Azov-type spits: long-term monitoring of morphodynamics and vegetation in response to changing environment

Azov-type spits (ATS) are unique landforms located along the Northern coast of the Sea of Azov (NA) that have no global analogs. They play a vital role in delivering essential ecosystem services and significantly contribute to the economy of southern Ukraine. ATS are highly sensitive and dynamically responsive to environmental changes, including global and local climate changes, rising sea levels, geological shifts in the Ukrainian crystalline shield, internal shifts in the Sea of Azov and various anthropogenic influences. These factors significantly shape the ATS, influencing their capacity to accumulate biogenic material and sediments, thereby impacting vegetation cover, resilience and functioning within their ecological context.

Our study on ATS morphodynamics and vegetation changes is based on a 95-year dataset that incorporates retrospective vegetation maps (1927-1929, 1934, 1996-1999), grassland releves (1995-1999) and satellite imagery (1975-2022) using specific standardized indices (NDVI, NDWI, NDMI, Thermal). We employed Earth Remote Sensing (ERS) tools due to the impracticality of field research amid the ongoing military occupation of ATS territories. Climate change vulnerability was assessed by examining surface air temperature and precipitation changes for the periods 1900-2021 and 1991-2021.

Meteorological data for NA shows a consistent climate change trend, including rising annual surface temperatures (1.14 ± 0.3 °C/100 years) and increased annual precipitation (98 ± 35 mm/100 years) over the last 120 years. Recent decades have witnessed intensified aridization, with up to a 15% drop in precipitation and a 0.8 °C per decade temperature increase, accompanied by increased evaporation. Our study reveals the ongoing transformation of ATS and their vegetation, primarily driven by inundation, aggravated by climate change and rising sea levels. ERS tools demonstrated their effectiveness in monitoring environmental changes under challenging circumstances, identifying general trends in the state of plant communities and validating our earlier forecasts for changes in vegetation cover. The increase in the area of halophytic meadow and marsh plant communities occurred alongside a certain decrease in their productivity, while the reduction in sandy-steppe plant community areas was accompanied by an increase in their productivity. The study provides a complex evaluation of the current anthropogenic impacts on the spits and their vegetation.