Effects of active and passive land use management after cropland abandonment on water and vegetation dynamics in the Central Spanish Pyrenees

Medium term hydrochemical and CO2 responses to anthropogenic and environmental changes in karst headwater streams

This study investigates the intricate effects of lithology, temperature, discharge, and land use changes on headwater stream chemistry by analysing two decades of hydrochemical data from twenty karst headwater catchments in the Garonne River basin, France. Focused on the Pyrenees and the lowland (LM) and upland (UM) regions of the Massif Central, this study identified significant regional variations and commonalities in water chemistry. The headwater streams were clustered based on their hydrological and hydrochemical profiles, revealing strong similarities between upland sites, i.e. UM and Pyrenees, despite their geographical distance. The findings revealed a predominance of water driven by calcite dissolution, with specific influences from minor lithologies. Seasonal variations in water chemistry were primarily driven by hydrological conditions. Trend analyses highlighted increased pCO2 concentration in both the Pyrenees and UM, linked to higher forest density and agricultural activities, respectively. In contrast, LM exhibited increasing Ca2+ and HCO3- concentrations alongside decreasing trends in pCO2 and discharge, and increased nitrate concentration. While overall water temperatures increase, only a few sites exhibited significant warming trends, consistent with similar studies in the region and worldwide. These findings underscore the complex interplay between land use changes and hydrochemical dynamics in karst headwaters. They reveal that rising pCO2 concentration trends in upland regions are driven by reforestation and agricultural practices, which have significant implications in CO2 emissions, and consequently for regional and global carbon budgets and carbon-related policies. In lowland areas, declining water resources and increasing ion concentrations highlight potential challenges for water management, particularly in sensitive karst catchments. This study provides a baseline for understanding how karst headwaters respond to environmental changes. Expanding this research to other karst systems worldwide, under different climates, would help validate and model these findings, and improve our understanding of the global carbon cycle.

Shrub clearing and extensive livestock as a strategy for enhancing ecosystem services in degraded Mediterranean mid-mountain areas

Land abandonment in the Mediterranean mountains since the 20th century has led to a reduction of ecosystem services, due to revegetation and homogenization of the landscape. To counteract these effects, the regional administration of La Rioja in Spain initiated a Plan for Shrub Clearing (PSC) combined with extensive livestock grazing in 1986, which is still in action today. This study analyses the effects of pairing clearing with grazing in an experimental area of the Leza valley (Iberian System) on: (i) the landscape structure and structural diversity; (ii) the production of pasture; (iii) fire control; (iv) soil organic carbon sequestration (also considering soil environmental types); (v) surface water resources. The results show that: (i) a more fragmented landscape with greater diversity is created; (ii) grazing land is almost doubled in alkaline soils and four-fold in siliceous soils; (iii) fires are considerably reduced, with the mean surface fire spread falling from 34.1 ha/year from 1968 to 1985, to 1.2 ha/year between 1986 and 2022; (iv) regenerated post-clearance grazing soils sequester more organic carbon than that of shrublands, especially older clearings on alkaline soils (55.3 % more); (v) clearing increases hydrological connectivity and water resources. The conclusion is that managing the Mediterranean mid-mountains could be a very effective strategy to improve the supply of certain ecosystem services and improve the current socio-economic perspective of these marginal areas in a context of Global Change. The PSC also contributes to local development by increasing livestock numbers.

Russian-Ukrainian war impacts on the environment. Evidence from the field on soil properties and remote sensing

The Russian-Ukrainian war is having a dramatic impact on the environment. The effects are still unknown. However, it is expected that the effects will be substantial. Since the conflict is ongoing, it is challenging to have ground-accurate data that could show an idea of the extension of the impact. Remote sensing can support a preliminary analysis in areas without safety to conduct fieldwork. This work aims to assess the impacts of the Russian-Ukrainian war on the environment using field and remote sensing sources. This is the first work that published fieldwork data from this conflict. Different soil properties were studied (e.g., texture and heavy metals) in different places (Novy Korotych and Mala Rohan). Remote sensing (e.g., Normalised Difference Vegetation Index) at different spatial scales (Eastern Ukraine and case study in the Kharkiv region) were assessed between 2021 and 2022. The results showed that the finer sediments increased in bombed areas compared with not bombed ones. Also, there was an increase in the content of heavy metals (e.g., Manganese, Iron, Cobalt, Copper, Cadmium, Chromium, Lead and Nickel) in soils in the shelled areas, compared to the non-shelled. This was mainly observed in the Novy Korotych site. Remote sensing analysis revealed that between 2021 and 2022 at a large scale (Eastern and southeastern Ukraine), vegetation greenness decreased in the areas where the combats are more intense (Luhansk and Donetsk) and increased in the southern area (Zaporizhia and Kherson), likely due to agriculture abandonment. On a small scale (case study in Kharkiv region), the vegetation greenness was affected due to the bombing. Although our results are preliminary, it is important to highlight that shelling is increasing soil pollution and contributing to vegetation greenness reduction where the fighting is intense. The actual impacts of the war still need to be understood entirely.

Status, Trend, and Prospect of Global Farmland Abandonment Research: A Bibliometric Analysis

Farmland abandonment is one of the most important land use changes in the world today and crucial to the sustainable development of the global environment. The authors carried out extensive research on farmland abandonment from many perspectives, but, due to the variety of the research contents, rich research perspectives, and complex research objects, the current research in this field lacks comprehensiveness, objectivity, and systematization. In this study, the bibliometric R software packages bibliometrix and biblioshiny (K-Synth Srl, Naples, Italy) were used to analyze the development history and current situation of 896 articles on farmland abandonment in the Web of Science core collection database from 1980 to 2021, revealing their research hotspots and predicting the future development trends. Over the past 40 years, the number of published papers on abandoned farmland has continuously increased. Research mainly focused on the ecological environment, with natural succession, biodiversity, and vegetation restoration being high-frequency keywords in this field. Research on the social aspects of farmland abandonment has developed rapidly in the past 6 years. Based on these findings, this paper put forward four future research directions: the data source for the extraction of abandoned farmland should transform to high spatial-temporal resolution and hyperspectral remote sensing images; the method should pay more attention to the time series change detection and the application of the model; future research should focus on the economic costs of the reclamation of abandoned farmland and the ecological consequences of such reclamation; and the global ecological impact of vegetation succession after the abandonment of farmland should be further discussed from a broader perspective.

Combined effects of multi-land use decisions and climate change on water-related ecosystem services in Northeast China

Land use intensification and climate change have resulted in substantial changes in the provision of ecosystem services, particularly in China that experienced sharp increases in population growth and demands for goods and energy. To protect the environment and restore the degraded ecosystems, the Chinese government has implemented multiple national ecological restoration projects. Yet, the combined effects of climate change and land use and land cover change (LULCC) over large spatial scales that brace multiple land use decisions and great environmental heterogeneity remain unclear. We assessed the combined effects of LULCC and climate change on water-related ecosystem services (water provision and soil conservation services) from 1990s to 2020s in Northeast China using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. We found that water yield decreased by 9.78% and soil retention increased by 30.51% over the past 30 years. LULCC and climate change exerted negative effects on water yield whereas they both enhanced soil retention; LULCC interacted with climate change to have relatively small inhibitory effects on water yield and large facilitation effects on soil retention. Changes in water yield were mainly attributed to climate change, while soil retention was largely influenced by LULCC and its interaction with climate change. Our research highlights the importance of land use decisions and its interactive effects with climate change on ecosystem services in a heavily disturbed temperate region, and provides important information to inform future land management and policy making for sustaining diverse ecosystem services and ensuring human wellbeing.

Carbon sequestration and water yield tradeoffs following restoration of abandoned agricultural lands in Mediterranean mountains

Abandoned cropland areas have the potential to contribute to climate change mitigation through natural revegetation and afforestation programs. These programs increase above and belowground carbon sequestration by expanding forest cover. However, this potential to mitigate climate change often involves tradeoffs between carbon sequestration and water availability. Particularly in a water limited environments such as the Mediterranean region, any loss of recharge to groundwater or streamflow can have critical societal consequences. In this study, we used an ecohydrologic model, Regional Hydro-Ecological Simulation System (RHESSys), to quantify these tradeoffs for land management plans in abandoned cropland areas in Mediterranean mountains. Changes to Net Ecosystem Production (NEP), water yield and Water-Use Efficiency (WUE) under different land management and climate scenarios were estimated for Arnás, a catchment with similar geology, vegetation and climate to many of the locations targeted for land abandonment restoration in the Spanish Pyrenees. Results showed significant changes to both carbon and water fluxes related to land management, while changes related to a warming scenario were not significant. Afforestation scenarios showed the highest average annual carbon sequestration rates (112 g C·m^-2·yr^-1) but were also associated with the lowest water yield (runoff coefficient of 26%) and water use efficiency (1.4 g C·mm^-1) compared to natural revegetation (-27 g C·m^-2·yr^-1, 50%, 1.7 g C·mm^-1 respectively). Under both restoration scenarios, results showed that the catchment ecosystem is a carbon sink during mid-February to July, coinciding with peak monthly transpiration and WUE, while during the rest of the year the catchment ecosystem is a carbon source. These results contribute to understanding carbon and water tradeoffs in Mediterranean mountains and can help adapt restoration plans to address both carbon sequestration and water management objectives.

Impacts of Future Climate and Land Use/Cover Changes on Water-Related Ecosystem Services in Changbai Mountains, Northeast China

Sustaining ecosystem services in alpine regions is a pressing global challenge given future accelerating environmental changes. Understanding how future climate change and land use/cover change (LUCC) drive ecosystem service will be important in this challenge. However, few studies have considered the combined effects of future climate change and LUCC on ecosystem services. We assessed water yield and soil retention services and their drivers in the Changbai mountains region (CBMR) from the 2020 to 2050s using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and factor control experiments. Water yield decreased by 2.80% and soil retention increased by 6.14% over the 30 years. Climate change decreased water yield and increased soil retention, while LUCC decreased both water yield and soil retention. The interactive effects between climate change and LUCC had relatively small inhibitory effects on water yield and large facilitation effects on soil retention. Changes in water yield were mainly attributed to climate change, while soil retention was largely influenced by interaction. Our study highlights the individual and interactive contributions of future climate change and land use to ecosystem service in the mountains region, which can provide important information for informed future land management and policy making for sustaining diverse ecosystem services.

Unravelling Climate and Anthropogenic Forcings on the Evolution of Surface Water Resources in Southern France

In the Mediterranean, climate change and human pressures are expected to significantly impact the availability of surface water resources. In order to quantify these impacts during the last 60 years (1959–2018), we examined the hydro-climatic and land use change evolution in six coastal river basins of the Gulf of Lion in southern France. By combining observed water discharge, gridded climate, mapped land use and agricultural censuses data, we propose a statistical regression model which successfully reproduces the variability of annual water discharge in all basins. Our results clearly demonstrate that, despite important anthropogenic water withdrawals for irrigation, climate change is the major driver for the detected reduction of water discharge. The model can explain 78–88% of the variability of annual water discharge in the study catchments. It requires only two climatic indices that are solely computed from monthly temperature (T) and precipitation (P) data, thus allowing the estimation of the respective contributions of both parameters in the detected changes. According to our results, the study region experienced on average a warming trend of 1.6 °C during the last 60 years which alone was responsible for a reduction of almost 25% of surface water resources.

A Synopsis of Farmland Abandonment and Its Driving Factors in Nepal

Farmland abandonment is considered as an important phenomenon for changing eco-environmental and sociocultural landscapes of mountainous rural landscape. Many studies have analyzed farmland abandonment, its driving factors, geophysical processes and consequences at landscape: however, very few have focused on mountainous developing countries such as in Nepal, which is a rapidly urbanizing country suffering from serious farmland abandonment. Therefore, our study was an attempt to (i) assess the spatiotemporal extent of farmland abandonment in Nepal, (ii) explore driving factors of farmland abandonment, and (iii) discuss on the eco-environmental and sociocultural consequences in Nepal. We reviewed various literature, documents, and national reports to obtain a dataset pertaining to the overall status of farmland use and changes along with political and socioeconomic changes, economic development processes, and policy and governance in Nepal. Our results showed that farmland abandonment is widespread; however, it is more prevalent in the hilly and mountainous regions of Nepal. A total of 9,706,000 ha, accounting for 23.9% of the total cultivated farmland in Nepal, was abandoned during the period of 2001 to 2010. The driving factors included population growth, scattered distribution of settlements, urbanization, socio-economic development, poor access to physical services, and poor implementation of agriculture development policies. Furthermore, the increasing extent of natural disasters, malaria eradication, land reform and resettlement programs, the complex system of land ownership, land fragmentation, political instabilities, and the intensification of trading in agricultural products also acted as drivers of farmland abandonment in Nepal. Farmland abandonment generates negative effects on rural societies eco-environmentally and sociologically. Abandoned plots were subjected to different forms of geomorphic damage (e.g. landslide, debris flows, gully formation, sinkhole development etc.). Farmland landscape fragmented into a group of smaller interspersed patches. Such patches were opened for grassland. Furthermore, farmland abandonment also has effects on the local population and the whole society in terms of the production of goods (e.g., foods, feed, fiber), as well as services provided by the multi-functionality (e.g. sociocultural practices, values and norms) of the agricultural landscape. Therefore, this study plays an important role in planning and implementing eco-environmental management and social development processes in Nepal.