Surface Water Changes Research Articles

Surface water, vegetation, and fire as drivers of the terrestrial Arctic-boreal albedo feedback

The Arctic is warming twice as fast as the global average, due in part to the albedo feedbacks of a diminishing cryosphere. As snow cover extent decreases, the underlying land is exposed, which has lower albedo and therefore absorbs more radiation, warming the surface and causing a positive feedback to climate change. Changes in terrestrial snow-free albedo (e.g. changes in vegetation or surface water) could also affect Earth’s energy balance, but their importance for contemporary climate change is relatively unknown. Here we show that changes in surface water are significantly altering Artic-boreal albedo, and explain up to 27% of the spatial variation in monthly albedo change from 2000 to 2019. The increase in radiative forcing due to changes in surface water extent is most pronounced in the continuous permafrost zone, contributing to a positive feedback between permafrost thaw and climate change. Additionally, we show that fire history and changes in tree cover and surface water extent together account for at least 15% of albedo-induced radiative forcing over the study period, indicating that these processes are a regionally important aspect of the climate-albedo feedback.

Surface water–groundwater interactions of Xiluodu Reservoir based on the dynamic evolution of seepage, temperature, and hydrochemistry due to impoundment

AbstractReservoir construction greatly affects the regional ecological environment, particularly surface water–groundwater interactions around the reservoir. Xiluodu Reservoir, a representative large‐scale reservoir in China, has had substantial impacts on surface water–groundwater interactions at the dam site since impoundment. This study analysed the dynamic characteristics of surface water–groundwater level, temperature, and hydrochemistry to determine the evolution of surface water–groundwater interaction before and after the impoundment. The levels of groundwater and some surface water rose by more than 100 m after impoundment and the water level of saturated limestone gradually stabilized, whereas basalt saturation in the affected area continued to expand. The groundwater temperature did not decrease significantly, whereas the hydrochemical types and ion contents of both surface water and groundwater experienced significant changes. Calculation of the saturation index indicated spatiotemporal changes in the saturation state of minerals. The replenishment source of each type of water and their mutual relationships were determined using cluster analysis and isotope characteristics. The results confirmed continuous, significant, and variable surface water–groundwater interactions at the dam site, which were partially reversed after impoundment. Changes in surface water–groundwater interactions were due to impoundment, the impact of which decreases with distance from the dam, as well as the unique geological conditions and artificial construction.

Assessing Climate Change Trends and Their Relationships with Alpine Vegetation and Surface Water Dynamics in the Everest Region, Nepal

The Himalayas, especially the Everest region, are highly sensitive to climate change. Although there are research works on this region related to cryospheric work, the ecological understandings of the alpine zone and climate impacts are limited. This study aimed to assess the changes in surface water including glacier lake and streamflow and the spatial and temporal changes in alpine vegetation and examine their relationships with climatic factors (temperature and precipitation) during 1995–2019 in the Everest region and the Dudh Koshi river basin. In this study, Landsat time-series data, European Commission’s Joint Research Center (JRC) surface water data, ECMWF Reanalysis 5th Generation (ERA5) reanalysis temperature data, and meteorological station data were used. It was found that the glacial lake area and volume are expanding at the rates of 0.0676 and 0.0198 km3/year, respectively; the average annual streamflow is decreasing at the rate of 2.73 m3/s/year. Similarly, the alpine vegetation greening as indicated by normalized difference vegetation index (NDVI) is increasing at the rate of 0.00352 units/year. On the other hand, the annual mean temperature shows an increasing trend of 0.0329 °C/year, and the annual precipitation also shows a significant negative monotonic trend. It was also found that annual NDVI is significantly correlated with annual temperature. Likewise, the glacial lake area expansion is strongly correlated with annual minimum temperature and annual precipitation. Overall, we found a significant alteration in the alpine ecosystem of the Everest region that could impact on the water–energy–food nexus of the Dudh Koshi river basin.

High-accuracy continuous mapping of surface water dynamics using automatic update of training samples and temporal consistency modification based on Google Earth Engine: A case study from Huizhou, China

Surface water is experiencing significant changes due to anthropogenic activities and climate change. Recent studies have explored long-term surface water dynamics with the development of multi-source remote sensing data and mapping technology. However, cost-effective and time-saving reliable references for mapping surface water from remote sensing images at multiple times are still lacking. Further, negligence of abnormal changes in time-series surface water maps seriously affects surface water mapping accuracy. In this study, we propose a high-accuracy method for long-term mapping of surface water by automatic update of training samples and temporal consistency modification in surface water sequences. Taking the surface water in Huizhou from 1986 to 2020 as a case study, the method is applied and tested. Temporal training samples were updated through Robust Mahalanobis distances and statistical filtering. Combined with the random forest algorithm and the Google Earth Engine platform, annual surface water maps were generated. A method for temporal consistency detection in moving window and abnormal changes modification rule with intra-annual information are proposed to improve annual surface water mapping accuracy. The accuracy of surface water dynamics and abnormal water modifications were quantified as 89.8% and 95.7%, respectively. With our proposed method, the resultant maximum annual water areas of Huizhou were detected, with a statistically significant upward trend and net increase of 103.1 km2 over 35 years. Reservoir construction and aquaculture expansion constitute the main sources of increased waters in this case study. It is demonstrated that our proposed method offers important advantages in terms of the accuracy of annual surface water maps and especially change monitoring.

Modelling lake water's surface changes using environmental and remote sensing data: A case study of lake urmia

A synthesis approach known as modeling lake water changes model (LWC-model) was proposed in this research for assessing, conserving, and managing the water stability of lakes. The proposed LWC model was divided into two parts: assessment of satellite-derived water feature and spatiotemporal modelling. The LWC model was empirically evaluated using multi-temporal Landsat data, environmental criteria, and Urmia lake restoration programs (ULRP) criteria, and the results were compared to its stable situation (i.e., 2002). Initially, several water indices were studied for extracting surface water. Following that, one of these indices that outperformed the others when compared to the reference map was employed in the suggested method. Second, three economic strategies were used to examine the environmental and government ULRP requirements. The first part's findings revealed a significant reduction in lake water surface of about 58.22% between 2002 and 2014, followed by a 37% rise between 2014 and 2018. These gradual variations in water level may be ascribed to two primary criteria: the ULRP requirements for Lake Urmia resurrection and environmental variables. This stability would be somewhat fragile if ULRP recovery operations on the lake were not undertaken due to the generally steady climatic conditions. Furthermore, the findings of the three strategies revealed that the lowest, average, and maximum time necessary for Lake Urmia to return to a stable state, were 10, 20, and 39 years, respectively. The LWC model used a versatile method that could be applied to any body of water given the new criteria and parameters. To summarize, the approach we presented can be suggested for modeling and mapping inland water, specifically lake water fluctuations in other favorable areas with comparable meteorological and environmental circumstances.

Remote sensing monitoring of monthly surface water changes in Bosten Lake (1990-2020)

Climate change and human activities have led to changes in the lake surface water, monitoring the long-term monthly changes of the lake surface water is of great significance to maintain the ecological balance of lakes. Based on the Landsat images and Google Earth Engine (GEE), we monitored the bi-monthly dynamics of the surface water of Bosten Lake in the past 30 years. The results show that: in the past 30 years, the maximum surface water of the lake is 1167.18 km2; the inter-annual dynamics of Bosten Lake surface water were divided into four stages: sharp decrease during 1990-1991, increase during 1992-2002, decrease again during 2003-2012, and finally recovery from 2013 to 2020; the annual changes of lake surface water have a certain pattern, decreasing from March to July, increasing from July to September, and then starting to decrease again. The inter-annual variability of the surface water of Bosten Lake was mainly affected by human activities and climate factors.

Assessment of the state of the Protoka river water system by toxicological and bioindicative indicators

Water resources are one of the most important, but at the same time the most impressible components of the environment. This component is able to change very quickly under the influence of economic and human activities. The constant growth of anthropogenic pressure on the hydrosphere, changes in water regime and surface water reserves cause to impairment of quantitative and qualitative indicators of surface water. Biological tests play a special role in assessing the environment state. The results of chemical analysis performed with the help of complex equipment, in many cases do not allow assessing the true danger of pollutants on the environment, to predict the effects of their impact on living organisms. Various pollutants, getting into the environment, can undergo transformations, while increasing their toxic effects. For this reason, methods of integrated assessment of the quality of the aquatic environment are necessary. Biotesting methods play a huge role in this. Biotestingis used for express control over industrial waste, control of technological processes in real time; to determine the level of toxicity of new products, to control the toxic effects of materials, drugs, food, to determine the quality of drinking water, etc. The methodological possibilities of studying the toxicity of various substances on test organisms have significantly expanded over the last twenty years. We are intensively searching for the most sensitive test objects and indicators. Instrumental methods of analysis are being worked out. Various methods are used to assess the quality of the aquatic environment, changes in the parameters of physiological systems and the biochemical status of test organisms, test organs.The Protoka River ecological condition in Bila Tserkva district of Kyiv region was studied by bioindication methods (study of fluctuating asymmetry of aquatic organisms’ development, growth test to establish phytotoxicity of water and coastal soil). Toxicological investigation (pH determination, TDS, content of heavy metals in the coastal soil) were set. Histological parameters of silver carp parenchymal organs were conducted. Changes in the histostructure of the liver and kidneys of silver carp were detected. They indicate unfavorable conditions for fish. The obtained results can be used for ecological monitoring of the aquatic environment.

The Cold Region Critical Zone in Transition: Responses to Climate Warming and Land Use Change

Global climate warming disproportionately affects high-latitude and mountainous terrestrial ecosystems. Warming is accompanied by permafrost thaw, shorter winters, earlier snowmelt, more intense soil freeze-thaw cycles, drier summers, and longer fire seasons. These environmental changes in turn impact surface water and groundwater flow regimes, water quality, greenhouse gas emissions, soil stability, vegetation cover, and soil (micro)biological communities. Warming also facilitates agricultural expansion, urban growth, and natural resource development, adding growing anthropogenic pressures to cold regions’ landscapes, soil health, and biodiversity. Further advances in the predictive understanding of how cold regions’ critical zone processes, functions, and ecosystem services will continue to respond to climate warming and land use changes require multiscale monitoring technologies coupled with integrated observational and modeling tools. We highlight some of the major challenges, knowledge gaps, and opportunities in cold region critical zone research, with an emphasis on subsurface processes and responses in both natural and agricultural ecosystems.

Effects of Extreme Climate Change in 2016 and Its Correlation with EWH Variability in Indonesia

Gravity Recovery and Climate Experiment (GRACE) satellite mission, which is dedicated specifically to the Earth’s gravity change monitoring, also can be used to observe water mass variations. GRACE data is provided through temporal mass variations, primarily water volume variations such as surface water and groundwater changes. GRACE satellite data can be obtained in monthly spherical harmonics coefficients depicting the change of surface mass density. This study investigates the effects of extreme climate change during 2016 in Indonesia by utilizing the GRACE data. Here, the surface mass density change is converted into equivalent water height (EWH). Since the amount of rainfall in Indonesia indirectly dominates the water mass variability, the EWH is then compared with the precipitation over the same period of this study. The result showed that during 2016, the highest and lowest EWH was presented in August with the highest value of 23.527 cm over the Aceh region and the lowest EWH of 0.665 cm over the Nusa Tenggara region. The most increased precipitation during 2016 is in the Kalimantan region, with a value of 0.610 mm/hr in February. The lowest one is in the Nusa Tenggara region, with a value of 0.009 mm/hr in August. For comparison with the EWH, the precipitation rates were converted into monthly precipitation in cm. The correlations between EWH and precipitations variabilities showed different results in different study zones, with the highest correlation in zone 6, which covers North Kalimantan. In comparison, the lowest correlation occurred in zone 25, which covers Yamdena and Tragan islands_ area in the Moluccas

Surface Water Changes in Dongting Lake from 1975 to 2019 Based on Multisource Remote-Sensing Images

Dongting Lake plays an important role in water regulation and biodiversity protection, but it is vulnerable to climate change and human activities. To quantify surface water changes and factors driving them, long-term surface water variation in Dongting Lake was investigated using the multiple spectral indices method based on a decision tree classification for full time-series Landsat and MODIS datasets. Factors influencing surface water changes were explored by combining the annual maximum surface water and annual permanent occurrent water with meteorological and hydrological data. The results showed that both annual maximum surface water and annual permanent water decreased from 1975 to 2019 and the trends of rainfall and runoff at three outlets also changed. The annual maximum surface water surface of Dongting Lake increased during the 1990s due to high rainfall but decreased again after 2000. A significant change in both the hydrological stage and surface water sequence from 1986 to 2019 occurred in 2003, which coincided with the beginning of work to construct the Three Gorges Dam (TGD). The surface water decreased by about 360 km2 and runoff at the three outlets decreased by about 150 × 108 m3 after the impoundment of the TGD, which was likely the main cause of surface water changes after 2003. The area of surface water that changed from permanent water in the pre-TGD period into seasonally occurring water in the post-TGD periods is 209 km2, while the area of surface water that changed from seasonally occurring water in the pre-TGD period into permanent occurrent water in the post-TGD period is 31 km2. Meteorological elements and human activities have had a comprehensive impact on surface water changes in Dongting Lake. Rainfall and temperature account for about one-third of the influence on long-term changes of surface water, and rainfall is the main meteorological driving factor of surface water in the wet season, while temperature is the main factor in the dry season. Runoff at three outlets, four rivers and the Chenglingji explain about half of the change in surface water; the three outlets runoff is mainly affected by human activities and is the main hydrological driving factor of surface water. The monthly maximum surface water fluctuates regularly and Dongting Lake has a strong seasonal characteristic. Indeed, the seasonal changes are significantly altered when drought or flooding occurs, the causes of which are diverse and complex.

Improved Hydrological Loading Models in South America: Analysis of GPS Displacements Using M-SSA

Environmental loading, in particular from continental water storage changes, induces geodetic station displacements up to several centimeters for the vertical components. We investigate surface deformation due to loading processes in South America using a set of 247 permanent GPS (Global Positioning System) stations for the 2003–2016 period and compare them to loading estimates from global circulation models. Unfortunately, some of the hydrological components, and in particular surface waters, may be missing in hydrological models. This is especially an issue in South America where almost half of the seasonal water storage variations are due to surface water changes, e.g., rivers and floodplains. We derive river storage variations by rerouting runoffs of global hydrology models, allowing a better agreement with the mass variations observed from GRACE (Gravity Recovery and Climate Experiment) mission. We extract coherent seasonal GPS displacements using Multichannel Singular Spectrum Analysis (M-SSA) and show that modeling the river storage induced loading effects significantly improve the agreement between observed vertical and horizontal displacements and loading models. Such an agreement has been markedly achieved in the Amazon basin. Whilst the initial models only explained half of the amplitude of GPS, the new ones compensate for these gaps and remain consistent with GRACE.

Temporal Patterns of Quality Surface Water Changes

Temporal Patterns of Quality Surface Water Changes

Simultaneous attenuation of trace organics and change in organic matter composition in the hyporheic zone of urban streams

Trace organic compounds (TrOCs) enter rivers with discharge of treated wastewater. These effluents can contain high loads of dissolved organic matter (DOM). In a 48 h field study, we investigated changes in molecular composition of seven DOM compound classes (FTICR-MS) and attenuation of 17 polar TrOCs in a small urban stream receiving treated wastewater. Correlations between TrOCs and DOM were used to identify simultaneous changes in surface water and the hyporheic zone. Changes in TrOC concentrations in surface water ranged between a decrease of 29.2% for methylbenzotriazole and an increase of 152.2% for the transformation product gabapentin-lactam. In the hyporheic zone, only decreasing TrOC concentrations were observed, ranging from 4.9% for primidone to 93.8% for venlafaxine . TrOC attenuation coincided with a decline of molecular diversity of easily biodegradable DOM compound classes while molecular diversity of poorly biodegradable DOM compound classes increased. This concurrence indicates similar or linked attenuation pathways for biodegradable DOM and TrOCs. Strong correlations between TrOCs and DOM compound classes as well as high attenuation of TrOCs primarily occurred in the hyporheic zone. This suggests high potential for DOM turnover and TrOC mitigation in rivers if hyporheic exchange is sufficient.

GRACE products and land surface models for estimating the changes in key water storage components in the Nile River Basin

The Nile River Basin (NRB) is facing extreme demand for its water resources due to an alarming increase in population and the changing climate. The NRB is not compatible with ground-based in-situ observations owing to its large basin area size and limited hydrological data access from basin countries. Thus, it lends itself to remotely sensed approaches with high spatial resolution and extended temporal coverage. The Gravity Recovery and Climate Experiment (GRACE) avails a unique opportunity to investigate the changes in key components of terrestrial water storage (TWS). GRACE TWS solutions have specific tuning parameters and processing strategies that result in regionally specific variations and error patterns. We explored the TWS time series spatiotemporal changes, trends, uncertainties, and signal-to-noise ratio among different GRACE TWS data. We had also investigated the key terrestrial water storage components such as surface water, soil moisture, and groundwater storage changes. The results show that GRACE spherical harmonic solutions' uncertainty is higher than the mass concentration (mascon) over the NRB, and the Center for Space Research-mascons had the best performance. The evapotranspiration correlation (R2 = 0.85) has the highest correlation with GRACE’s TWS, whereas the normalized difference vegetation index (R2 = 0.82) has the second highest correlation. Notably, significant long-term (2003–2017) negative groundwater and soil moisture trends demonstrate a potential depletion of the NRB. Despite an increase in precipitation and the TWS time series, the rate of decline increased rapidly after 2008, thereby indicating the possibility of human-induced change (e.g. for irrigation purposes). Therefore, the results of this study provide a guide for future studies related to hydro-climatic change over the NRB and similar basins.

Surface Water Extraction and Dynamic Analysis of Baiyangdian Lake Based on the Google Earth Engine Platform Using Sentinel-1 for Reporting SDG 6.6.1 Indicators

Surface water is an essential element that supports natural ecosystem health and human life, and its losses or gains are closely related to national or local sustainable development. Monitoring the spatial-temporal changes in surface water can directly support the reporting of progress towards the sustainable development goals (SDGs) outlined by the government, especially for measuring SDG 6.6.1 indicators. In our study, we focused on Baiyangdian Lake, an important lake in North China, and explored its spatiotemporal extent changes from 2014 to 2020. Using long-term Sentinel-1 SAR images and the OTSU algorithm, our study developed an automatic water extraction framework to monitor surface water changes in Baiyangdian Lake at a 10 m resolution from 2014 to 2020 on the Google Earth Engine cloud platform. The results showed that (1) the water extraction accuracy in our study was considered good, showing high consistency with the existing dataset. In addition, it was found that the classification accuracy in spring, summer, and fall was better than that in winter. (2) From 2014 to 2020, the surface water area of Baiyangdian Lake exhibited a slowly rising trend, with an average water area of 97.03 km2. In terms of seasonal variation, the seasonal water area changed significantly. The water areas in spring and winter were larger than those in summer and fall. (3) Spatially, most of the water was distributed in the eastern part of Baiyangdian Lake, which accounted for roughly 57% of the total water area. The permanent water area, temporary water area, and non-water area covered 49.69 km2, 97.77 km2, and 171.55 km2, respectively. Our study monitored changes in the spatial extent of the surface water of Baiyangdian Lake, provides useful information for the sustainable development of the Xiong’an New Area and directly reports the status of SDG 6.6.1 indicators over time.

Assessing the decoupling of economic growth from environmental impacts in industrial regions of the Russian Federation: an impact decoupling approach

The article analyzes the dynamics of the economic activity level in Russian industrial regions and its impact on the main environmental elements (water, air and soil) by calculating the decoupling coefficient. In the study a hierarchical cluster analysis was carried out, resulted in the formation of seven regional clusters, five of which had a significant share of the industrial sector in the gross value-added structure. Decoupling coefficients were calculated for 64 constituent entities of the Russian Federation belonging to different types of industrial clusters. The ecological and economic balance assessment of industrial regions growth showed the decoupling effect presence for most of them. The movement towards environmentally sustainable growth is more evident in the regions of the industrially diversified cluster. The analysis of three decoupling coefficients showed that in the vast majority of industrial regions the growth rates of pollutant emissions into the atmosphere and the growth rates of polluted wastewater discharges into surface water change at a lower rate than per capita GRP, which indicates a “green trend” in the region’s economic activity. However, the decoupling coefficient, showing the dynamics ratio of production and consumption waste and GRP per capita, has negative value in 37.5% of regions. The most problematic one in terms of this indicator was the Trade and manufacturing cluster, including 21 constituent entities of the Russian Federation. According to the authors, it may be related to the trade sector of these regions.

The Application of CYGNSS Data for Soil Moisture and Inundation Mapping in Australia

Cyclone global navigation satellite system (CYGNSS) has provided a valuable opportunity for high spatiotemporal monitoring of land surface reflectivity over the past few years. CYGNSS with a constellation of eight microsatellites is able to constantly observe the “scattered” global positioning system signals from the land. In this study, we validate the CYGNSS land reflectivity data in Australia for mapping the spatial extent of the inundated area and for determining temporal changes in surface soil moisture. CYGNSS level 1 data acquired for the period of 2017–2020 is assessed against various measurements, including satellite and ground-based measurements. Empirical mode decomposition is used to better analyze the CYGNSS time series and their relationship with the independent measurements. Furthermore, the mission's ability to capture surface reflectivity changes in response to extreme climatic events is analyzed. The results show that high spatial and temporal resolution CYGNSS data can largely represent the top layer ( $\sim$ 5 cm) soil moisture spatial and temporal variations close to soil moisture active passive. CYGNSS surface reflectivity results are also found to be sensitive to surface water changes and able to depict inundated land surface.

Discussion of different Remote sensing satellite possibilities for scientifical Earth observations

More than 1,000 satellites are launched into space, and they differ in their functions, rotation orbits, resolution, and other properties. Scientists divide the satellites into low-resolution, medium-resolution, high-resolution, and very high-resolution satellites by their properties. Now, the biggest challenge facing scientists is to use some of these different resolution images in their field. To get the expected result, it is very important to analyze the image that needs an which gives more accurate results. Therefore, the main attention of this article is aimed to find the answer to these problems. In this article 3 satellite images which have different resolution are analyzed. The possibility of middle-resolution images of MODIS, high-resolution images of Landsat, and very high-resolution images of WorldView-2 (WV-2) satellites using GIS are analyzed. A research area was the Syrdarya region, and downloaded different images of satellites of this area and compared with using e Cognition. According to the results, a more accurate satellite image for irrigation sets information is WorldView-2 images. In comparison analysis, it shows more accurate properties than other satellite images. As irrigation sets are small objects for the analysis, very high spatial resolution satellite images are important. Water discharge and surface change happen very fast; thus, it requires daily monitoring of the condition. And in this case, the temporal resolution of the MODIS and Landsat is 16 day, and it is a too long period.

Analysis of Surface Water Extraction and Change Detection Over Barur Lake, India

Water is one of the most essential and devastating element in the world. The lack of access to water and its abundance can be a serious threat to human life. These two circumstances may create a difficult situation against the sustainability of human life. Inadequate access to water causes drought, affects agriculture and on other side high level water availability in urban areas affects daily life. Hence, mapping and analysing of the surface water of the earth benefits from such impacts. Therefore, this study analysis evaluates the performance of available Landsat-8 OLI images for mapping water bodies and to obtaining precise Normalized Differential Water Index (NDWI) extraction. Change detection analysis of the obtained data shows that the area of the surface water body keeps on changing every year. The surface area of the lake has undergone a drastic change in the year 2019.

Complex causes and consequences of rangeland greening in South America – multiple interacting natural and anthropogenic drivers and simultaneous ecosystem degradation and recovery trends

Land-surface greening has been reported globally over the past decades. While often seen to represent ecosystem recovery, the impacts on biodiversity and society can also be negative. Greening has been widely reported from rangelands, where drivers and processes are complex due to its high environmental heterogeneity and societal dynamics. Here, we assess the complexity behind greening and assess its links to various drivers in an iconic, heterogeneous rangeland area, the Iberá Wetlands and surroundings, in Argentina. Time-series satellite imagery over the past 19 years showed overall net greening, but also substantial local browning both in protected and unprotected areas, linking to land use, temporal changes in surface water, fire, and weather. We found substantial woody expansion mainly in the unprotected land, with 37% contributed by tree plantations and the remaining 63% by spontaneous woody expansion, along with widespread transitions from terrestrial land to seasonal surface water. Fire occurrences tended to reduce greening with unprotected areas experiencing widespread and frequent fire. However, protected areas had more browning in unburnt areas than burned areas. Temporal variation in annual precipitation and temperature tended to nonlinearly influence fire occurrences with an interplay of human fire management, further shaping the vegetation greening, pointing to high complexity behind the observed rangeland greening involving interactions among local drivers. Our findings highlight that the observed overall greening is an outcome of multiple trends with clear negative impacts on biodiversity and the local livestock-oriented culture (notably expanding tree plantations) and spontaneous vegetation dynamics, partly involving spontaneous woody expansion. The latter has positive potential for biodiversity and ecosystem services in terms of woodland recovery, but can become negative in such a natural savanna region if expansions develop on a too broad scale, highlighting the importance of ensuring recovery of natural fire and herbivory regimes in protected areas along with sustainable rangeland management elsewhere.