Regional Forest Cover Research Articles

How does the value of ecological restoration techniques affect ecosystem carbon density: A resource endowment-based perspective

In the context of carbon neutrality and carbon peaks, innovations in ecological restoration technology play a key role in carbon adsorption and maintaining ecological balance. Regional governments, tasked with formulating differentiated and rational ecologically sustainable development plans and carbon-neutral strategies tailored to various resource endowment conditions, require timely identification of the mechanisms by which ecological restoration technologies affect the carbon density of ecosystems. Based on data from 31 provinces in China from 2006 to 2021, this study employed the Spatial Durbin Model with both time and space fixed effects to examine the impact of the value of ecological restoration technologies on ecosystem carbon density under varying resource endowments. The empirical results indicate that (1) the value of ecological restoration technology has a significantly positive effect on ecosystem carbon density, particularly in neighbouring areas; (2) energy resource endowment exhibits a significantly inverted U-shaped boundary effect, whereby regions with moderate energy endowment can optimise the positive impact of ecological restoration technology; (3) the heterogeneity analysis, based on levels of regional environmental governance and forest cover, shows that in regions with less investment in environmental infrastructure and lower forest cover, ecosystem carbon density is more sensitive to the value of ecological restoration techniques, making their carbon sink effect more pronounced. This study elucidates the key role of ecological restoration techniques in enhancing carbon storage, promoting the goal of carbon neutrality, and identifying optimal pathways for increasing ecosystem carbon stocks across various regions with differing resource endowments. Moreover, it provides a reference for accelerating the achievement of carbon neutrality targets.

Links between deforestation, conservation areas and conservation funding in major deforestation regions of South America

Abstract Land‐use change is a major driver of biodiversity loss, affecting tropical forests and savannas at an unprecedented rate. To protect these ecosystems and their biodiversity, national conservation areas and international conservation funding have increased considerably in these regions. Understanding of how conservation funding allocation relates to dynamics in deforestation and conservation areas is crucial to identifying what mobilizes and distributes conservation funding. By applying fixed‐effect models on 30 years of dynamics in forest cover, conservation areas and conservation funding in the main deforestation regions of South America, we analysed the conservation funding allocation strategies in relation to deforestation (proactive vs. reactive), conservation areas (expanding or consolidating) and previous investment (agglomerating or not). We also assessed whether allocation strategies vary across regions and the stages of deforestation and conservation. We found that funding allocation followed conservation areas and higher prior funding levels over space and over time, across all regions and deforestation stages. This highlights the important role of recognized conservation areas (including protected areas and Indigenous territories) in mobilizing financial support for conservation. The allocation strategies relating to forest dynamics, however, varied depending on the scale of analysis, whether we look at the temporal or spatial dimension, and in which regions we assessed the allocation patterns. Capturing region‐level biases and within‐region dynamics is crucial for more effective and equitable conservation. As public and private actors commit to mobilizing more conservation funding and conserving more areas of the Earth, our insights on the relations between forest change and conservation efforts can help improve the allocation of conservation areas and conservation funding. Read the free Plain Language Summary for this article on the Journal blog.

Effect of local habitat and landscape attributes on bird communities in shade coffee plantations in the Colombian Andes

Agroforestry is increasingly promoted to support biodiversity conservation by increasing tree cover in agricultural landscapes, but the extent to which landscape context affects how benefits accrue remains uncertain. We used shade-coffee systems to ask how the proximity and extent of forest and forest-agriculture mosaic in the landscape influenced bird communities in 160 coffee plantations that differed in coffee plant density and shade tree richness and abundance in two departments of Colombia with differing regional forest cover. Our findings suggest that regional forest cover and landscape conditions can mediate the response of birds to local habitats on plantations. Avian richness and community completeness was positively related to the amount of forest-agriculture mosaic within landscapes surrounding coffee plantations only within the comparatively forested department of Antioquia (mean 32 % regional forest cover), particularly where plantations had high richness and abundance of trees. In the largely deforested department of Cauca (mean 1 %), neither distance to forest nor cover by forest-agriculture mosaics explained avian richness and community completeness, both of which were positively related only to local tree richness and abundance. We show that biodiversity benefits from increasing habitat quality at local and landscape scales, and habitat quality within plantations becomes increasingly influential as the amount of habitat in the broader landscape declines. Our results emphasize the role of landscape context in conservation planning to promote biodiversity in coffee-growing regions.

Landsat-observed changes in forest cover and attribution analysis over Northern China from 1996‒2020

ABSTRACT Forest dynamics provide important information on the ecological environment. The Three-North Shelter Forest Program (TNSFP) is one of the world’s largest reforestation/afforestation programs, however the actual changes in forest cover in the Three-North Regions (TNR) of China resulting from this program are highly uncertain. This study quantified changes in fractional forest cover (FFC) at 30 m using Landsat data from 1996 to 2020. Using the Google Earth Engine platform, more than 40,000 images from Landsat-5, Landsat 7 and Landsat-8 were integrated, and the annual surface reflectance was normalized based on the multi-band least squares regression and maximum normalized difference vegetation index composite method. An ensemble learning model trained using high-resolution Gao-Fen 2 satellite imagery was used to generate the FFC long time-series product. FFC showed an increasing trend with average rates of 0.022/10a in the last 25 years, and 0.03/10a after 2010 largely corresponding to the fourth and fifth phases of the TNSFP. There are significant regional differences in the relationship between FFC and air temperature ( R 2 = 0.37) and precipitation ( R 2 = 0.49). The increased air temperature in arid and less rainy areas inhibit the FFC increase, whereas the increase in precipitation had a promoting effect. FFC appeared more sensitive to changes in solar radiation and heat conditions in humid and rainy areas. The attribution analysis revealed that 34% of FFC changes were caused by climatic variables and 66% were caused by non-climatic factors. Among them, afforestation associated with the TNSFP significantly increased FFC, and forest fire is a key factor of forest change in the Greater Khingan Ranges and Lesser Khingan Ranges regions. Planting single tree species caused biological disasters in forests of Xinjiang and Inner Mongolia. Further analysis of the increased FFC using high-level satellite products demonstrated an improvement in environmental conditions with cooler land surface temperature and higher vegetation gross primary production over the TNR.

Climate and sea-level fluctuations on the western coast of Bohai Bay during the 4.2 ka event: Multi-proxy evidence from the Nandagang area of Cangzhou, China

The 4.2 ka event was an important climatic event during the mid–late Holocene, with significant effects on the ecological environment and climatic evolution of different regions. Coastal wetlands, as a transitional ecosystem between land and sea, are sensitive to changes in climate and sea level; hence, research on coastal wetlands is important for reconstructing past climate and sea-level changes and for predicting future changes. However, little research has been conducted on the characteristics of the 4.2 ka event on the western coast of Bohai Bay in China. We analyzed the pollen assemblages (214 samples), grain size, and geochemical element contents of a mid–late Holocene sedimentary sequence from the Nandagang (NDG) wetland on Bohai Bay, with the chronology based on 13 AMS 14C dates. The results revealed the history of climate and sea-level changes on the western coast of Bohai Bay during the interval of 5000–3600 cal yr BP. High sedimentary arboreal pollen concentrations indicated that the NDG area had a relatively dense cover and humid climate during 5000–4450 cal yr BP. During the 380-year interval of 4450–4070 cal yr BP, corresponding to the 4.2 ka event, the decreased representation of arboreal pollen indicated a decrease in the regional forest cover and an arid climate. The internal structure of the 4.2 ka event recorded in core NDG showed a dry-wet-dry temporal structure during the intervals of 4450–4290 cal yr BP, 4290–4170 cal yr BP, and 4170–4070 cal yr BP, respectively, together with a relatively low sea level. Comparison of the relative sea level (RSL) record of the NDG wetland with similar records from other coastal regions in East Asia during the 4.2 ka event revealed contrasting trends. During 4070–3600 cal yr BP, the tree pollen concentration increased again, indicating that the forest vegetation coverage increased and the climate became wetter. Overall, our results suggest that the 4.2 ka event, as recorded in Bohai Bay, was related to the reduced influence of the western Pacific Ocean Warm Pool and the more frequent occurrence of the El Niño–Southern Oscillation.

Reconstructing valley landscapes. GIS-analyses of past land use changes in three Flemish river valleys since the late 18th century

The restoration of riverine ecosystem services and floodplain landscapes has become an important tool in climate mitigation, however, it is often unclear what landscape a restoration is (or should be) referring to. Little is known moreover, about long-term transitions in historic valley land use or how they echo in contemporary perceptions of floodplain landscapes. Also in densely populated Flanders (in the north of Belgium), where floodplains are quickly losing their natural functions, policymakers are actively in pursuit of climate change adaptation strategies and sustainable valley management. We present the results of a GIS-based reconstruction of historical land use in three Flemish river valleys from 1771 to 2002 and compare them to changes in regional land use. We find that while grasslands initially and to a vast extent covered our selected floodplains, the latter were by the mid-19th century cultivated for agricultural production, in line with a global expansion of arable land and regional demographic growth. Also forest cover in the studied river valleys grew exponentially from the late 19th century, unmatched by regional forest cover. After the Second World War, a denser road network, more area that is built-up and forest plantations visually contributed to valley compartmentalisation and the perception of a closed landscape. Varying soil textures and drainage levels or the (in)ability to manage them properly accounted for different(ly) (timed) land use changes between the studied floodplain areas. Regional changes in historic land use were of lesser importance.

Holocene forest and land-use history of the Erzgebirge, central Europe: a review of palynological data

Abstract. The ongoing ecological conversion of mountain forests in central Europe from widespread Picea monocultures to mixed stands conceptually also requires a historical perspective on the very long-term, i.e. Holocene, vegetation and land-use dynamics. Detailed sources of information for this are palynological data. The Erzgebirge in focus here, with a maximum height of 1244 m a.s.l., represents an extreme case of extensive historical deforestation since the Middle Ages due to mining, metallurgy, and other industrial activities, as well as rural and urban colonisation. For this regional review we collected and evaluated 121 pollen diagrams of different stratigraphic, taxonomic, and chronological resolution. This number makes this region an upland area in central Europe with an exceptionally high density of palynological data. Using well-dated diagrams going back to the early Holocene, main regional vegetation phases were derived: the Betula–Pinus phase (ca. 11 600–10 200 cal yr BP), the Corylus phase (ca. 10 200–9000 cal yr BP), the Picea phase (ca. 9000–6000 cal yr BP), the Fagus–Picea phase (ca. 6000–4500 cal yr BP), the Abies–Fagus–Picea phase (ca. 4000–1000 cal yr BP), and the anthropogenic vegetation phase (ca. 1000–0 cal yr BP). Some diagrams show the presence or even continuous curves of potential pasture and meadow indicators from around 2000 cal BCE at the earliest. Even cereal pollen grains occur sporadically already before the High Medieval. These palynological indications of a local prehistoric human impact also in the higher altitudes find parallels in the (geo-)archaeologically proven Bronze Age tin placer mining and in the geochemically proven Iron Age metallurgy in the Erzgebirge. The pollen data show that immediately before the medieval clearing, i.e. beginning at the end of the 12th century CE, forests were mainly dominated by Fagus and Abies and complemented by Picea with increasing share towards the highest altitudes. According to historical data, the minimum of the regional forest cover was reached during the 17th–18th centuries CE. The dominance of Picea in modern pollen spectra is caused by anthropogenic afforestation in the form of monocultures since that time. Future palynological investigations, preferably within the framework of altitudinal transect studies, should aim for chronologically and taxonomically high-resolution and radiometrically well-dated pollen diagrams from the larger peatlands.

Simulating the Effects of Regional Forest Cover and Windthrow‐Induced Cover Changes on Mid‐Latitude Boundary‐Layer Clouds

AbstractEvidence has been provided that land‐cover changes such as deforestation can have an impact on cloudiness and precipitation. However, conflicting results have been obtained at different scales and places, highlighting our poor understanding of the physical processes involved. Here we focus on mesoscale summer cloudiness in a temperate region, as influenced by a large forest massif (the Landes forest in France). Our study is based on an up‐to‐date atmosphere‐surface mesoscale model (Meso‐NH coupled with SURFEX). Based on observational data, we first optimize the model configuration for our purpose, and show that with a 500 m horizontal resolution we can successfully simulate the higher summer cloud cover observed over the forest, compared to its surroundings. Second, we investigate the physical processes leading to cloud formation in a representative case study. Based on a comparative analysis of diagnostics and budgets over forest and non‐forest areas, we find that the larger sensible heat flux over the forest and its higher roughness are the main drivers of cloudiness, enhancing vertical velocity and boundary‐layer mixing. Third, we simulate the impact of the 2009 Klaus storm that led to the loss of about one third of the trees. Considering 15 representative convective summer days, we show that the model simulates well the resulting decrease in summer cloudiness that was reported in a previous study based on satellite observations. As a complementary tool, the mesoscale simulations allow to quantify the impacts of the Klaus storm windthrow on the diurnal cycle of the boundary layer.

Devolution of tenure rights in forestland in China: Impact on investment and forest growth

I investigate whether devolution of forestland tenure rights to households in China triggered forest investment and the impact on forest conditions. I use a panel dataset of a two-round survey of over 10,000 forestland plots held by 1500 households in eight provinces before and after the devolution. Using a quasi-experimental regression approach, I find that forestland devolved to households has higher per-area-unit, yearly labor input and capital investment. I also find larger forest cover in regions devolving more. The findings support that clearly-defined and well-protected household property rights offer an effective alternative to common-pool resources management in small-scale forestry.

Contribution of ‘human induced fires’ to forest and savanna land conversion dynamics in the Luki Biosphere Reserve landscape, western Democratic Republic of Congo

ABSTRACT Human-induced fire is one of the most important determinants of forest cover and change in tropical and subtropical regions of the world. Yet its impact on forest cover and forest cover change remains unclear, as fires in Africa generally do not spread over very large area. This is particularly the case in the Democratic Republic of Congo (DRC), a region of the world that is still poorly investigated. Here, we propose to study the effect of human-induced fire on land use and land cover change in a protected area of the DRC, i.e. the Luki Biosphere Reserve (LBR). We investigate tree cover changes in and around the reserve between 2002 and 2019 using Landsat 7 ETM+, Landsat 8 OLI/TIRS and MODIS MCD12Q1 images and quantify human induced fires using MODIS MCD64A1 images. The study combines land use and land cover (LULC) change detection analysis of four images, two acquired in 2002 and two acquired in 2019, with multi-temporal assessment of annual burnt area acquired between 2002 and 2019 from MODIS MCD64A1 to assess the role of fire in LULC changes and the sensitivity of different LULC types to fire. The results show a dynamic conversion of primary forest to secondary forest over about 16% of the area, the evolution of savanna to secondary forest over 9.6% (Landsat image) and the replacement of secondary forest by savanna over 8.1% (MODIS image) of the total area of Luki Reserve. Of the total area undergoing land use change, 34.1% (Landsat image) and 35.7% (MODIS image) were caused by fire, which however did not cause a significant LULC change. For the LULC types that experienced fire events, the least stable type was primary forest, which had the lowest stability rate (34.2% and 23% for Landsat and MODIS image analysis, respectively) compared to others. This result illustrates the importance of fire as a driver of primary forest loss and degradation in the region. Despite the high exposure of savannas to fire events, they were not significantly destabilized by fire (stability rates of 86.3 and 97% for Landsat and MODIS analysis, respectively). Future analyses should focus on discriminating between different fire types to better understand the complex relationship between fire and ecosystem conditions.

A regional view of the linkages between hydro‐climatic changes and deforestation in the Southern Amazon

AbstractIn the last four decades, the Southern Amazon (south of 8°S) has shown changes in the spatial and temporal patterns of its hydro‐climatic components, leading to drier conditions. Due to climate and land‐use changes, this region is considered as a zone under biophysical transition processes. Previous studies have documented a complex interaction between climate and deforestation either on a large‐scale or based on limited in situ data, typically covering the Brazilian Amazon. In this study, we analyse the relationships between hydro‐climate, the surface water‐energy partitioning and an index of regional forest cover change for the period 1981–2018. Additionally, we discretized three regions covering the Bolivian Amazon and the southern portions of the Peruvian and Brazilian Amazon due to their differences in the evolution of land use. In the Bolivian region, a high ratio of forest cover change, exceeding 40–50%, is related to a significant tendency to become water‐limited. This change is associated with decreased rainfall, increased potential evapotranspiration and decreased actual evapotranspiration. Regardless of the region analysed, those that are characterized by a high ratio of forest cover change (>40–50%) show growing imbalance between increasing potential and decreasing actual evapotranspiration. However, in the Peruvian and Brazilian regions, hydro‐climatic conditions remain energy‐limited due to minor rainfall changes. The observed differences in surface water‐energy partitioning behaviour evidence a complex dependence of both sub‐regional (i.e., land cover changes) and large‐scale (i.e., strengthening of the Walker and Hadley circulations) conditions. Our findings indicate a clear link between hydro‐climatic changes and deforestation, providing a new perspective on their spatial variability on a sub‐regional scale.

What determines the distribution of a threatened species, the brush‐tailed phascogale Phascogale tapoatafa (Marsupialia: Dasyuridae), in a highly modified region?

AbstractIdentifying factors that affect species’ distributions in highly modified landscapes, especially threatened species, is a key issue for conservation worldwide. Three types of factors commonly are considered important: the extent and pattern of suitable habitat at a landscape scale; the availability of key resources at a local scale; and interactions with other species. The brush‐tailed phascogale (Phascogale tapoatafa) has undergone range contractions and regional extinctions in Australia and falls within the critical weight range of mammal species with high risk of decline. Yet, in some regions, it persists despite marked habitat loss and disturbance. We investigated the distribution of the brush‐tailed phascogale in a highly modified region in central Victoria where it is a ‘flagship’ for community conservation. At 50 sites, stratified geographically and in relation to topography and surrounding forest cover, we carried out surveys using remotely sensed cameras (in parallel with nest box inspections). We used an occupancy modelling framework and information‐theoretic approach to analyse factors influencing detectability and occupancy. The brush‐tailed phascogale was widespread, recorded at 84% (42/50) of sites. The environmental space occupied by sites with camera records matched that of nest boxes containing established nests of this species. Detection probability was influenced by survey effort and site‐level measures of habitat quality (logs, litter, topographic position) likely reflecting population abundance. Dry forested slopes were favoured compared with gullies. The study area, with its dry forests of rough‐barked eucalypts, is a stronghold for this species. The broad distribution of the brush‐tailed phascogale in this highly modified region can be attributed to retention of ˜36% regional forest cover and a relatively high level of structural and functional connectivity. In such modified landscapes, complementary actions by land managers to sustain remaining large tracts of forest and also a mosaic of wooded vegetation across the rural landscape will help such species to persist.

АНАЛІЗ РЕСУРСНОГО ПОТЕНЦІАЛУ В КОНТЕКСТІ ФОРМУВАННЯ КОНКУРЕНТОСПРОМОЖНОСТІ ЛІСОГОСПОДАРСЬКОГО КОМПЛЕКСУ УКРАЇНИ

The article presents an analysis of the forest resource potential of Ukraine according to certain criteria in the dynamics. Positive trends of its growth in the context of formation of competitiveness of forestry complex are proved, in particular: increase of the area of lands of forestry purpose for 50 years by 21% and achievement of level of forest cover of the territory to 15,9% (optimum level – 20%); increase in the stock of stands per 1 ha in up to 240 m3 (7th place in Europe); exceeding the volume of forest reproduction area by 6% for the area of continuous fellings, which indicates the inexhaustible activity of the forest industry. Negative tendencies of deterioration of the forest resource potential of the country were determined, in particular: high share of medieval stands (47.5%) and low share of mature and overripe plantations (18.7%), high average age of stands (over 60 years); most of the forest plantations are created artificially, which causes their low immunity to forest pests and various diseases, on half of the lands covered with forest vegetation it is forbidden to carry out felling of the main use, which reduces the full use of resource potential of the industry; most forests are state-owned, 13% are permanently used by utilities, and the share of privately owned forests is less than 0.1%. More than 7% of forest plantations are classified as reserve lands, and another part is subordinated to dozens of central government agencies, which leads to their decline and inefficient use. Thus, as a result of the analysis, the necessary directions for improving the condition of certain components of the forest resource potential in the context of strengthening the competitiveness of the forestry complex are substantiated. It is proposed to review the existing distribution of forest lands by various permanent users and by different categories of protection, which leads mainly to the decline and inefficient use of forest stands in the country. Negative manifestations in the functioning of the forest sector are also the high average age of plantations, a significant proportion of artificial plantations and the insufficient level of forest cover in some administrative regions.

Assessing Drivers of Deforestation and Forest Degradation in PirPanjal Region of Kashmir Himalayas using Geospatial Approach

Global deforestation is a major contributor of CO 2 emission despite registering slowdown in the past decade. Regional forest cover change, a cause of climatic concern is attributed to increasing anthropogenic pressure on forests. Focus on drivers of forest cover change has become inevitable due to global emphasis on role of socio-economic framework in conserving forests. Keeping in view, the study was aimed to assess deforestation and forest degradation and identify drivers of change in PirPanjal region of Western Himalaya using Landsat Thematic Mapper (TM) data of 2003 and 2013. Satellite data was delineated into different categories of forest cover namely closed forest, open forest, forest scrub, grasslands and non-forest using on-screen visual interpretation. Mapping was supplemented with extensive field validation points for accuracy assessment. Forest cover change map and change matrix were generated to assess rates of deforestation. Drivers of change were assessed through a detailed semi-structured interview schedule. The results revealed a gross annual deforestation of -0.46% and a net annual deforestation of -0.45%. Illicit felling, poverty and lack of employment were identified to be the top drivers of deforestation and forest degradation while as plantation and afforestation reassured forest growth at some places. There is a need to prioritize actions for restoration and conservation of some areas based on identified drivers to reverse the process of deforestation and forest degradation. The locations indicating negative change can be strategized under REDD+ mechanism for reclamation of forests with integrated social benefits.

Reversals of Reforestation Across Latin America Limit Climate Mitigation Potential of Tropical Forests

Carbon sequestration through tropical reforestation and natural regeneration could make an important contribution to climate change mitigation, given that forest cover in many tropical regions increased during the early part of the 21st century. The size of this carbon sink will depend on the degree to which second-growth forests are permanent and protected from re-clearing. Yet few studies have assessed permanence of reforestation, especially not at a large spatial scale. Here, we analyzed a 14-year time series (2001-2014) of remotely sensed land-cover data, covering all tropical Latin America and the Caribbean, to quantify the extent of second-growth forest permanence. Our results show that in many cases, reforestation in Latin America and the Caribbean during the early 21st century reversed by 2014, limiting carbon sequestration. In fact, reversals of reforestation, in which some or all gains in forest cover in the early 2000s were subsequently lost, were ten times more common than sustained increases in forest cover. Had reversals of reforestation been avoided, forests could have sequestered 0.58 Pg C, over four times more carbon than we estimate was sequestered after accounting for impermanence (0.14 Pg), representing a loss of 75% of carbon sequestration potential. Differences in the prevalence of reforestation reversals across countries suggest an important role for socio-economic, political, and ecological context, with political transitions and instability increasing the likelihood of reversals. These findings suggest that national commitments to reforestation may fall short of their carbon sequestration goals without provisions to ensure long-term permanence of new forests.

Deconstructing Diets: The Role of Wealth, Farming System, and Landscape Context in Shaping Rural Diets in Ethiopia

Dietary diversification is central to improving dietary quality and nutrition for food security. Several factors have been linked to higher diversity diets, including household wealth, market access, on-farm crop diversity and regional forest cover. How these factors combine in landscapes to shape diets, however, is not well understood. We take the Ethiopian context as a case study of how wealth, farming system type, and landscape context interact to explain household dietary profiles. Using cluster analysis on nationally representative data on household food consumption, we identify three distinct dietary profiles across rural Ethiopia: 1) A low diversity diet, 2) A diverse diet particularly rich in fruit and vegetables, and 3) A diverse diet also rich in oils, fats and sugars. We found that the low diversity diet was strongly associated with households in the bottom and middle wealth classes that were mostly involved in cereal-based farming, although not exclusively. In contrast, the diverse diet high in fruit and vegetables was primarily composed of households with coffee-agroforestry farming systems, and did not appear to be limited to any particular wealth class, although it was positively associated with forest cover. Households with a diverse diet profile also rich in oils, fats and sugars were stratified across multiple different farming types, situated closer to roads, and primarily came from the middle and top wealth classes. Finally, while forest cover was strongly associated with a dietary profile rich in fruits and vegetable and the pursuit of coffee-agroforestry farming, the forest cover in cereal-based systems was still significantly positively associated with the consumption of dark green leafy vegetables and fruits. This suggests that even small amounts of forest cover can contribute to healthy diets. These results, which illuminate how wealth, farming system type, and landscape context shape dietary profiles, have important implications for the design of effective food security policies in Ethiopia.

Rainfall anomalies are a significant driver of cropland expansion

Rainfall anomalies have long occupied center stage in policy discussions, and understanding their impacts on agricultural production has become more important as climate change intensifies. However, the global scale of rainfall-induced productivity shocks on changes in cropland is yet to be quantified. Here we identify how rainfall anomalies impact observed patterns of cropped areas at a global scale by leveraging locally determined unexpected variations in rainfall. Employing disaggregated panel data at the grid level, we find that repeated dry anomalies lead to an increase in cropland expansion in developing countries. No discernible effects are detected from repeated wet events. That these effects are confined to developing countries, which are often dominated by small-holder farmers, implies that they may be in response to reduced yields. The estimates suggest that overall, in developing countries, dry anomalies account for ∼9% of the rate of cropland expansion over the past two decades. We perform several tests to check for consistency and robustness of this relationship. First, using forest cover as an alternative measure, we find comparable reductions in forest cover in the same regions where cropland expands due to repeated dry anomalies. Second, we test the relationship in regions where yields are buffered from rainfall anomalies by irrigation infrastructure and find that the impact on cropland expansion is mitigated, providing further support for our results. Since cropland expansion is a significant driver of deforestation, these results have important implications for forest loss and environmental services.

Human occupation, slash-burning and vegetation response from the final Pleistocene to the middle Holocene, Daling River basin, NE China

We present new radiocarbon dating, pollen and microcharcoal date from a section at a well-known early Neolithic site, Chahai, in Northeast China, to reconstruct vegetation and human occupation history and to evaluate human influence on the regional vegetation. The results suggested that the site was occupied in at least four main stages, 12,700–12,570, 10,200–9300, 7200–6300 and 2070–1920 cal yr BP, and that the periodic occupation and abandonment of the Chahai site was probably related to global millennial scale climate change. The regional vegetation change in Chahai region showed an increasing trend in humidity from the final Pleistocene to the middle Holocene; the vegetation was successively dominated by an arid steppe (12,700–12,570 cal yr BP) and moist meadow (10,200–9300 and 7200–6300 cal yr BP). Nevertheless, the reduction of the regional forest cover, indicated by a decrease in the proportion of tree pollen, was synchronous with population expansion locally around 7200–6300 cal yr BP. Our results demonstrate that the vegetation succession in the Chahai region was mainly controlled by climate change in the final Pleistocene and the early Holocene (12,700–12,570 and 10,200–9300 cal yr BP), while increased human activities and agricultural behavior played major roles in the degradation of the regional forest during the middle Holocene (7200–6300 cal yr BP).

Identifying Biases in Global Tree Cover Products: A Case Study in Costa Rica

Global tree cover products are widely used in analyses of deforestation, fragmentation, and connectivity, but are rarely critically assessed. Inaccuracies in these products could have consequences for future decision making, especially in data-poor regions like the tropics. In this study, potential biases in global and regional tree cover products were assessed across a diverse tropical country, Costa Rica. Two global tree cover products and one regional national forest cover map were evaluated along biophysical gradients in elevation, precipitation, and agricultural land cover. To quantify product accuracy and bias, freely available high-resolution imagery was used to validate tree and land cover across these gradients. Although the regional forest cover map was comparable in accuracy to a widely-used global forest map (the Global Forest Change of Hansen et al., also known as the GFC), another global forest map (derived from a cropland dataset) had the highest accuracy. Both global and regional forest cover products showed small to severe biases along biophysical gradients. Unlike the regional map, the global GFC map strongly underestimated tree cover (>10% difference) below 189 mm of precipitation and at elevations above 2000 m, with a larger bias for precipitation. All map products misclassified agricultural fields as forest, but the GFC product particularly misclassified row crops and perennial erect crops (banana, oil palm, and coffee), with maximum tree cover in agricultural fields of 89%–100% across all crops. Our analysis calls into further question the utility of the GFC product for global forest monitoring outside humid regions, indicating that, in tropical regions, the GFC product is most accurate in areas with high, aseasonal rainfall, low relief, and low cropland area. Given that forest product errors are spatially distributed along biophysical gradients, researchers should account for these spatial biases when attempting to analyze or generate forest map products.

The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions

Characterised by a maximum expansion of continental ice sheets in the Northern Hemisphere, Marine Isotope Stage (MIS) 12 (∼478–424 ka before present) was one of the strongest glacials of the Quaternary. Because the information currently available on MIS 12 is predominantly derived from marine records, the imprint of this extreme glaciation on the terrestrial realm – and notably on terrestrial ecosystems – has remained poorly constrained. Here we present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula, SE Europe) augmented by pollen-based quantitative temperature and precipitation estimates. Our dataset, which spans the period from 488 to 420 ka, shows that the forest cover around Lake Ohrid decreased substantially over the course of MIS 12; this decrease was associated with a gradual lowering of winter and mean annual temperatures (and to a lesser extent of summer temperatures) as well as mean annual precipitation. Superimposed on this long-term development, abrupt changes in regional forest cover indicate a pronounced millennial-scale climate variability that bears strong resemblance to the interstadial and stadial events of the Last Glacial. This variability is expressed by repeated high-amplitude forest expansions and contractions around Lake Ohrid during MIS 12c and the oldest part of 12b substage (i.e., from ∼477 to 448 ka). The forest oscillations can be correlated to previously documented episodes of surface-water variability and ice-rafted debris deposition in the North Atlantic. This pattern suggests a coupling between the climatically forced tree-population changes in SE Europe and the variability of the Atlantic Meridional Ocean Circulation during MIS 12c and partially 12b on millennial timescales. In contrast, the youngest part of MIS 12b and MIS 12a (i.e., from ∼448 to 424 ka) lack high-amplitude forest expansions and contractions around Lake Ohrid. Comparison with sea-level reconstructions for MIS 12 suggests that millennial-scale vegetation variability in Lake Ohrid was strongest when sea level was between 30 and 100 m lower than today, whereas it was absent when sea level was lower than 100 m relative to the present.