Year after year they come. Herds of African buffalo, red lechwe, hippopotamuses and wildebeests converge upon the heart of the Okavango Basin as it blossoms to life with the seasonal influx of rainwater from the Angolan highlands. The world’s largest population of elephants parade across desert terrain and into the Okavango Delta where their massive presence literally carves channels through the marshy landscape as they traverse the refreshing waters of the delta.
Located in northwest Botswana, the Okavango Delta is one of Africa’s richest places for biodiversity. In addition to supporting the world’s largest population of elephants (around 130,000), it sustains robust populations of some of the world’s most endangered large mammals such as cheetahs, white and black rhinoceroses, wild dogs and lions. The delta’s health is dependent on the source lakes and rivers in Angola’s highlands that are inundated by seasonal rains propelling them to flow and converge through Namibia into Botswana.
Like the animals that instinctively return every year to bask in the delta’s seasonal deluge, the National Geographic Okavango Wilderness Project (NGOWP) expedition team set off on their annual pilgrimage transecting the delta. They will travel a new course this year using the Nqoga, Maunachira, Mboroga, Santantadibe and Thamalakane channel systems in the northern Okavango Delta.
For both our team and the countless wildlife that migrate to this life-sustaining region, their journey may be one of new challenges. The seasonal rains of the Angolan highlands were well below average this year and flood levels this low have not been seen in 40 to 50 years.
By mid-February, it became clear to the NGOWP team that the delta was not going to receive floodwaters this year. This means that the team’s primary method of travel, by traditional mokoro canoes, may become untenable for large tracts of their annual trek through the delta.
In anticipation of the challenging trek, the team completed fixed-wing and helicopter surveys to plan the best routes. During these flights, they witnessed not only the greatly diminished water levels and completely dried up riverbeds, like the Thamalakane River, they also observed large human-set fires burning out of control over dry floodplains, papyri and reedbeds. Due to the failure of the rains this year, these fires had been burning throughout the “rainy” season.
Human-set fires represent one of the greatest threats to the source waters, and these drier conditions, unsurprisingly, only exacerbate their effects. While the Okavango watershed’s landscape is naturally adapted to a high frequency of fires, extensive burning can severely impact even such resilient habitats. Fire is widespread in the landscape, particularly along the rivers and floodplains, where it is used for slash-and-burn agriculture and charcoal production as well as hunting.
Intentionally set and accidental large-scale burning results in the loss of miombo woodlands and riverine forests. Continued loss of the woodlands that surround the source lakes and rivers in Angola will ultimately result in most of the rainwater being lost into the deep sands of the Kalahari Desert, leaving the rivers and source lakes to dry up seasonally, peat deposits to dry up and potentially burn, and vast quantities of carbon to be released into the atmosphere.
This year’s low water levels and the observance of uncontrolled fires consuming a drier, more fuel-rich landscape, are a dire warning of what the future could hold for the Okavango Delta. Many climate models predict temperatures in southern Africa will continue to rise, and the number of heat-wave days and high fire-danger days will drastically increase while the soil-moisture availability is projected to decline.
The impacts of this low flood year have demonstrated that the area is not as resilient to climate change as many believed it to be, which is an important call to action to protect the Okavango-Zambezi Water Tower and keep its source waters free flowing.
The NGOWP is committed to gaining permanent protection for the source waters of the Okavango Delta and ensuring the entire region is sustainably managed for the future to benefit both the wildlife and the people that rely on it.
As a critical step toward meeting this goal, the NGOWP team has installed a monitoring station with sensors to capture flow rate and water quality sensor at Divundu on the Okavango River. After 12 months, this data set can be used as a baseline to calibrate all historical data to help us better understand the relative importance of the Cuito River (which supplies roughly 45% of the delta’s water) and its role in the Okavango-Zambezi Water Tower.
Capturing ecological baselines like this is crucial for understanding not only the dynamics of the system, but also for the management needs of the region and securing its future protection.