Observed impacts of large wind farms on grassland carbon cycling

Impact pathways of wind farms on grassland carbon and water cycles

In recent years, with the rapid development of the wind power industry, the ecological impacts of wind farms (WFs) have received increasing attention. Although previous studies have shown that WFs can affect various ecosystem indicators, the specific pathways of these impacts remain unclear. In this context, we analyzed the impact pathways of 139 grassland WFs located in Inner Mongolia on carbon‒water fluxes during the growing season via multisource satellite data from 2004 to 2020. The results revealed that WFs have a significant impact on gross primary productivity (GPP) and evapotranspiration (ET) at the regional scale. Specifically, WFs influence the vapor pressure deficit (VPD) by altering both the daytime and nighttime land surface temperature (LST) and further influence the GPP and ET through the VPD. Moreover, changes in the daytime LST induced by WFs also impact soil moisture, which further influences GPP. Compared with previous studies, we propose a method based on ridge regression and hypothesis testing to identify the mediating variables of WFs' impact on carbon and water fluxes. Furthermore, after controlling for grazing interference, we quantitatively analyze the complete pathways by which WFs impact carbon and water fluxes, rather than relying solely on qualitative speculation and discussion. This study revealed the cascading effects of WF ecological impacts, deepened the understanding of WF influences, and offered new directions for future research.

Floating photovoltaics strongly reduce water temperature: A whole-lake experiment

Floating photovoltaics (FPVs), solar panels installed on floating structures in freshwater ecosystems such as lakes, represent a growing renewable technology aimed at decarbonizing the energy sector. However, robust empirical assessments of its environmental effects are still lacking. We used a Before-After-Control-Impact design replicated at the ecosystem level (n = 6 lakes: three lakes with FPV compared to three non-FPV lakes) to determine the global effects of FPV on water temperature over three years and allowing to isolate FPV effects from natural variability. Overall, we found that the presence of FPV strongly decreased annual water temperature (1.2 °C on average). The reduction in water temperature induced by FPV increased significantly with air temperature and differed between seasons, with stronger reductions (up to 3 °C) observed during warmest days of the year in spring and summer. In addition, the reduction in water temperature also occurred in areas of the lakes that were not covered by FPV. In the context of climate warming, decreased water temperature in summer could benefit freshwater organisms but these benefits could be counterbalanced by other negative impacts such as decreases in dissolved oxygen and modifications in the C cycle, including greenhouse gas emissions. Therefore, the cascading effects of FPV on freshwater biodiversity and ecosystem functioning still need to be assessed.

Immediate Effect of Floating Solar Energy Deployment on Greenhouse Gas Dynamics in Ponds

Floating photovoltaic (FPV) solar energy offers promise for renewable electricity production that spares land for other societal benefits. FPV deployment may alter greenhouse gas (GHG) production and emissions from waterbodies by changing physical, chemical, and biological processes, which can have implications for the carbon cost of energy production with FPV. Here, we use an ecosystem-scale experiment to assess how GHG dynamics in ponds respond to installation of operationally representative FPV. Following FPV deployments of 70% array coverage, daily whole-pond GHG emissions increased by 26.8% on a carbon dioxide-equivalent (CO2-eq) basis, and dissolved oxygen availability rapidly decreased. Despite increased emissions following FPV deployment, FPV-derived GHG emissions from waterbodies are likely lower than landscape GHG emissions associated with terrestrial solar and hydropower production on a CO2-eq kWh-1 basis. Adaptive management strategies like bubbler installation may reduce the magnitude of FPV impacts on GHG and dissolved oxygen dynamics.

Comprehensive assessment of the climatic and vegetation impacts of wind farms on grasslands: A case study in inner Mongolia, China

Although wind power contributes to the reduction of greenhouse gas emissions, it also has significant impacts on the local climate and vegetation. Exploring these impacts is important for the sustainable development of wind power. Therefore, based on moderate-resolution imaging spectroradiometer (MODIS) data and other remote sensing data from 2003 to 2022, this paper investigated the impacts of 101 grassland wind farms (WFs) in Inner Mongolia on land-atmosphere water and heat exchange, vegetation growth, ecosystem primary productivity, and vegetation structural characteristics during the growing season and revealed the spatial distribution patterns of the impacts of WFs as well as differences between different types of grasslands. The results indicated that WFs increased the nighttime land surface temperature (LST), decreased evapotranspiration (ET), inhibited vegetation growth, decreased gross primary productivity (GPP), and reduced the leaf area index (LAI) in growing season grasslands. This effect varied across different types of grasslands and showed significant complexity. In terms of land-atmosphere water and heat exchange, nighttime LST increases and ET decreases were significant in the typical steppe but not in the meadow steppe. In terms of vegetation change, meadow steppe had the most inhibited vegetation growth and the greatest reduction in GPP. In terms of the impact range, WFs on typical steppe and meadow steppe have opposite effects on vegetation growth and ecosystem primary productivity inside and outside of them, i.e., they inhibit vegetation growth and reduce GPP inside the WF areas but promote vegetation growth and increase GPP outside the WF areas. Compared with previous studies, this study analyzed multiple climate and vegetation indicators based on many WF samples, which reduced the uncertainty associated with a single sample and provided more comprehensive and comparable observations of different types of grasslands. These findings can help to balance the relationship between wind power development and ecological protection.

Uppermost global tree elevations are primarily limited by low temperature or insufficient moisture

The impact of anthropogenic global warming has induced significant upward dispersal of trees to higher elevations at alpine treelines. Assessing vertical deviation from current uppermost tree distributions to potential treeline positions is crucial for understanding ecosystem responses to evolving global climate. However, due to data resolution constraints and research scale limitation, comprehending the global pattern of alpine treeline elevations and driving factors remains challenging. This study constructed a comprehensive quasi-observational dataset of uppermost tree distribution across global mountains using Google Earth imagery. Validating the isotherm of mean growing-season air temperature at 6.6 ± 0.3°C as the global indicator of thermal treeline, we found that around two-thirds of uppermost tree distribution records significantly deviated from it. Drought conditions constitute the primary driver in 51% of cases, followed by mountain elevation effect which indicates surface heat (27%). Our analyses underscore the multifaceted determinants of global patterns of alpine treeline, explaining divergent treeline responses to climate warming. Moisture, along with temperature and disturbance, plays the most fundamental roles in understanding global variation of alpine treeline elevation and forecasting alpine treeline response to ongoing global warming.