematically distributed over the whole humid forest domain are required to cover the six Central African countries containing tropical moist forest. High resolution imagery is used to accurately estimate not only deforestation and reforestation but also degradation and regeneration. The overall method consists of four steps: (i) image automatic preprocessing and preinterpretation, (ii) interpretation by national expert, (iii) statistic computation and (iv) accuracy assessment. The annual rate of net deforestation in Congo Basin is estimated to 0.09% between 1990 and 2000 and of net degradation to 0.05%. Between 2000 and 2005, this unique exercise estimates annual net deforestation to 0.17% and annual net degradation to 0.09%. An accuracy assessment reveals that 92.7% of tree cover (TC) classes agree with independent expert interpretation. In the discussion, we underline the direct causes and the drivers of deforestation. Population density, small‐scale agriculture, fuelwood collection and forest's accessibility are closely linked to deforestation, whereas timber extraction has no major impact on the reduction in the canopy cover. The analysis also shows the efficiency of protected areas to reduce deforestation. These results are expected to contribute to the discussion on the reduction in CO₂ emissions from deforestation and forest degradation (REDD+) and serve as reference for the period.     

Deforestation Trends of Tropical Dry Forests in Central Brazil

Tropical dry forests are the most threatened forest type in the world yet a paucity of research about them stymies development of appropriate conservation actions. The Paranã River Basin has the most significant dry forest formations in the Cerrado biome of central Brazil and is threatened by intense land conversion to pastures and agriculture. We examined changes in Paranã River Basin deforestation rates and fragmentation across three time intervals that covered 31 yr using Landsat imagery. Our results indicated a 66.3 percent decrease in forest extent between 1977 and 2008, with an annual rate of forest cover change of 3.5 percent. Landscape metrics further indicated severe forest loss and fragmentation, resulting in an increase in the number of fragments and reduction in patch sizes. Forest fragments in flatlands have virtually disappeared and the only significant forest remnants are mostly found over limestone outcrops in the eastern part of the basin. If current patterns persist, we project that these forests will likely disappear within 25 yr. These patterns may be reversed with creation of protected areas and involvement of local people to preserve small fragments that can be managed for restoration.     

Characterizing a tropical deforestation wave: a dynamic spatial analysis of a deforestation hotspot in the Colombian Amazon

Tropical deforestation is the major contemporary threat to global biodiversity, because a diminishing extent of tropical forests supports the majority of the Earth's biodiversity. Forest clearing is often spatially concentrated in regions where human land use pressures, either planned or unplanned, increase the likelihood of deforestation. However, it is not a random process, but often moves in waves originating from settled areas. We investigate the spatial dynamics of land cover change in a tropical deforestation hotspot in the Colombian Amazon. We apply a forest cover zoning approach which permitted: calculation of colonization speed; comparative spatial analysis of patterns of deforestation and regeneration; analysis of spatial patterns of mature and recently regenerated forests; and the identification of local‐level hotspots experiencing the fastest deforestation or regeneration. The colonization frontline moved at an average of 0.84 km yr^?1 from 1989 to 2002, resulting in the clearing of 3400 ha yr^?1 of forests beyond the 90% forest cover line. The dynamics of forest clearing varied across the colonization front according to the amount of forest in the landscape, but was spatially concentrated in well‐defined ‘local hotspots’ of deforestation and forest regeneration. Behind the deforestation front, the transformed landscape mosaic is composed of cropping and grazing lands interspersed with mature forest fragments and patches of recently regenerated forests. We discuss the implications of the patterns of forest loss and fragmentation for biodiversity conservation within a framework of dynamic conservation planning.     

Declining Amazon biomass due to deforestation and subsequent degradation losses exceeding gains

In the Amazon, deforestation and climate change lead to increased vulnerability to forest degradation, threatening its existing carbon stocks and its capacity as a carbon sink. We use satellite L-Band Vegetation Optical Depth (L-VOD) data that provide an integrated (top-down) estimate of biomass carbon to track changes over 2011–2019. Because the spatial resolution of L-VOD is coarse (0.25°), it allows limited attribution of the observed changes. We therefore combined high-resolution annual maps of forest cover and disturbances with biomass maps to model carbon losses (bottom-up) from deforestation and degradation, and gains from regrowing secondary forests. We show an increase of deforestation and associated degradation losses since 2012 which greatly outweigh secondary forest gains. Degradation accounted for 40% of gross losses. After an increase in 2011, old-growth forests show a net loss of above-ground carbon between 2012 and 2019. The sum of component carbon fluxes in our model is consistent with the total biomass change from L-VOD of 1.3 Pg C over 2012-2019. Across nine Amazon countries, we found that while Brazil contains the majority of biomass stocks (64%), its losses from disturbances were disproportionately high (79% of gross losses). Our multi-source analysis provides a pessimistic assessment of the Amazon carbon balance and highlights the urgent need to stop the recent rise of deforestation and degradation, particularly in the Brazilian Amazon.     

Forest carbon in lowland Papua New Guinea: Local variation and the importance of small trees

Efforts to incentivize the reduction of carbon emissions from deforestation and forest degradation require accurate carbon accounting. The extensive tropical forest of Papua New Guinea (PNG) is a target for such efforts and yet local carbon estimates are few. Previous estimates, based on models of neotropical vegetation applied to PNG forest plots, did not consider such factors as the unique species composition of New Guinea vegetation, local variation in forest biomass, or the contribution of small trees. We analysed all trees >1 cm in diameter at breast height (DBH) in Melanesia's largest forest plot (Wanang) to assess local spatial variation and the role of small trees in carbon storage. Above‐ground living biomass (AGLB) of trees averaged 210.72 Mg ha^?1 at Wanang. Carbon storage at Wanang was somewhat lower than in other lowland tropical forests, whereas local variation among 1‐ha subplots and the contribution of small trees to total AGLB were substantially higher. We speculate that these differences may be attributed to the dynamics of Wanang forest where erosion of a recently uplifted and unstable terrain appears to be a major source of natural disturbance. These findings emphasize the need for locally calibrated forest carbon estimates if accurate landscape level valuation and monetization of carbon is to be achieved. Such estimates aim to situate PNG forests in the global carbon context and provide baseline information needed to improve the accuracy of PNG carbon monitoring schemes.     

Forest transition in an ecologically important region: Patterns and causes for landscape dynamics in the Niger Delta

The influence of human related actives such as oil and gas exploration, intensified logging of trees and over exploitation of forest resources for food, have negatively impacted the once flourishing and ecologically diverse forest system of the Niger Delta region in Nigeria. Relevant information on the transitional changes of forested landscapes in the delta is poor compared to other tropical forests such as the Brazilian and Columbian Amazonian forest where numerous research studies have been conducted. Consequently, this study aimed at investigating the spatial extent and rates of forest transition in the Niger Delta region taking into consideration the patterns, causes and implications of the landscape dynamics. The study determined the spatial extent and rates of forest transition in the study area using remotely sensed data from 1986 and 2007. The results indicated that the spatial extent of deforestation, unchanged forest cover and afforestation were 1.38, 2.39, and 1.15 million hectares, respectively, while the annual deforestation and afforestation rates were 0.95 and 0.75% which are high compared to other areas in the humid tropics. The annual rate of change in forest cover was determined as ?0.13% indicating an overall reduction in the spatial extent of forest cover for the entire delta. Changes in the spatial structure of forests were investigated using landscape metrics and the results showed there was a substantial increase in forest fragmentation. The variations in population dynamics and poverty indicators between different states of the Niger Delta were unable to explain the observed patterns of forest change. Instead, the authors observed that the main determinants of forest dynamics were the variations in state forest management policies and the influence of the oil and gas industry on the economies of the states. High rates of afforestation were found in states that have limited oil resources and were more economically dependent on forest products, while states with high deforestation rates were found in the main oil-producing parts of the study site. Using the present trend of forest transition dynamics, a 20-year forward simulation was generated using the Markov algorithm. The results concerning forest transition in the study area point to the urgent need for appropriate environmental policy development and implementation for the Niger Delta region.     

Can engaging local people’s interests reduce forest degradation in Central Vietnam?

Governments in tropical countries are still responding to increasing forest degradation by implementing different types of protected areas. In general, due to their negative image as causes of deforestation, local communities are being excluded from any management role in these conservation areas. However, in Vietnam, since 1986 various incentives have been proposed for alternative conservation models. Our surveys used a multidisciplinary combination of methods to work with one Pahy ethnic minority around the degraded forests of the proposed Phong Dien Nature Reserve in Central Vietnam. From the results of these surveys we obtained clear indication that conservation can be enhanced if local priorities, perspectives and wishes are better identified and taken into account. The local communities identified the need for, at least, limited extractive activities in the protected area. They also frequently stressed their willingness to participate in the monitoring and control of the area, and in the selection of local species for reforestation programmes. Communities can and should be actively involved in building a shared understanding of what the forest provides, how it can be conserved and the benefits to be obtained. Conservation in Vietnam has much to gain from local participation. However, suitable safeguards and incentives need to be in place to insure sustainable use of the forest resources.     

Spatial and temporal deforestation dynamics in protected and unprotected dry forests: a case study from Myanmar (Burma)

Tropical dry forests are more threatened, less protected and especially susceptible to deforestation. However, most deforestation research focuses on tropical rain forests. We analyzed spatial and temporal changes in land cover from 1972 through 2005 at Chatthin Wildlife Sanctuary (CWS), a tropical dry forest in Myanmar (Burma). CWS is one of the largest protected patches of tropical dry forest in Southeast Asia and supports over half the remaining wild population of the endangered Eld’s deer. Between 1973 and 2005, 62% of forest was lost at an annual rate of 1.86% in the area, while forest loss inside CWS was only 16% (0.45% annually). Based on trends found during our study period, dry forests outside CWS would not persist beyond 2019, while forests inside CWS would persist for at least another 100 years. Analysis of temporal deforestation patterns indicates the highest rate of loss occurred between 1992 and 2001. Conversion to agriculture, shifting agriculture, and flooding from a hydro-electric development were the main deforestation drivers. Fragmentation was also severe, halving the area of suitable Eld’s deer habitat between 1973 and 2001, and increasing its isolation. CWS protection efforts were effective in reducing deforestation rates, although deforestation effects extended up to 2 km into the sanctuary. Establishing new protected areas for dry forests and finding ways to mitigate human impacts on existing forests are both needed to protect remaining dry forests and the species they support.     

Detecting Long-term Global Forest Change Using Continuous Fields of Tree-Cover Maps from 8-km Advanced Very High Resolution Radiometer (AVHRR) Data for the Years 1982–99

This paper describes global changes in forest cover from 1982 to 1999 based on the 8-km Pathfinder Advanced Very High Resolution Radiometer (AVHRR) data set. The procedure involves the use of a regression tree in predicting percent tree cover for the years 1982–99. Training data are created from high-resolution imagery and used with phenological metrics derived from the annual AVHRR time series. Using the 18 years of estimated tree cover, and based on a thresholding approach, we identified locations where change in tree cover has occurred. The change sites were then compared to a set of high-resolution deforestation analyses to yield area estimates of deforestation and regrowth. Percent tree cover was found to have decreased globally, from the 1980s to 1990s, in contrast to United Nations Food and Agriculture Organization (FAO) reports of a global increase in forest cover. Latin America and tropical Asia are the two dominant deforestation regions. Paraguay shows the highest rate of forest clearing over the time series, while Indonesia had the greatest increase in deforestation from the 1980s to 1990s. We also suggest that the percent tree-cover maps can be used in standardizing national forest statistics, as an objective means of identifying hot spots of change, and for facilitating ecosystem monitoring.     

Expanding temporal resolution in landscape transformations: Insights from a landsat-based case study in Southern Chile

Understanding temporal and spatial dimensions of land cover dynamics is a critical factor to link ecosystem transformation to land and environmental management. The trajectory of land cover change is not a simple difference between two conditions, but a continuous process. Therefore, there is a need to integrate multiple time periods to identify slow and rapid transformations over time. We mapped land cover composition and configuration changes using time series of Landsat TM/ETM+ images (1985–2011) in Southern Chile to understand the transformation process of a temperate rainforest relict and biodiversity hotspot. Our analysis builds on 28 Landsat scenes from 1985 to 2011 that have been classified using a random forests approach. Base on the high temporal data set we quantify land cover change and fragmentation indices to fully understand landscape transformation in this area. Our results show a high deforestation process for old growth forest strongest at the beginning of the study period (1985–1986–1998–1999) followed by a progressive slowdown until 2011. Within different study periods deforestation rates were much larger than the average rate over the complete study period (0.65%), with the highest annual deforestation rate of 1.2% in 1998–1999. The deforestation resulted in a low connectivity between native forest patches. Old-growth forest was less fragmented, but was concentrated mainly in two large regions (the Andes and Coastal mountain range) with almost no connection in between. Secondary forest located in more intensively used areas was highly fragmented. Exotic forest plantation areas, one of the most important economic activities in the area, increased sevenfold (from 12,836 to 103,540 ha), especially during the first periods at the expense of shrubland, secondary forest, grassland/arable land and old grown forest. Our analysis underlines the importance of expanding temporal resolution in land cover/use change studies to guide sustainable ecosystem management strategies as increase landscape connectivity and integrate landscape planning to economic activities. The study is highlighting the key role of remote sensing in the sustainable management of human influenced ecosystems.     

Mangrove forest distributions and dynamics (1975–2005) of the tsunami‐affected region of Asia†

Aim We aimed to estimate the present extent of tsunami‐affected mangrove forests and determine the rates and causes of deforestation from 1975 to 2005. Location Our study region covers the tsunami‐affected coastal areas of Indonesia, Malaysia, Thailand, Burma (Myanmar), Bangladesh, India and Sri Lanka in Asia. Methods We interpreted time‐series Landsat data using a hybrid supervised and unsupervised classification approach. Landsat data were geometrically corrected to an accuracy of plus‐or‐minus half a pixel, an accuracy necessary for change analysis. Each image was normalized for solar irradiance by converting digital number values to the top‐of‐the atmosphere reflectance. Ground truth data and existing maps and data bases were used to select training samples and also for iterative labelling. We used a post‐classification change detection approach. Results were validated with the help of local experts and/or high‐resolution commercial satellite data. Results The region lost 12% of its mangrove forests from 1975 to 2005, to a present extent of c. 1,670,000 ha. Rates and causes of deforestation varied both spatially and temporally. Annual deforestation was highest in Burma (c. 1%) and lowest in Sri Lanka (0.1%). In contrast, mangrove forests in India and Bangladesh remained unchanged or gained a small percentage. Net deforestation peaked at 137,000 ha during 1990–2000, increasing from 97,000 ha during 1975–90, and declining to 14,000 ha during 2000–05. The major causes of deforestation were agricultural expansion (81%), aquaculture (12%) and urban development (2%). Main conclusions We assessed and monitored mangrove forests in the tsunami‐affected region of Asia using the historical archive of Landsat data. We also measured the rates of change and determined possible causes. The results of our study can be used to better understand the role of mangrove forests in saving lives and property from natural disasters such as the Indian Ocean tsunami, and to identify possible areas for conservation, restoration and rehabilitation.     

森林退化/衰退的研究与实践

森林退化可以理解为森林面积减少、结构丧失、质量降低、功能下降;森林衰退则是森林退化的一种形式,指森林（树木）在生长发育过程中出现的生理机能下降、生长发育滞缓、生产力降低甚至死亡,以及地力衰退等状态.国内外研究表明,森林采伐/毁林是造成森林面积减少的最主要原因,有关森林采伐/毁林引起的森林退化研究主要集中在森林退化的后果、国家/国际政策的影响、加强全球性合作以及寻求解决途径等方面.森林衰退原因可归纳为：工、农业污染,自然胁迫/致衰因子,林分动态发生变化,森林衰退病或生态病,人工纯林以及纯林连栽导致的地力、生产力衰退等.中国的森林退化/衰退现状与世界各地森林退化基本一致,但由于历史原因,中国森林退化又有其自身特点：近一个世纪的强烈人为干扰,使大部分原始天然林退化为次生林;中国拥有世界上最多的人工林,且多数人工林均具有质量差、功能低等衰退特征.本文在综述森林退化/衰退研究与实践基础上,提出中国现代森林退化/衰退的的主要原因,给出中国森林退化/衰退的基本对策.     

Assessing the effect of climate change on carbon sequestration in a Mexican dry forest in the Yucatan Peninsula

Assessing the effect of climate change on carbon sequestration in tropical forest ecosystems is important to inform monitoring, reporting, and verification (MRV) for reducing deforestation and forest degradation (REDD), and to effectively assess forest management options under climate change. Two process-based models, Forest-DNDC and Biome-BGC, with different spatial modeling scales were evaluated to estimate the potential effect of climate change on carbon sequestration in a tropical dry semi-deciduous forest in the Yucatan Peninsula of Mexico. The results from the simulations using the two models show that carbon sequestration in this dry forest is highly sensitive to warming. Carbon uptake in this forest may increase or decrease slightly with a corresponding increase or decrease in precipitation; however, with an increase in temperature, carbon uptake may decrease significantly, showing that warming may be the main climate factor that impacts carbon storage in this tropical dry forest. Model performance evaluation indicates that both models may be used to estimate C stocks, but DNDC may be better than BGC for assessing the effect of climate change on C dynamics.     

Validating Community-Led Forest Biomass Assessments

The lack of capacity to monitor forest carbon stocks in developing countries is undermining global efforts to reduce carbon emissions. Involving local people in monitoring forest carbon stocks could potentially address this capacity gap. This study conducts a complete expert remeasurement of community-led biomass inventories in remote tropical forests of Papua New Guinea. By fully remeasuring and isolating the effects of 4,481 field measurements, we demonstrate that programmes employing local people (non-experts) can produce forest monitoring data as reliable as those produced by scientists (experts). Overall, non-experts reported lower biomass estimates by an average of 9.1%, equivalent to 55.2 fewer tonnes of biomass ha^-1, which could have important financial implications for communities. However, there were no significant differences between forest biomass estimates of expert and non-expert, nor were there significant differences in some of the components used to calculate these estimates, such as tree diameter at breast height (DBH), tree counts and plot surface area, but were significant differences between tree heights. At the landscape level, the greatest biomass discrepancies resulted from height measurements (41%) and, unexpectedly, a few large missing trees contributing to a third of the overall discrepancies. We show that 85% of the biomass discrepancies at the tree level were caused by measurement taken on large trees (DBH ≥50cm), even though they consisted of only 14% of the stems. We demonstrate that programmes that engage local people can provide high-quality forest carbon data that could help overcome barriers to reducing forest carbon emissions in developing countries. Nonetheless, community-based monitoring programmes should prioritise reducing errors in the field that lead to the most important discrepancies, notably; overcoming challenges to accurately measure large trees.