MAUN: The Okavango Delta, a UNESCO World Heritage Site and one of the world’s most iconic ecosystems, is under threat.
This vast inland delta is a lifeline for countless species and a cornerstone of the region’s biodiversity, but scientists are saying the unique ecosystem is being disrupted by several threats mainly originating in its catchment areas, in Angola and Namibia.
With over 50 research expeditions throughout the Okavango basin’s major rivers and having supervised over 50 research papers about the system, the National Geographic Okavango Wilderness Project (NGOWP) Research Director, Dr Rainer von Brandis recently spelt out the mounting threats that could end the magic of the Okavango Delta – the country’s major tourist attraction.
Von Brandis was presenting ‘a Holistic View of the Okavango Basin: Hydrology, Biodiversity, and Human Impacts’, at the Okavango Conservation Science Symposium in Maun, organised by Nkashi Trust.
Von Brandis says climate change is perhaps the most pervasive threat to the Okavango Delta. Scientists agree that the climate historical data shows the rising temperatures and shifting rainfall patterns that are changing the system’s hydrological cycle and reducing the amount of water reaching the Delta.
The loss of peatlands in the Angolan Highlands water tower, which is the catchment of the Okavango Delta also poses a serious threat to the hydrology of the entire system according to von Brandis. The peatlands of the Angolan Highlands Water Tower (AHWT) have been described as the “glaciers of the Okavango”. This is because these peatlands are the sponges that hold the water and slowly release to the river ensuring a relatively constant flow throughout the season.
“The peat of the AHWT can absorb and retain up to five times its weight in water,” said von Brandis.
“Without these peatlands water will just rush down and the river will dry quickly and so the peat offers a sustained water flow”.
Von Brandis said this natural water retention phenomenon may become disrupted due to over-burning of peatlands. Over-burning, often caused by human activities, is becoming a significant problem both in the catchment area as well as downstream at Mohembo along the panhandle. In the catchment, excessive fires are causing soil erosion and increasing sediment loads in the rivers. The vegetation that stabilises the riverbanks are getting destroyed, and this would ultimately affect the river.
At the panhandle, over-burning is killing the papyrus that von Brandis calls, “the kidney of the Okavango”. He explains that the papyrus along the panhandle is responsible for cleaning the water before reaching the Delta. It is a natural sieve that traps all the undesirables coming with the river from upstream. And so, without papyrus, the Delta will not be pristine.
Deforestation, caused by forests cleared for agriculture, or logging for timber, is yet another problem that is resulting in increased runoff, and soil erosion. Von Brandis mentioned that erosion caused by deforestation can lead to mudslides that disrupt the rivers.
Water diversion and abstraction from rivers are also altering the natural flow and reducing the amount and time of the water to reach the Delta. The talk of proposed dams upstream have raised concerns among conservationists, who warn of irreversible damage to the ecosystem if it were to be dammed.
The human population in the Okavango Delta and the catchment areas is said to be growing rapidly, which increases the demand for water, land, and other resources. This puts immense pressure on the ecosystems, as more land is converted for agriculture, housing, and infrastructure. All that results in habitat loss that threatens the Delta’s biodiversity to function efficiently. Over-population also contributes to livestock population - cows and goats. More livestock leads to overgrazing and degradation of the river.
Von Brandis said that during the 2021 research survey along the Kavango River, they found high concentrations of nitrates, e-coli as well as plastic. These pollutants are said to be harming aquatic life and pose a direct threat to the health of local communities who rely on the river for drinking water and fishing.
Another growing problem facing the Okavango Delta is the unwelcome invasion of some foreign invasive species. Von Brandis said plants such as Salvinia Molesta (Mochibambo), which is wreaking havoc in the Delta, is a prime example of invasive species disrupting the Delta ecosystem. He also mentioned the Nile tilapia, a fish that is outcompeting native species for resources, saying that if left unchecked such invasive species could irreversibly change Okavango’s ecological balance.
Sand mining along the riverbanks is another human activity that could cause significant environmental damage and threaten the Okavango Delta. The removal of sand destabilises riverbanks, increases erosion, and alters water flow patterns.
According to von Brandis, mitigating these threats requires a dialogue between three countries along the system.
“Transboundary cooperation between Botswana, Angola, and Namibia is essential to address the root causes of these threats and ensure the sustainable management of the system’s resources,” said von Brandis.
He also recommended extensive research with some scenario modelling to predict what could happen in future.
He said the NGOWP’s conservation strategy of “Community-led systems of protection,” especially their work with local organisation like Fundacao Lisima, Kavango Wilderness Project and Nkashi Trust, from Angola, Namibia, and Botswana respectively, is another sustainable mitigating effort that could save the Okavango Delta.
