Loss Of Cover Research Articles

Analysing patterns of forest cover change and related land uses in the Tano-Offin forest reserve in Ghana: Implications for forest policy and land management

Forest cover change is a major contributing factor to global environmental change. Whereas several studies have focused on the general land use and land cover dynamics, we focus on analysing forest cover change patterns in a protected landscape taking into consideration how other land categories are increasing at the expense of the forest. In this study, we analyse forest cover change patterns and associated proximate land use factors between 1987 and 2017 using Landsat images from the Tano-Offin Forest Reserve (TOFR) in Ghana. Using the Random Forest machine learning algorithm, we classified the images into forest, developed land, and agricultural land. The study finds that forest cover losses are 1.9 and 1.4 times the amount of forest cover gains in 1987–2002 and 2002–2017, respectively. We find that even though the forest cover is more likely to recover from the agricultural land, land developers mostly targeted the agricultural land. The focus of Ghana's Forest and Wildlife Policy and the underlying process of forest cover change in the TOFR suggest that a country's forest policy should focus on a combination of diverse and spatially explicit proximate factors that are likely to threaten the integrity of forests.

Assessing the tropical forest cover change in northern parts of Sonitpur and Udalguri District of Assam, India

Sonitpur and Udalguri district of Assam possess rich tropical forests with equally important faunal species. The Nameri National Park, Sonai-Rupai Wildlife Sanctuary, and other Reserved Forests are areas of attraction for tourists and wildlife lovers. However, these protected areas are reportedly facing the problem of encroachment and large-scale deforestation. Therefore, this study attempts to estimate the forest cover change in the area through integrating the remotely sensed data of 1990, 2000, 2010, and 2020 with the Geographic Information System. The Maximum Likelihood algorithm-based supervised classification shows acceptable agreement between the classified image and the ground truth data with an overall accuracy of about 96% and a Kappa coefficient of 0.95. The results reveal a forest cover loss of 7.47% from 1990 to 2000 and 7.11% from 2000 to 2010. However, there was a slight gain of 2.34% in forest cover from 2010 to 2020. The net change of forest to non-forest was 195.17 km2 in the last forty years. The forest transition map shows a declining trend of forest remained forest till 2010 and a slight increase after that. There was a considerable decline in the forest to non-forest (11.94% to 3.50%) from 2000–2010 to 2010–2020. Further, a perceptible gain was also observed in the non-forest to the forest during the last four decades. The overlay analysis of forest cover maps show an area of 460.76 km2 (28.89%) as forest (unchanged), 764.21 km2 (47.91%) as non-forest (unchanged), 282.67 km2 (17.72%) as deforestation and 87.50 km2 (5.48%) as afforestation. The study found hotspots of deforestation in the closest areas of National Park, Wildlife Sanctuary, and Reserved Forests due to encroachments for human habitation, agriculture, and timber/fuelwood extractions. Therefore, the study suggests an early declaration of these protected areas as Eco-Sensitive Zone to control the increasing trends of deforestation.

Historical evolution and future trend of Northern Hemisphere snow cover in CMIP5 and CMIP6 models

Historical snow cover over the Northern Hemisphere was examined in the satellite-based NOAA-CDR data for the period of 1970–2019. Observed annual snow cover fraction (SNF) has reduced over most areas by up to 2%/decade, while annual snow cover area (SCA) has reduced by 2 × 105 km2/decade. However, SCA in the October–December season has increased by about 5 × 105 km2/decade. CMIP5 and CMIP6 historical experiments were validated against the NOAA-CDR data. Snow cover was generally well simulated in both CMIPs, with CMIP6 models performing better. The biases in SCA reduction were larger and smaller during summer and winter, respectively. The observed increase of October–November–December SCA in the 2000s was not reproduced. Climate projections of future snow cover were evaluated in CMIP6. SNF is projected to decrease in the next 80 years, under all four scenarios evaluated (SSP126, SSP245, SSP370 and SSP585). The higher the greenhouse emissions in the shared socio-economic pathways, the faster the reduction. Under the SSP585 scenario, the rate of SCA reduction is projected to exceed −1.2 × 106 km2/decade. By 2081–2100, annual (January–March) SCA is projected to decrease by more than 30% (20%). Under the SSP126 scenario, annual (January–March) SCA is projected to only reduce by about 10% (5%) relative 1995–2014 values. The reduction of Greenhouse gas emissions is critical to controlling the loss of snow cover; future snow cover only stabilizes under the SSP126 scenario, but continue to decrease under the other three scenarios.

Landscape effects on taxonomic and functional diversity of dung beetle assemblages in a highly fragmented tropical forest

We evaluated how the taxonomic and functional diversity of dung beetles responds to landscape fragmentation in Los Tuxtlas Biosphere Reserve (LTBR). We sampled dung beetle assemblages in 15 landscapes (spatial windows) representing a gradient of forest cover loss and evaluated the degree of forest fragmentation in each landscape. The percentage of forest coverage of each landscape had a significant positive effect on species richness (0D), Shannon diversity (1D), and functional divergence of dung beetles. Forest fragmentation was negatively related to Simpson diversity (2D), biomass, and functional evenness of dung beetles, whereas their functional richness expanded as forest fragmentation increased. Taxonomic and functional beta diversity were positively correlated; the former was driven mainly by species replacement and the latter by nestedness. Functional alpha and beta diversities varied mostly at random, as did the probability of co-occurrence between species. However, the few non-random positive associations between species involved small-bodied forest dung beetles. Species and their ecological traits are lost randomly in the landscape, suggesting a surprising resilience of dung beetle assemblages to forest cover loss. Nevertheless, loss and fragmentation of forest coverage had an unbalancing effect on dung beetle abundance and trait distribution, reducing their functional evenness, and divergence while favoring the establishment of small-sized species. In conclusion, although the LTBR has buffered further loss of dung beetle species and functional richness, it cannot effectively safeguard all aspects of their functional diversity. Our results suggest that the recovery of the original forest cover and large mammals is crucial for maintaining the taxonomic and functional diversity of dung beetles in tropical rainforests.

A three decade assessment of forest cover changes in Nijhum dwip national park using remote sensing and GIS

Forest cover loss has a crucial impact on global climate change. The Nijhum Dwip National Park (NDNP), a deltaic part of the Sundarbans mangrove forest, has changed significantly over the decades. The goal of this study was to detect the decadal changes in forest cover using freely available satellite remote sensing data and GIS tools. A maximum likelihood classification technique was used to classify the Landsat images of 1990, 2001, 2011 and 2020. The potential of NDVI and SAVI-based classification for detection of forest cover changes in comparison to supervised classification was also evaluated. More than 42% of the total forest cover area (1781 ha) has been deforested over the decades between 1990 and 2011. The study also reported that nearly 1235 ha and over 856 ha of forest area disappeared from 4217.5 ha in 1990 to 2982.5 ha and 2126.16 ha in 2001 and 2011, respectively. In contrast, an increase of 310 ha of forest area has been recorded in the last decade, from 2011 to 2020. NDVI performed better in forest cover change detection than SAVI. This research will be invaluable for this type of research continuity and proper monitoring of this protected mangrove forest area, along with providing useful information to decision makers.

Predicting bird species presence in urban areas with NDVI: An assessment within and between cities

The increasing urbanization within cities correlates with the loss of green cover, affecting the distribution of bird species. Therefore, to foresee possible effects induced by green cover loss, it is essential to have spatial data of species occurrence. Remote sensors produce spatial data of green cover, such as the Normalized Difference Vegetation Index (NDVI), which can be used to model bird species occurrence within and between cities. The objectives of this study were: 1) to construct and evaluate predictive models between NDVI and bird species distribution in Mar del Plata city, Argentina; and 2) to extrapolate these models to two other cities of the region, Balcarce and Miramar. Most of the 21 species analyzed showed positive associations with NDVI. However, the minimum NDVI values at which species started to be present were dissimilar, showing different habitat requirements. The models of nine species had r-squared values ≥ 0.40, and eight of these species showed an adequate prediction of occurrence in additional areas of Mar del Plata. However, only the occurrence of the Tropical Kingbird (Tyrannus melancholicus) was adequately extrapolated to Miramar and Balcarce. Results showed that NDVI is successful to predict bird species occurrence within a city, but the extrapolation to other cities is not totally adequate. Thus, bird-habitat suitabilities for urban species are considered to be specific for each city.

Growing mining contribution to Colombian deforestation

Tropical deforestation is mainly driven by agricultural expansion, land grabbing, illegal logging, urbanization, cattle ranching as well as mining. However, extraction of minerals and its impacts in high biodiversity regions are still poorly known, particularly in Colombia, a tropical megadiverse hotspot. Here, using high-resolution datasets of forest cover changes and detailed geospatial mining data for Colombia, we show a growing contribution of legal mining to national deforestation: 3.4% over the 2001–2018 period, with a peak at 5.6% in 2017. During this period, around 121 819 ha have been deforested inside legal mining concessions, and an estimation of over 400 000 ha deforested by both legal and illegal. Gold and coal are the most important legally-mined materials in Colombia associated to deforestation, particularly in the recent years with 511% and 257% tree cover loss increases respectively (average over 2016–2018 compared to 2001–2015 average of mined material deforestation average). Three Colombian departments summed out ∼70% of the national deforestation occurring in legal concessions: in 2018, up to 23% of deforestation in Antioquia was taking place in legal mines (gold producer). Finally, we found that only 1% (respectively, 3%) of the concessions contribute to 60% (>90%) of the legal mining-related deforestation, mainly driven by large clearings to agriculture. Environmental law enforcement, monitoring activities and engaging the mining industry in effective forest conservation and landscape restoration strategies are urgently needed in Colombia for preserving biodiversity and ecosystem services.

The impact of deforestation on rainfall in Africa: a data-driven assessment

Forests play an important role in maintaining rainfall patterns worldwide by recycling water back to the atmosphere through evapotranspiration. We present a novel spatiotemporal data-driven model and assessment of the impacts of various deforestation scenarios on rainfall patterns in sub-Saharan Africa, where rainfed agriculture is the main source of income and provides food for a large part of the population. Our model is based on the convolutional long short term memory neural network and uses a combination of climate and vegetation time-series data to predict rainfall and to perform simulation experiments. Our results show that complete deforestation (i.e. conversion of all humid forests to short grasslands) would greatly reduce rainfall magnitude in the deforested areas. Above the equator, the large majority of areas not currently forested would also receive less rainfall. However, complete deforestation would slightly increase rainfall in some parts of Southern Africa and decrease it in other parts. The impacts of partial deforestation also differ across Africa. In West Africa, even moderate tree cover loss (i.e. 30%) reduces rainfall magnitude whereas in Central and Southern Africa, a threshold of 70% tree cover loss is required to reduce rainfall magnitude. Deforestation of remaining humid rainforest areas is thus likely to dramatically affect rainfed agriculture across the continent, in particular in the maize-based cropping systems north of the equator.

A survey of small mammals in the Volta Region of Ghana with comments on zoogeography and conservation

We examined small mammal (insectivores, bats and rodents) diversity in community and legally protected forest remnants in the Ghana-Togo Highlands of the Volta Region of Ghana, West Africa, a zoologically understudied area compared to neighboring Togo to the East, or Ghana west of the Volta River. We recorded 34 small mammal species: three species of shrews (Soricidae Fischer, 1815), 12 species of rodents, one primate (Galagidae Gray, 1825) and 17 species of bats (Chiroptera Blumenbach, 1779). The rodent Stochomys longicaudatus (Tullberg, 1893) appears to be a first record for Ghana. Two shrew, three rodent and one bat species were first records for the Volta Region. By comparing our small mammal captures and limited microhabitat data from 1999 and 2001 to forest cover change maps for the period 2000-2015 we discuss trends in species community changes due to forest cover loss and other disturbance regimes. Aside from contributing to our understanding of the distribution of several small mammal species, the study demonstrates the progressive loss of forest habitat in the Volta Region.

Stabilisation wedges: measuring progress towards transforming the global energy and land use systems

Fifteen years ago, Pacala and Socolow argued that global carbon emissions could be stabilised by mid-century using a portfolio of existing mitigation strategies. We assess historic progress for each of their proposed mitigation strategies and convert this into the unit of ‘wedges’. We show that the world is on track to achieve 1.5 ± 0.9 wedges relative to seven required to stabilise emissions, or 14 required to achieve net-zero emissions by mid-century. Substantial progress has been made in some domains that are not widely recognised (improving vehicle efficiency and declining vehicle use); yet this is tempered by negligible or even negative progress in many others (particularly tropical tree cover loss in Asia and Africa). By representing global decarbonisation efforts using the conceptually simple unit of wedges, this study helps a broader audience to understand progress to date and engage with the need for much greater effort over the coming decades.

The resilience of Amazon tree cover to past and present drying

The Amazon forest is increasingly vulnerable to dieback and encroachment of grasslands and agricultural fields. Threats to these forested ecosystems include drying, deforestation, and fire, but feedbacks among these make it difficult to determine their relative importance. Here, we reconstruct the central and western Amazon tree cover response to aridity and fire in the mid-Holocene—a time of less intensive human land use and markedly drier conditions than today—to assess the resilience of tree cover to drying and the strength of vegetation-climate feedbacks. We use pollen, charcoal, and speleothem oxygen isotope proxy data to show that Amazon tree cover in the mid-Holocene was resilient to drying in excess of the driest bias-corrected future precipitation projections. Experiments with a dynamic global vegetation model (LPJ-GUESS) suggest tree cover resilience may be owed to weak feedbacks that act to amplify tree cover loss with drying. We also compare these results to observational data and find that, under limited human interference, modern tree cover is likely similarly resilient to mid-Holocene levels of aridification. Our results suggest human-driven fire and deforestation likely pose a greater threat to the future of Amazon ecosystems than drying alone.

Seed-rain-successional feedbacks in wet tropical forests.

Tropical forest regeneration after abandonment of former agricultural land depends critically on the input of tree seeds, yet seed dispersal is increasingly disrupted in contemporary human-modified landscapes. Here, we introduce the concept of seed-rain-successional feedbacks as a deterministic process in which seed rain is shaped by successional dynamics internal to a forest site and that acts to reinforce priority effects. We used a combination of time series and chronosequence approaches to investigate how the quantity and taxonomic and functional composition of seed rain change during succession and to evaluate the strength of seed-rain-successional feedbacks, relative to other deterministic and stochastic mechanisms, in secondary wet forests of Costa Rica. We found that both successional niches and seed-rain-successional feedbacks shaped successional trajectories in the seed rain. Determinism due to successional niche assembly was supported by the increasing convergence of community structure to that of a mature forest, in terms of both functional and taxonomic composition. With successional age, the proportions of large-seeded, shade-tolerant species in the seed rain increased, whereas the proportion of animal-dispersed species did not change significantly. Seed-rain-successional feedbacks increased in strength with successional age, as the proportion of immigrant seeds (species not locally represented in the site) decreased with successional age, and the composition of the seed rain became more similar to that of the adult trees at the forest site. The deterministic assembly generated by seed-rain-successional feedback likely contributed to the increasing divergence of secondary forest sites from each other during succession. To the extent that human modification of tropical forest landscapes reduces connectivity via factors such as forest cover loss, our results suggest that seed-rain-successional feedbacks are likely to increasingly shape regeneration trajectories in and amplify floristic heterogeneity among tropical secondary forests.

Increasing coral calcification in Orbicella faveolata and Pseudodiploria strigosa at Flower Garden Banks, Gulf of Mexico

Coral reefs are globally in decline and western Atlantic reefs have experienced the greatest losses in live coral cover of any region. The Flower Garden Banks (FGB) in the Gulf of Mexico are high-latitude, remote reefs that are an outlier to this trend, as they have maintained coral cover ≥ 50% since at least 1989. Quantifying the long-term trends in coral growth of key reef-building coral species, and the underlying environmental drivers, leads to a better understanding of local sensitivities to past changes that will ultimately allow us to better predict the future of reef growth at FGB. We obtained coral cores and constructed growth records for two of the most abundant hermatypic coral species at FGB, Pseudodiploria strigosa and Orbicella faveolata. Our records cover 57 yrs of growth for P. strigosa (1957–2013) and 45 yrs for O. faveolata (1970–2014). Linear extension and calcification rates of both species have increased significantly, but skeletal density did not change over the respective time periods. Extension and calcification data of both species combined were negatively correlated with the discharge from the Atchafalaya River, but positively correlated with maximum sea surface temperatures (SST). These data provide evidence that runoff from the Atchafalaya River impacts FGB corals and is a major control on coral growth at FGB. The increase in growth at FGB can be attributed to the significant warming trend in maximum monthly SSTs. Given the warming trend and recent increase in severity of bleaching at FGB, the prognosis is that bleaching events will become more deleterious with time, which will lead to a breakdown in the positive relationship between coral growth and maximum SST. This study provides further evidence that some high-latitude, cooler reef sites have experienced a stimulation in coral growth with ocean warming.

Built-up area expansion in the Wa Municipality of Ghana: implications for vegetation cover loss and fragmentation

ABSTRACT This study draws on the patch-mosaic model and uses geospatial and statistical methods to assess vegetation fragmentation specifically from built-up area expansion between 1990 and 2018 in the Wa Municipality of Ghana. The study finds that 0.19% and 0.33% annual expansion in the built-up area from 1990-2006 and 2006-2018 contributed to annual vegetation patch size variability (coefficient of variation in the patch size) of 1.82% and 120.97% from 1990-2006 and 2006-2018, respectively. Our results suggest that a higher rate of increase in built-up area would likely create larger quantities of intermixed vegetation and built-up patches.

State of the Landscape and Dynamics of Loss and Fragmentation of Forest Critically Endangered in the Tropical Andes Hotspot: Implications for Conservation Planning

Abstract Currently, there is no precise information on the degree of transformation of Tropical Andes hotspot landscape and native ecosystems due to the intensification of agricultural and urban land-use. Proper knowledge of these changes would provide crucial information for planning conservation strategies. We evaluated the impact of the intensification of agricultural and urban land-use on the Inter-Andean Dry Forest and Tropical Montane Forest, both of which are categorized as Critically Endangered, and the state of the landscape in the High Rio Guayllabamba watershed, Ecuador, during the periods 1991–2005 and 2005–2017. The evaluation was carried out using Landsat satellite images of 30 x 30 m pixels and landscape metrics. We found an advanced state of landscape transformation. Since the 1990s, the loss of both ecosystems was largely caused by the conversion of forest to agriculture, resulting in substantial changes in the spatial configuration of these ecosystems. From 1991 to 2017, 19.8 % and 16.1 % of Inter-Andean Dry Forest and Tropical Montane Forest respectively, were converted to agriculture. The loss of Inter-Andean Dry Forest was 28 % and the number of forest patches increased by more than 150%. The loss of Tropical Montane Forest was 16.5 % and the number of forest patches increased by more than 300 %. The largest loss and fragmentation of forest cover occurred from 1991 to 2005. We suggested planning landscape-scale conservation, using the patch-corridor-matrix model. This model is appropriate given the current configuration of the landscape studied, with Inter-Andean Dry Forest and Tropical Montane Forest restricted to small patches sparsely distributed across the landscape.

Develop of Local Flat Plate Solar Heater

A new system of local flat plate solar water heater “LPSH” recommended to be used for heating water as step for maximizing renewable source of energy instead of traditional power.The local flat plate solar water heater is used to heat water from the atmospheric temperature. Evacuated, double and single glasses flat plate solar water heater were fabricate with the same dimensions and installed at a latitude angle of 31 degree facing towards N-S direction.The experiment has been carried out at 24th March 2021 between 8.00 AM to 5.00 PM.The solar collector efficiency depends with many parameters such as type of glass cover, wind velocity and overall top loss heat transfer coefficient.Top loss heat transfer coefficient (Ut) plays an important role for design of solar collector.Taking this point under consideration the present work is to reduce the overall top loss heat transfer coefficient and improve the collector efficiency.The result shows that the efficiency of (LVDG) is higher compared to (LDG) and (LSG).The higher instantaneous and collector efficiency of (LVDG) obtain as a result of the overall top loss heat transfer coefficient (Ut) was reduced in (LVDG). The efficiency of (LVDG), (LDG) and (LSG) achieve around 79, 68 and 45 %, caused by the high heat increase at 12:00 pm.The efficiency decreased for (LSG) as a result of the high top loss heat transfer coefficient. The maximum overall top loss heat transfer coefficient Ut was recorded (2.51, 3.77, and 6.35 W/ m2 K) for (LVDG), (LDG) and (LSG) at 12:00 pm, respectively.

The Implication of Land Use Land Cover Change on Biodiversity Conservation: An Overview from Protected Areas in Ethiopia

Conversion of natural habitat to other forms of land use is the main threat to protected areas and biodiversity globally. The continued trend of land use land cover change in protected areas resulted in loss of a large portion of biodiversity, overexploitation by humans, transformation of natural land to human settlement, etc. In Ethiopia, the causes for land use land cover change in many protected areas are farmland expansion, deforestation, unsustainable grazing and settlement expansion, and are leading to loss of biodiversity and negative impacts of ecosystem services. In addition, Ethiopia’s protected areas entertain escalating threats and land cover changes due to human population growth, competing claims from the surrounding communities, incompatible investment, lack of environmental law enforcement, absence of complete plan and timely update for protected areas, etc. These have affected protected areas in the country namely the Bale Mountains National Park, Chocke Mountains, Babile Elephant sanctuary, Abijata Shalla Lakes National Park, Awash National Park and others. The continued land use land cover changes are aggravating ecosystem, soil and water resources degradation in mountainous protected areas while they are leading to biodiversity destruction and loss of forest cover in lowland protected areas. In order to halt and reduce the impact of land cover change on biodiversity conservation, undertaking complete land use planning and continuous monitoring of protected areas was found to be important. Similarly, integrating protected areas into the surrounding landscapes and a broader framework of national plans, promoting income generation means for communities surrounding protected areas, promoting biodiversity conservation directly linked to poverty alleviation, involving local communities and stakeholders in land use planning and sustainable management of protected areas, enhancing sound management in vulnerable mountain protected areas and restoring abandoned lands located in and around protected areas are crucial in the proper land use planning and management of protected areas. In addition, enhancing awareness creation and promoting natural resource information of protected areas and enhancing scientific study on land use land cover change pattern of protected areas are vital to undertake effective land use planning and management of protected areas in Ethiopia.

Limited protection and ongoing loss of tropical cloud forest biodiversity and ecosystems worldwide.

Tropical cloud forests (TCFs) are one of the world's most species- and endemism-rich terrestrial ecosystems. TCFs are threatened by direct human pressures and climate change, yet the fate of these extraordinary ecosystems remains insufficiently quantified. With discussions of the post-2020 biodiversity framework underway, TCFs are a defining test case of the success and promise of recent policy targets and their associated mechanisms to avert the global biodiversity crisis. Here we present a global assessment of the recent status and trends of TCFs and their biodiversity and evaluate the efficacy of current protection measures. We find that cloud forests occupied 0.4% of the global land surface in 2001 and harboured ~3,700 species of birds, mammal, amphibians and tree ferns (~15% of the global diversity of those groups), with half of those species entirely restricted to cloud forests. Worldwide, ~2.4% of cloud forests (in some regions, more than 8%) were lost between 2001 and 2018, especially in readily accessible places. While protected areas have slowed this decline, a large proportion of loss in TCF cover is still occurring despite formal protection. Increased conservation efforts are needed to avert the impending regional or global demise of TCFs and their unique biodiversity.

Offsite effects of mining on the frequency and abundance of five understorey plant species in western Québec (Canada)

Although the mining industry provides minerals and metals to the global market and represents important economic opportunities, it also constitutes a major anthropogenic disturbance in the ecosystems where it takes place. However, little is known about its offsite impacts on plant communities. We assessed the frequency and the abundance of five common boreal understorey plant species (Coptis trifolia (L.) Salisb., Cornus canadensis L., Linnaea borealis L., Lysimachia borealis (Raf.) U.Manns & Anderb., and Maianthemum canadense Desf.) at different distances around six mines in Abitibi-Témiscamingue and Nord-du-Québec (Québec). Frequency and (or) abundance of Coptis trifolia and M. canadense decreased near mines, suggesting that they might be sensitive to the loss of forest cover, particle deposition, and soil contamination induced by mining. Conversely, the frequency and abundance of Cornus canadensis increased near active mines, which indicates its resilience to the stress caused by mines and its ability to exploit the niche space left by more sensitive species. No effects on Linnaea borealis and Lysimachia borealis were observed. Our study suggests the possible presence of offsite impacts of mines on plant communities. Further studies considering enigmatic impacts should be conducted in order to develop our understanding of the broader environmental footprint of mining activity.

Detecting and predicting forest degradation: A comparison of ground surveys and remote sensing in Tanzanian forests

Societal Impact StatementLarge areas of tropical forest are degraded. While global tree cover is being mapped with increasing accuracy from space, much less is known about the quality of that tree cover. Here we present a field protocol for rapid assessments of forest condition. Using extensive field data from Tanzania, we show that a focus on remotely‐sensed deforestation would not detect significant reductions in forest quality. Radar‐based remote sensing of degradation had good agreement with the ground data, but the ground surveys provided more insights into the nature and drivers of degradation. We recommend the combined use of rapid field assessments and remote sensing to provide an early warning, and to allow timely and appropriately targeted conservation and policy responses.Summary Tropical forest degradation is widely recognised as a driver of biodiversity loss and a major source of carbon emissions. However, in contrast to deforestation, more gradual changes from degradation are challenging to detect, quantify and monitor. Here, we present a field protocol for rapid, area‐standardised quantifications of forest condition, which can also be implemented by non‐specialists. Using the example of threatened high‐biodiversity forests in Tanzania, we analyse and predict degradation based on this method. We also compare the field data to optical and radar remote‐sensing datasets, thereby conducting a large‐scale, independent test of the ability of these products to map degradation in East Africa from space. Our field data consist of 551 ‘degradation’ transects collected between 1996 and 2010, covering >600 ha across 86 forests in the Eastern Arc Mountains and coastal forests. Degradation was widespread, with over one‐third of the study forests—mostly protected areas—having more than 10% of their trees cut. Commonly used optical remote‐sensing maps of complete tree cover loss only detected severe impacts (≥25% of trees cut), that is, a focus on remotely‐sensed deforestation would have significantly underestimated carbon emissions and declines in forest quality. Radar‐based maps detected even low impacts (<5% of trees cut) in ~90% of cases. The field data additionally differentiated types and drivers of harvesting, with spatial patterns suggesting that logging and charcoal production were mainly driven by demand from major cities. Rapid degradation surveys and radar remote sensing can provide an early warning and guide appropriate conservation and policy responses. This is particularly important in areas where forest degradation is more widespread than deforestation, such as in eastern and southern Africa.