Acarlar Wetland

Acarlar Marsh is a swamp forest ecosystem located in northwestern Türkiye, between the districts of Karasu and Karasu and Kaynarca in Sakarya province. It covers an area of 1,562 hectares. Its length is approximately 7.5 kilometers and its width varies between 250 and 1,250 meters. Its depth reaches up to 1.5 meters.

As the largest single-piece swamp forest in Türkiye, Acarlar Marsh is notable for both its ecological diversity and geomorphological features. Located 6 kilometers west of the Sakarya River, the marsh drains its excess water into the Sakarya River via the Okçu Creek.

^{Acarlar Longozu.} (TC.Kültür ve Turizm Bakanlığı)

Acarlar Marsh is situated near the Black Sea coast, bordered by sand dunes 20–25 meters high to the north and low hills averaging 100 meters in elevation to the south. The marsh exhibits characteristics of a coastal barrier lake. This ecosystem formed over time through the accumulation of alluvial sediments carried by the Sakarya River and lagoons created by waves from the Black Sea.

Tree species common in Acarlar Marsh include hornbeam, alder, oak, and black poplar. Much of the area is surrounded by hornbeam forests that can remain submerged seasonally. These forested areas adapt to seasonal fluctuations in water levels.

Approximately 2,300 plant species are found in the marsh. The water violet (Hottonia palustris) is an endemic species found only in this region. Numerous rare aquatic plants are also present, including the summer snowflake (Leucojum aestivum) and water lilies in yellow, white, and purple colors.

Acarlar Marsh lies along a migratory bird route and provides habitat for 180 bird species, 147 of which are protected. Species observed in the area include the mute swan, grebe, and wild duck. Among terrestrial fauna, mammals such as rabbit, fox, wild boar, badger, eagle, and squirrel are common.

Freshwater fishing is practiced in the marsh, with fish species such as roach, roach, carp, pike, and perch inhabiting its waters. Local communities also trade medicinal plants such as the water onion.

^{Acarlar Longozu.}(TC.Kültür ve Turizm Bakanlığı)

Acarlar Marsh was declared a First-Degree Natural Site by the Bursa Council for the Protection of Cultural and Natural Heritage in 1998. In 2009, it was also registered as a Wetland. As the only Wildlife Development Area in Sakarya, the marsh has been the subject of various planning initiatives aimed at conserving biodiversity and promoting sustainable use.

In 1971, the Adapazarı Soil and Water Organization widened the Okçu Creek, the marsh’s natural outlet, converting it into a canal. As a result of this intervention, approximately 40 percent of the lake area was reduced.

During summer months, when water levels recede, exposed areas are used by local communities for agriculture. Infrastructure including walking paths, restaurants, picnic and park areas, as well as boat and water bike tours has been developed on the Karasu side of the marsh to promote eco-tourism.

A 750-meter-long boardwalk has been constructed for visitors. The area is favored for birdwatching, plant observation, and nature photography.

^{Acarlar Longozu.}(TC.Kültür ve Turizm Bakanlığı)

Villages surrounding Acarlar Marsh include Denizköy, Karamüezzinler, Üçoluk, Taşlıgeçit, and Camitepe in the Karasu district, and Turnalı, Büyükyanık, and Birlikköy in the Kaynarca district. The marsh is approximately 50 kilometers from the center of Sakarya province and about 26 kilometers from Karasu district.