Wetlands are one of the most biologically productive ecosystems of the earth and consist of the subject of many studies. Wetlands, suitable feeding, breeding, and sheltering environments for many species and varieties, are accepted as natural wealth museums of the countries individually and the world. Moreover, wetlands, which have many economic services in the lives of the people living in their vicinity and the country, have a meaningful and different place among other ecosystems in terms of being essential carbon sinks and protecting the natural balance and biological diversity (Biler and Altındağ 2020).
Wetlands are an indispensable habitat for many flora and fauna species, especially migratory birds. These areas are vital for oxygen in the atmosphere to be produced and organic materials to dissolve. Wetlands have significant functions such as fishing, irrigation, drinking water supply, flood control, feeding the groundwater, and scientific, educational, aesthetic, archaeological, heritage, and historical benefits that are not intended for consumption (Bürgi et al. 2017). However, these areas are threatened by many human activities that cause habitat and species loss. Mainly, anthropogenic activities such as pollution, deterioration of water balance (underground water withdrawal, deterioration of natural drainage direction, changing the direction of surface water flow, holding surface water with dams and barriers, etc.), agricultural activities, drying, filling, waste storage, industrial and residential use are significant threats to wetlands (Bergstrom and Stoll 1993; Barbier 1993; Barbier et al. 1997; Turner et al. 2000; Sönmez & Somuncu, 2016; Biler, 2019; Biler and Altındağ 2020).
Researches reveal that wetland ecosystems, which share approximately 6% of the earth, are the most threatened areas among natural resources (Barbier et al. 1997). The destruction and loss of wetlands are appalling in almost every part of the world, especially in the Mediterranean countries. In France, there is a decrease of 10,000 ha every year. 60% of wetlands in Spain have been lost today. 80% of salty marshes in Portugal are under threat of disappearance. In Greece, 60% of the wetlands have been dried to obtain agricultural land. Wetlands have decreased by 28% in Tunisia in the last 100 years (Kence 2005; Korkanç 2005). Turkey has lost more than 50% (1,3 million ha) of wetlands throughout its history (Özesmi and Özesmi 1997; Korkanç 2005). Sultan Marshes are one of the most valuable among them, and it is trying to survive despite the problems it has been experiencing for years. Fig. 1 shows Sultan Marshes and the National Park, and Fig. 2 gives the wetland categories of the Sultan Marshes.
Sultan Marshes National Park is located 70 km south of Kayseri Province in the Central Anatolia Region, within Develi, Yeşilhisar, and Yahyalı Districts of Kayseri Province. Sultan Marshes National Park, which has an average altitude of 1071 m, is between 38° 12' 14" – 38° 25' 49" N latitudes and 35° 02' 20" – 35° 22' 20" E longitudes. The National Park area is 24,523 ha, and the total area, including the buffer zone, is 39,057 ha (Aksoy 2012).
Sultan Marshes are located in the center of the Develi Closed Basin with a catchment area of 319,000 km2. Erciyes Mountain, an extinct volcano with a height of 3,916 m, is in the northeast of the wetland. The area consists of fresh, salty, slightly salty lakes and swamp ecosystems. The main lakes are Yay Lake (3,650 km2, maximum depth 1.5 m, with two islands) and Çöl Lake (2,600 km2), which dries up heavily in summer. In its natural condition, Sultan Marshes are fed by Yahyalı, Develi, Ağcaşar and Yeşilhisar streams; Soysallı, Çayırözü and Yerköy springs and groundwater (Özesmi et al. 1993; Sönmez and Somuncu 2016; KTB 2021).
Develi Plain, where the Sultan Marshes are located, is in a closed basin. Therefore, Sultan Marshes is not a swamp but insurance that allows the ecosystem to live and prevents floods and overflows in the plain. Here, most of the protected area is owned and managed by the state. The local communities carry agricultural activities and reed cutting (Özesmi et al. 1993; KTB 2021).
Sultan Marshes National Park is a rare wetland habitat of international importance due to the coexistence of fresh and saltwater ecosystems. It is also critical due to its rich flora and fauna diversity (Aksoy 2012; Sönmez and Somuncu 2016).
In the Sultan Marshes, 11.6% (50 species) of the 430 natural plant species located within the steppe ecosystem are endemic. Especially, salty lakes are surrounded by sea cowpea (Salicornia) steppes. The swamps in the south consist mainly of Phragmites and Typha, Juncus, and Carex species (Aksoy 2012).
Among its fauna richness, bird species have the particular status for the Sultan Marshes because the marshes are located at the intersection of two significant bird migration routes passing through Turkey between Africa - Europe - Asia every year. Therefore, it has a vibrant species diversity as it provides different incubation, feeding, breeding, accommodation, and shelter. It is estimated that 600,000 water birds settled in the Sultan Marshes and their surroundings during the periods when the ecosystem features in the Marshes were close to perfect. According to the bird counting results, three hundred one bird species have been identified in Sultan Marshes (Özesmi et al. 1993; Turan et al. 1995; KTB 2021). Little cormorant, tawny heron, paddy egret, spoonbill, gray duck, summer duck, Hungarian duck, mottled duck, goose tail, crane, axilla, swamp swallow, maple plover, great plover, spur lapwing, laughing tern, little tern, and whiskered tern are among the valuable species. Angıt prefers the area in the summer, while many flamingos, cranes, and apricots use the area in the fall. Many waterfowl (130,000 species) are found in winter and during migration (KTB 2021).
The Marshes are essential for birds and the flora and fauna that feed and shelter them. Although it has not been thoroughly studied in the region, over 90 plankton species, 60 species of insects, 19 species of mollusks, ten species of reptiles, three species of amphibians, 21 species of mammals, and 174 plant species have been identified (Özesmi et al. 1993). Part of the marshes in the north (partly irrigated) has been converted into the grain, sugar beet, and sunflower fields. In addition, sheep are grazed in the surrounding steppes, and cattle are grazed in swampy areas (KTB 2021).
Sultan Marshes is one of the areas with the highest protection status in Turkey. In 1971, an area of 45,000 hectares in the region was reserved as a Wildlife Protection Area. An area of 17,200 hectares was given the status of Nature Protection Area in 1988 and the natural protected (SIT) area in 1993. In 1994, the 17,200 km2 area was selected as one of Turkey's first five Ramsar sites. In 2006, the protection status of the Sultan Marshes was changed and declared as a National Park. The last two statuses are based on the Nature Conservation Area borders, which do not include the Çöl Lake and most nearby steppes (Sönmez and Somuncu 2016; KTB 2021). In the 1950s, a part of the Kepir Marshes in the north was distributed to the villagers by the state. These 1,900 hectares of the Marshes, which are within the borders of the Nature Conservation Area, have been largely converted into agricultural land and pasture in the recent period. Today, a maximum of 500 hectares of the Marshes preserve their natural characteristics (KTB 2021).
There are many studies in the literature about the Sultan Marshes. Dadaser-Celik et al. (2008) demonstrated the change in Sultan Marshes between 1980-2003 with satellite images. The analysis showed that lake surface areas decreased by 93% from 1980 to 2003. Yay Lake was almost completely dry in 2003. The marshes receded more than 50%, and the surrounding steppe expanded into the lakes and marshes. Agriculture expanded in the western and eastern parts (Kepir Marshes) of the study area. Although the years 2000 and 2003 had lower than average annual precipitation and lower annual precipitation than in 1980 and 1987, the changes in Sultan Marshes are so significant that they cannot be solely attributed to weather fluctuations. According to the authors, surface water diversions, increased use of spring waters, and groundwater are responsible for the changes. Kesikoglu et al. (2019) focused on the changes from 2005 to 2012 in the Sultan Marshes. It was observed that marshes and steppe areas decreased while water and agricultural areas expanded from 2005 to 2012. These changes could be the results of water transfers to the marshes from the neighboring watershed.
Sultan Marshes wetland, a valuable Ramsar area in the arid, semi-arid region, is one of the areas in Turkey where the pressure of anthropogenic processes on wetlands can be observed most clearly. Therefore, it was chosen as the subject of study. This study aims to reveal the anthropogenic pressures on the Sultan Marshes the vulnerabilities of the wetland. In this study, land use/cover flows between 1990 and 2018 were evaluated in the Sultan Marshes, and these changes were analyzed together with other anthropogenic impacts. Considering Sultan Marshes and all wetlands under the same conditions, one of the terrifying facts today is that wetlands can be dragged into irreversible circumstances when the observed anthropogenic impacts are combined with climate change.