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Geographical description

Territory: Mayotte

Town: Tsingoni

Altitude: 1,355 feet

Surface area: 21 protected acres (lake and its shoreline).

Connection to the hydrographic network, hydrology and seasonality

Lake Karihani, (or Karehani), also known as “Dziani Kariani” in Shimaore, is located in a hollow; the water filling this natural lake mainly originates from runoff water. There is no river. Water supply occurs via infiltration/percolation from the surrounding mountainsides. This is why the water level is extremely variable: ranging from just a few inches to 8 ft. depending on the season and year. During the rainy season it can extend up to 7 acres in surface area, and sometimes dries out completely at the end of the dry season (between October and December).

Flora and Fauna

Fauna

The fauna is rich and varied. Indeed, the lake is home to a wide variety of bird species. It was actually the moorhens, locally known as “Kariha” in Shimaore, that gave their name to the site. Over 57 bird species have been recorded (© database Gepomay). This makes it the site with the largest bird community on the island.

Aquatic birds, such as little grebes and moorhens, or even Allen’s gallinules, rely on the site to build their nests, and remain there year-round. During the rainy season, the lake is a refuge for certain species of egrets and herons. The Malagasy pond heron (most endangered bird in Mayotte) can be seen there all year, as it feeds directly on-site.

Shorebirds, small wading birds and large migrating birds find refuge there during hibernation, or simply have a break there before pursuing their migration – such as the Madagascan pratincole, which arrives between August and September, or the common greenshanks, wood sandpipers or common sandpipers.

Other birds also come to the lake’s shorelines, that are less dependent on the site and live solely on dry land. This is the case for three of the island’s endemic species: the Mayotte sunbird, the Mayotte drongo and the Mayotte scops owl.

 

Great egret & Little grebe

 

This freshwater wetland is also home to a number of dragonflies and amphibians, such as frogs and tree frogs – that serve as delicious meals for birds during the dry season when the lake is shallower.

A number of Mayotte’s emblematic mammals can also be found there, such as the maki (sub-species of the endemic Lemur fulvus mayottensis) and fruit bat, as well as harmless reptiles such as the Mayotte grass snake or the spotted tree snake. Lastly, variants of the marbled eel species have also been spotted, swimming up from the sea via the Ourouvéni River.

The list of invertebrates is far from being complete, but odonate- and lepidoptera-lovers will no doubt find the site interesting.

 

Flora

The Dziani Kariani’s aquatic flora is mainly made up of purple-flowered water lilies and duckweeds.

The flora growing on the lake and its shoreline is made up of species that are relatively common in the Indian Ocean or pan-tropical region, as the area was vastly anthropized by farmers and most importantly as pastoralism is still very present. The presence of Leersia perieri – a type of grass discovered in 2005 around the lake and until then only recorded in Madagascar – should nonetheless be noted. This species is in fact protected.

The north-eastern side of the lake is colonized by a ring of giant brambles – a highly invasive plant in Mayotte’s wetlands. It is in fact the second cause of site deterioration after land filling.

Lastly, the plants growing on the banks of Lake Karihani are actually the remnants of cinnamon and ylang-ylang plantations, and of agro-forest trees: jack trees, mango trees, citrus trees, breadfruit, etc.

Protection and recognition

Since 1997, the Dziani Kariani has been protected by the Conservatoire du littoral. In 2007, a management plan was instated, and its implementation was entrusted to Mayotte’s departmental council.

Conservatoire du littoral            logo mayotte

Issues, production, usage, and pressure

The Dziani Kariani’s water zebu

Several livestock farmers use the body of water as a watering hole for their zebus, and the lake’s shores are used as pastureland. The water trampling and animal feces increase earth suspension in the water, the number of bird nests destroyed and the amount of organic matter present in the water. Therefore, properly preserving this site means monitoring livestock farming practices, and a project aiming for the installation of drinking troughs is currently being defined to prevent the zebus from drinking straight from the lake.

Invasive species

Imported from Reunion by a Coconi-based farmer in the 1980s, with a view to creating impassable hedges, the giant brambles quickly spread to the heart of the island’s wetlands, due to the unfortunately passive attitude of the forest and agriculture services at the time, even though the species was already well-known by specialists.

Lantana camara, although less aggressive in dry areas, has also caused great suffocation and allelopathy issues, which have limited the re-invasion of abandoned land by indigenous plants.

Lastly, most agricultural species and their associated pan-tropical ruderals also complicate the site’s restoration. This is the case for the African tulip tree, ylang-ylang plants, mango trees and coconut trees.

Little by little, non-native species are replaced by local species better suited to the site, such as erythrina, tacamahac-tree and raffia palms.

Deforestation

The mountainsides surrounding Lake Karihani are also affected by regular tree clearing. The lake’s surrounding mountainsides that lie outside the protected scope are those most affected.

Lake filling

Another problem relating to this site concerns the filling and the drying-out of the lake, significantly changing the downstream catchment area’s hydrographic situation.

History

The Dziani Karihani’s surrounding mountainsides were vast forestland during the 19th century, and supplied neighboring sugar refineries with firewood. Imported from Africa, the African tulip tree is easily recognizable thanks to its red-orange flowers in the shape of tulips. It is currently one of the widely planted species that poses a threat to the local flora because of its invasive nature.

Following the decline of the sugar industry, the lake’s mountainsides were wooded by Comores Bambao until 1975. The African tulip tree was gradually replaced with advantageous species such as ylang-ylang and cinnamon. When visiting the site, all these species can still be seen, and you many even smell the enchanting scent of ylang if you wait until nightfall.

Discover the site

You can walk around the lake path in about 50 minutes.

An observatory, built along the shoreline by the Conservatoire du littoral and Mayotte’s departmental council, enables visitors to watch the birds without disturbing them.