Okavango Delta-Oasis of the Kalahari
Okavango - Unique in Every Way
Located in the middle of arid desert lies the Okavango Delta; a lush wetland ecosystem. Unlike most deltas across the globe the Okavango doesn’t flow into the ocean, but instead flows into the Kalahari desert, making it one of the world’s few inland deltas. Unlike endorheic river systems which flow into basins forming lakes, inland deltas flow onto large flat plains, creating a mass expanse of wetlands. Littered with islands and channels, the Okavango is home to both large terrestrial animals, as well as numerous aquatic and bird species. It is a one of a kind ecosystem that should be protected.
Source of the Okavango
Due to its geographical location in the midst of arid shrub and desert, most of the Okavango’s water is lost to evapotranspiration. To feed this continual demand, water the Okavango river and its tributaries must provide the region with some 10 cubic kilometers of water per year, equivalent to 4 millions olympic swimming pools. The lion’s share of this water originates in the Angola highlands in central Angola. This mountainous region often receives over 1,200 millimeters of rainfall per year. The catchment area for the delta which includes the angolan highlands, covers an area of aproximately 171,000 km². Here, steep terrain and igneous rock in the catchment produce high run off rates, meaning that less water permeates soil and instead forms streams and rivers. These factors aid in forming the two major rivers; the Cubango and Cuito rivers which merge to form the Okavango river and eventually the delta. The timing of the arrival of the water in the delta is crucial to the ecosystem. The Okavango floods seasonally and its peak flooding period is between June and september. This coincides with the winter dry period meaning that just as food and water become scarce in the surrounding area, the Okavango springs to life. This makes it vital for animals in the adjacent wilderness areas which would not otherwise have adequate sources of food and water during this period.
The Okavango delta is home to a wide diversity of animals. Iconic African mammals such as elephants, lions, giraffes, cheetahs, leopards, and many more can be found here. Birds thrive as there is an abundance of both insects and fish. The abundance of fish and insects is also a staple food source for the delta’s many crocodiles and other reptiles. Each species plays a role in the ecosystem’s health.
Okavango is home to almost all the large African mammals. Most notable is its large population of African elephants: 20,000-25,000. This small area accounts for about 5% of the entire population of African elephants, making it the densest congregation of elephants on the planet. The major large herbivores in the Okavango delta are: elephants, cape buffalos, hippos, kudus, wildebeest, white and black rhinoceros, zebras and giraffes. All these herbivores have large and thriving populations in the Delta. The Okavango is also home to African predators including Lions, cheetahs, leopards, and the largest population of wild dogs found anywhere on earth. which at 500 accounts for 8% of the total world population. Some more unique species found in few places elsewhere are the lechwe and sitatunga; small deer-like animals which thrive in the aquatic environment of the Okavango. What makes the Okavango’s mammalian population unique is how dense it is. Due to the large quantity of water, it sustains some of the densest and most diverse large mammalian populations on the planet.
Home to over 500 species ranging from eagles to storks to hornbills, the Okavango delta is a haven for bird watchers. Most African species can be found, including African fish eagles, northern red hornbills, Malachite kingfishers and the Marabou storks. This high level of diversity is bolstered by the large number of migratory birds which spend the southern summer here.
Greater Kavango - Zambezi Conservation Area
Many people are familiar with great African parks like Serengeti or Kruger but the largest one of them, and perhaps the least well known is the Kavango Zambezi Transfrontier Conservation Area. This conservation area covers just over 500,000 square kilometers. This protected area is larger than the entirety of Thailand. As home to the many animals we described, it is a vital part of African conservation. For example about one quarter of all African bush elephants live here. This single contiguous area allows for animals to migrate naturally and creates a truly wild region, one of only a handful left on the planet.
Role as Carbon Sink
Wetlands are the best terrestrial carbon sinks on the planet, meaning that they act as storage for environmental CO2. However due to the Okavango being a very unique ecosystem, there appears to be a high degree of fluctuation in its role as a carbon sink. Some studies have found it to be an effective carbon sink while others have found it to be an overall CO2 emitter. Some researchers suggest that the Okavango changes between carbon sink and carbon source depending on many factors. The main factor is the hydrology of the ecosystem, specifically the volume of water and the area of land which it covers. The perennial flooded area (land which is flooded year round) according to one study was consistently a greenhouse gas source. The major carbon sink were the seasonally flooded regions of the ecosystem. However, this part of the ecosystem is very fragile and if water volume drops, as it did in 2019, a large area of seasonal wetlands severely dries up. This causes increased fires and general decay of vegetation, releasing significant CO2. This change from sink to source and back is compounded by the changing climate caused by human-induced climate change. Despite this variability, the system is believed to be a net carbon sink.
Threats to Ecosystem
To date the Okavango delta has been relatively mildly impacted by human activities but threats exist both locally and upstream. Local threats are poaching and habitat destruction. Fortunately due to stringent laws and protection, poaching has not been as large an issue as in other protected areas. The primary possible cause of future habitat destruction may be oil reserves. Already Reco Africa, a subsidiary of a Canadian mining company, has begun drilling upon some protected areas of the Okavango. If oil reserves are found it could likely lead to a conflict between protecting the environment or exploiting these reserves for the income they can generate. Upstream threats likely pose an even higher risk to the ecosystem. The first of these is reduced water in the major rivers feeding the Okavango. This could be caused by changing weather patterns due to climate change or by damming and increased agricultural land usage in the area. This could significantly reduce water, the lifeblood of the Okavango. Water pollution in the form of agricultural run-off also threatens the system with eutrophication which would lead to deadly algal blooms. Mining upstream could lead to heavy metals entering the delta which would be passed through the food chain and kill or sicken many animals.
As depressing as these threatening scenarios sound,the current threat level is not great, thanks to the environmental protection that applies in both Okavango and the greated Kavango - Zambezi area. The Okavango has some of the best environmental protection of any wetland, so far with minimal encroachment of land from agriculture, mining or development. This is due to several factors: the first is the low population density of the region which reduces demand for agricultural land. The second is strong institutions and a high HDI (human development index). Many less developed nations can claim that an area of land is protected but do not have the funds to adequately enforce this protection. Botswana does have the resources and means to protect these ecosystems, as it has the high levels of economic development and governance. These factors have helped reduce environmental pressures on the park and hopefully can allow it to maintain its good condition.
Almost all National parks in Africa have serious poaching issues. However, the Okavango fares far better than most. The two animals most at risk of poaching are elephants and rhinos. Elephants are poached for their ivory tusks which are used to make ornaments. Rhino horns are often used in traditional medicine in South East Asia and China despite zero proof of medicinal benefits. Both products are in very high demand and are very lucrative. A single rhino horn can fetch around 150,000 USD on the black market. Due to the pandemic, poaching has become a very serious issue as communities who cannot rely on tourism income turn to poaching. However in Botswana, where poaching has been on the rise in the past few years, the elephant population is thriving (unlike neighboring populations just north of Botswana). The number of animals killed each year is far lower than the current replacement rate. However, rhino poaching is quite severe. In Botswana, 60 rhinos were killed in the previous two years. This has caused Botswana to re-arm rangers in an attempt to enforce its zero tolerance on poaching while more enforcement is still needed to reduce poaching levels, especially for rhinos.
Like most national parks in Botswana Okavango tourism is low density and high end of the market. By utilizing this business model both the environment and local communities can benefit. Tourism specifically in the Okavango is centered around luxury lodges which provide safari’s for the guests. On top of typical vehicular safaris, some lodges offer boat and even horseback safaris. Due to the delta’s many channels, flat bottom boats are a great way to see the ecosystem. This model of high end ecotourism benefits local communities through employment as well as the environment, which is minimally impacted. In this way, economic incentives to preserve ecologically important areas are instilled.
Situated in one of the largest ecologically protected areas in Africa, the Okavango is a one of a kind wetland ecosystem. Home to both Africa's most iconic animals and some of its most endangered, the Okavango provides an excellent example of the role of ecosystems as both wildlife sanctuaries and carbon sinks. To continue to thrive, it will need the continued support of local communities, national leaders and responsible tourists.
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