Effects of ecological restoration projects on changes in land cover: A case study on the Loess Plateau in China

Quantifying spatiotemporal dynamics in the Kolonnawa marsh of Colombo, Sri Lanka

Kolonnawa marsh (KM) is an important wetland ecosystem in Colombo district, Sri Lanka that provides essential ecosystem services, and has undergone significant changes over recent decades due to continuous exploitation and reclamation. The values of wetlands are disregarded by decision-makers, despite the fact that they are crucial for improving the quality of water and offer chances for relaxation and amusement in metropolitan areas. Underestimation of the value of wetlands contributes to their continuing deterioration and inevitable loss. Investigating the changes in wetlands can provide crucial information for decision-making. This study aimed to monitor the spatiotemporal land-cover dynamics of KM with the prospect prediction as reduced total extent of KM gradually with time and marsh area being transformed into terrestrial vegetation with time. The collective images from Google Earth (2000 to 2021) and drone data (2022) were analyzed with the GIS application. Subsequently, 50-m2 grid squares with unique cell IDs are designed to link among land cover maps for spatiotemporal land-cover change analysis. Then, we calculate land cover category: surface water, marsh, and terrestrial vegetation proportions for each map in 50-m2 grid cells. Statistical comparison of the land cover changes in grid square cells shows that each land cover category has significant change with the time. The results showed that the reduction of KM marsh resulting in land cover changes has a positive implication on wetland degradation. Thus, interventions should be made for the restoration and sustainable management of KM.

Impact of land use/cover change and slope gradient on soil organic carbon stock in Anjeni watershed, Northwest Ethiopia

Today's agri-food systems face the triple challenge of addressing food security, adapting to climate change, and reducing the climate footprint by reducing the emission of greenhouse gases (GHG). In agri-food systems, changes in land use and land cover (LULC) could affect soil physicochemical properties, particularly soil organic carbon (SOC) stock. However, the impact varies depending on the physical, social, and economic conditions of a given region or watershed. Given this, a study was conducted to quantify the impact of LULC and slope gradient on SOC stock and C sequestration rate in the Anjeni watershed, which is a highly populated and intensively cultivated area in Northwest Ethiopia. Seventy-two soil samples were collected from 0-15 and 15-30 cm soil depths representing four land use types and three slope gradients. Soil samples were selected systematically to match the historical records (30 years) for SOC stock comparison. Four land use types were quantified using Landsat imagery analysis. As expected, plantation forest had a significantly (p < 0.05) higher SOC (1.94 Mg ha-1) than cultivated land (1.38 Mg ha-1), and gentle slopes (1-15%) had the highest SOC (1.77 Mg ha-1) than steeper slopes (> 30%). However, higher SOC stock (72.03 Mg ha-1) and SOC sequestration rate (3.00 Mg ha-1 year-1) were recorded when cultivated land was converted to grassland, while lower SOC stock (8.87 Mg ha-1) and sequestration rate (0.77 Mg ha-1 year-1) were recorded when land use changed from cultivation to a plantation forest. The results indicated that LULC changes and slope gradient had a major impact on SOC stock and C sequestration rate over 30 years in a highly populated watershed. It is concluded that in intensively used watersheds, a carefully planned land use that involves the conversion of cultivated land to grassland could lead to an increase in soil C sequestration and contributes to reducing the carbon footprint of agri-food systems.

From collapse to the health of the aquatic ecosystem in Dasha River (2006-2021): a case study of Shenzhen city in the Guangdong-Hong Kong-Macao Greater Bay Area, China

Compared with the aquatic ecosystem destruction caused by rapid urban development, substantial ecological restoration usually requires long periods and is a challenging process. Although river ecological restoration has been successful in different regions, the relationship between biodiversity, water quality, and effective measures applicable to developing countries remains poorly understood. This study was conducted in the Dasha River in Shenzhen city, one of the fastest-growing cities in China. The rehabilitation measures were sorted out in four phases to study the impact on water quality and biodiversity. In response, three campaigns were carried out to take phytoplankton, zooplankton, and benthos samples within the last three engineering stages, in 2007, 2012, and 2021. Synchronized investigations of water quality were conducted monthly from 2006 to 2021. Our analysis showed that the biodiversity of benthos has improved in recent years, which marks a turnaround for the aquatic ecological environment. According to the Hilsenhoff family biotic index (FBI), the water quality level in the 2021 campaign was promoted to "Good" in the downstream and "Fair" in the upper and middle streams. By analyzing Pearson's correlations between response ratios of water quality parameters and the Shannon-Wiener index of phytoplankton, zooplankton, and benthos, we concluded that biodiversity is significantly related to water quality. Specifically, the biodiversity of zooplankton is associated with ammonia nitrogen (NH₃-N) (R² =  - 0.77, P < 0.05), and benthos diversity is strongly negatively correlated with NH₃-N, total nitrogen, chemical oxygen demand, and biochemical oxygen demand (R² ≥ -0.82, P < 0.01). Despite the temporary negative impact of along-river interception on aquatic organisms in the campaign of 2012, the measures quickly and effectively improved water quality, which is the foundation for biodiversity improvement in 2021. This study provides insights into relationships among biodiversity, water quality, and regulation projects and can offer a reference for selecting aquatic ecosystem restoration measures in developing areas.

Land use and land cover dynamics and ecosystem services values in Kewet district in the central dry lowlands of Ethiopia

A better comprehensive and quantitative analysis of the tempo-spatial dynamics of land use and cover (LULC) in the dry lowlands areas of Ethiopia is crucial for restoring degraded landscapes. This study aimed at analyzing the trends of LULC changes and determine their ecosystem service values in Kewet district central dry lowlands of Ethiopia using multi-temporal satellite imagery for three periods: 1995, 2008, and 2017. Supervised classification, using the maximum likelihood classifier, was applied to quantify LULC changes. Ecosystem Service values were estimated using the modified ecosystem service value coefficients. LULC analysis showed that cultivated land was the most predominant which covered over 41% of the study area in all three periods. Forests showed a net increase of 18.2%. Shrubland occupied the second largest portion in all LULC analysis next to cultivated land, and it showed a net decrease of 29.2%. Open grassland showed a periodic increase. Over the past 20 years, built-up area and bared land grew continuously by 1.80 and 1.01 km² yr^-1, respectively. However, some degraded land was converted into woody vegetation land through area exclosure, which improved the vegetation coverage of the study area. Ecosystem Service values ranged from US$ 2.37 million for shrubland in 1995 to US$ 22.49 million for forest land in 2008. The total ESVs of the district also continuously decreased over the past two decades. Generally, the LULC in the Kewet district has been dynamic in that some of the LULC classes were expanding, while the others were shrinking through time.

Impacts of ecological restoration on public perceptions of cultural ecosystem services

Although ecological restoration has increased the stability and diversity of regional ecosystem services, its effects on public perceptions of cultural ecosystem services (CESs) remain unclear. Therefore, this study conducted a questionnaire survey of 455 interviewees in Ansai County on the Loess Plateau and combined the structural equation model (SEM) to explore the characteristics and influencing factors of public perceptions of CESs. Moreover, we also calculated landscape importance to quantify the impact of landscape features on CESs. The results showed that ecological restoration increased the overall public perceptions of CESs. Regarding the different types of CESs, the public most strongly perceived esthetic services but had the lowest perception of cultural heritage after ecological restoration. Regarding demographic characteristics, gender and age were the most important factors affecting public perceptions. Men were more likely to perceive CESs than women, while older interviewees had higher perceptions of the value of physical and mental health services, education and science than young interviewees. In addition, forestlands were perceived as playing more important roles than other landscape types in providing CESs. This study demonstrates that ecological restoration will improve public perceptions of CESs. Managers should incorporate public perceptions of CESs into the formulation of ecological management policies.

The changing face of floodplains in the Mississippi River Basin detected by a 60-year land use change dataset

Floodplains provide essential ecosystem functions, yet >80% of European and North American floodplains are substantially modified. Despite floodplain changes over the past century, comprehensive, long-term land use change data within large river basin floodplains are limited. Long-term land use data can be used to quantify floodplain functions and provide spatially explicit information for management, restoration, and flood-risk mitigation. We present a comprehensive dataset quantifying floodplain land use change along the 3.3 million km2 Mississippi River Basin (MRB) covering 60 years (1941-2000) at 250-m resolution. We developed four unique products as part of this work, a(n): (i) Google Earth Engine interactive map visualization interface, (ii) Python code that runs in any internet browser, (iii) online tutorial with visualizations facilitating classroom code application, and (iv) instructional video demonstrating code application and database reproduction. Our data show that MRB's natural floodplain ecosystems have been substantially altered to agricultural and developed land uses. These products will support MRB resilience and sustainability goals by advancing data-driven decision making on floodplain restoration, buyout, and conservation scenarios.

Mitigation of urbanization effects on aquatic ecosystems by synchronous ecological restoration

Ecosystem degradation and biodiversity loss have been caused by economic booms in developing countries over recent decades. In response, ecosystem restoration projects have been advanced in some countries but the effectiveness of different approaches and indicators at large spatio-temporal scales (i.e., whole catchments) remains poorly understood. This study assessed the effectiveness of a diverse array of 440 aquatic restoration projects including wastewater treatment, constructed wetlands, plant/algae salvage and dredging of contaminated sediments implemented and maintained from 2007 to 2017 across more than 2000 km² of the northwest Taihu basin (Yixing, China). Synchronized investigations of water quality and invertebrate communities were conducted before and after restoration. Our analysis showed that even though there was rapid urbanization at this time, nutrient concentrations (NH₄⁺-N, TN, TP) and biological indices of benthic invertebrate (taxonomic richness, Shannon diversity, sensitive taxon density) improved significantly across most of the study area. Improvements were associated with the type of restoration project, with projects targeting pollution-sources leading to the clearest ecosystem responses compared with those remediating pollution sinks. However, in some locations, the recovery of biotic communities appears to lag behind nutrients (e.g., nitrogen and phosphorus), likely reflecting long-distance re-colonization routes for invertebrates given the level of pre-restoration degradation of the catchment. Overall, the study suggests that ecological damage caused by recent rapid economic development in China could potentially be mitigated by massive restoration investments synchronized across whole catchments, although these effects could be expected to be enhanced if urbanization rates were reduced at the same time.

Mapping Land Use/Cover Dynamics of the Yellow River Basin from 1986 to 2018 Supported by Google Earth Engine

Changes in the land use/cover alter the Earth system processes and affect the provision of ecosystem services, posing a challenge to achieve sustainable development. In the past few decades, the Yellow River (YR) basin faced enormous social and environmental sustainability challenges associated with environmental degradation, soil erosion, vegetation restoration, and economic development, which makes it important to understand the long-term land use/cover dynamics of this region. Here, using three decades of Landsat imagery (17,080 images) and incorporating physiography data, we developed an effective annual land use/cover mapping framework and provided a set of 90 m resolution continuous annual land use/cover maps of the YR basin from 1986 to 2018 based on the Google Earth Engine and the Classification and Regression Trees algorithm. The independent random sampling validations based on the field surveys (640 points) and Google Earth (3456 points) indicated that the overall accuracy of these maps is 78.3% and 80.0%, respectively. The analysis of the land system of the YR basin showed that this region presents complex temporal and spatial changes, and the main change patterns include no change or little change, cropland loss and urban expansion, grassland restoration, increase in orchard and terrace, and increase in forest during the entire study period. The major land use/cover change has occurred in the transitions from forests, grasslands, and croplands to the class of orchard and terrace (19.8% of all change area), which not only increase the greenness but also raised the income, suggesting that YR progress towards sustainable development goals for livelihood security, economic growth, and ecological protection. Based on these data and analysis, we can further understand the role of the land system in the mutual feedback between society and the environment, and provide support for ecological conservation, high-quality development, and the formulation of sustainable management policies in this basin, highlighting the importance of continuous land use/cover information for understanding the interactions between the human and natural systems.

Spatiotemporal Patterns of Ecosystem Restoration Activities and Their Effects on Changes in Terrestrial Gross Primary Production in Southwest China

Large-scale ecosystem restoration projects (ERPs) have been implemented since the beginning of the new millennium to restore vegetation and improve the ecosystem in Southwest China. However, quantifying the effects of specific restoration activities, such as afforestation and grass planting, on vegetation recovery is difficult due to their incommensurable spatiotemporal distribution. Long-term and successive ERP-driven land use/cover changes (LUCCs) were used to recognise the spatiotemporal patterns of major restoration activities, and a contribution index was defined to assess the effects of these activities on gross primary production (GPP) dynamics in Southwest China during the period of 2001–2015. The results were as follows. (1) Afforestation and grass planting were major restoration activities that accounted for more than 54% of all LUCCs in Southwest China. Approximately 96% of restoration activities involved afforestation, and these activities were mostly distributed around Yunnan Province. (2) The Breathing Earth System Simulator (BESS) GPP performed better than the Moderate Resolution Imaging Spectroradiometer (MODIS) GPP validated by field observation data. Nevertheless, their annual GPP trends were similar and increased by 12,581 g C m−2 d−1 and 13,406 g C m−2 d−1 for MODIS and BESS GPPs, respectively. (3) Although the afforestation and grass planting areas accounted for less than 1% of the total area of Southwest China, they contributed to more than 1% of the annual GPP increase in the entire study area. Afforestation directly contributed 14.94% (BESS GPP) or 24.64% (MODIS GPP) to the annual GPP increase. Meanwhile, grass planting directly contributed only 0.41% (BESS GPP) or 0.03% (MODIS GPP) to the annual GPP increase.

Quantifying the Effects of Vegetation Restorations on the Soil Erosion Export and Nutrient Loss on the Loess Plateau

The transport of eroded soil to rivers changes the nutrient cycles of river ecosystems and has significant impacts on the regional eco-environment and human health. The Loess Plateau, a leading vegetation restoration region in China and the world, has experienced severe soil erosion and nutrient loss, however, the extent to which vegetation restoration prevents soil erosion export (to rivers) and it caused nutrient loss is unknown. To evaluate the effects of the first stage of the Grain for Green Project (GFGP) on the Loess Plateau (started in 1999 and ended in 2013), we analyzed the vegetation change trends and quantified the effects of GFGP on soil erosion export (to rivers) and it caused nutrient loss by considering soil erosion processes. The results were as follows: (1) in the first half of study period (from 1982 to 1998), the vegetation cover changed little, but after the implementation of the first stage of the GFGP (from 1999 to 2013), the vegetation cover of 75.0% of the study area showed a significant increase; (2) The proportion of eroded areas decreased from 41.8 to 26.7% as a result of the GFGP, and the erosion intensity lessened in most regions; the implementation significantly reduce the soil nutrient loss; (3) at the county level, soil erosion export could be avoided significantly by the increasing of vegetation greenness in the study area (R = -0.49). These results illustrate the relationships among changes in vegetation cover, soil erosion and nutrient export, which could provide a reference for local government for making ecology-relative policies.

Quantitatively assessing the effects of climate change and human activities on ecosystem degradation and restoration in southwest China

Identifying the effects of climate change and human activities on the degradation and restoration of terrestrial ecosystems is essential for sustainable management of these ecosystems. However, our knowledge of methodology on this topic is limited. To assess the relative contribution of climate change and human activities, actual and potential net primary productivity (NPPa and NPPp respectively), and human appropriation of net primary productivity (HANPP) were calculated and applied to the monitoring of forest, grassland, and cropland ecosystems in Yunnan–Guizhou–Sichuan Provinces, southwest China. We determined annual means of 476 g C m–2 year–1 for NPPa, 1314 g C m–2 year–1 for NPPp, and 849 g C m–2 year–1 for HANPP during the period between 2007 and 2016. Furthermore, the area with an increasing NPPa accounted for 75.12% of the total area of the three ecosystems. Similarly, the areas with increasing NPPp and HANPP accounted for 77.60 and 57.58% of the study area respectively. Furthermore, we found that ~57.58% of areas with ecosystem restored was due to climate change, 23.39% due to human activities, and 19.03% due to the combined effects of human activities and climate change. In contrast, climate change and human activities contributed to 19.47 and 76.36%, respectively, of the areas of degraded ecosystem. Only 4.17% of degraded ecosystem could be attributed to the combined influences of climate change and human activities. We conclude that human activities were mainly responsible for ecosystem degradation, whereas climate change benefitted ecosystem restoration in southwest China in the past decade.