Impact of climate change factor on the resource (providing) ecosystem services of the Lower Danube wetlands

Abstract

Problem Statement. Wetlands perform many vital functions, in particular: accumulation and storage of surface waters; protection from storms and floods; strengthening the coastline and curbing water erosion; hydraulic connection with groundwater; surface water purification; nutrient content; deposit formation; pollutants retention; stabilization of local climatic conditions, especially the amount of precipitation and temperature of the near-surface layer of the atmosphere. They are the world's most productive ecosystems, focus of biodiversity, sources of water and primary productivity on which the existence of innumerable species of plants and animals depends. Wetlands support numerous species of birds, mammals, reptiles, amphibians, fish and invertebrates. The ecological character of wetlands is the totality of their ecosystem components, processes and services at one time or another. Wetland ecosystem services are understood as the benefits that people receive from these. These are providing services (water and food); regulatory services (regulation of floods, droughts, land degradation, etc.); supporting services (soil formation, nutrient cycling, photosynthesis, biodiversity); cultural services (cultural and entertainment, spiritual, religious and other intangible benefits). In Ukraine, there are 2417 wetlands with a total area of about 255 million hectares. Among them are 50 wetlands of international importance with a total area of about 734 thousand hectares, a significant proportion of which falls on the territory of the North-Western Black Sea region coastal zone.

The aim of this study is to determine the state, vulnerabilities and climate change impact on the ecosystem services of the «Chilia Branch» wetlands.

Research Methodology. To determine the periods of drought, the study used the Standardised Precipitation Evapotranspiration Index (SPEI) from April to October 1980-2023. The SPEI index was calculated at a point located in the southern part of the Danube Biosphere Reserve. The assessment of the state of the vegetation cover was carried out on the basis of the analysis of Normalized Difference Vegetation Index (NDVI) the period 2017-2023 at two sites (Ermakov Island and Limba Island). To analyze dynamics land cover in the wetland area, were used Sentinel-2 land use satellite imagery for the period 2017-2021.

Results. Analysis of the SPEI index showed that during the study period there was a positive statistically significant linear trend towards an increase in dry conditions (0.26 / 10 years). In the period 1980-2023 during the growing season on the territory of the "Chilia Branch" wetland, there is a change in weather conditions towards arid, which poses a certain threat. At the same time, it should be noted that the unique hydrological complex of the Danube Delta has a mitigating effect of the atmospheric drought impact on the vegetation. Also, it should be noted that the threat to coastal wetlands is the anthropogenic transformation of coastal natural systems (urbanization processes, expansion of land for agricultural needs, pollution of soil and surface waters), which can lead to loss of habitats of living organisms and deterioration of ecosystem services.