For years, biologists and ocean conservationists in Namibia have observed how climate change and human related interferences have shaken the country’s coastal ecosystem, including how offshore exploration activities, such as phosphate mining, could have detrimental effects on the ocean’s seabed. More recently however, there have been a number of strandings of marine species on Namibian shores, which marine biologists have taken as serious red flags and indications that the ocean is ‘not well’.
With three-quarters or 72 percent of the earth being covered in water, the global ocean contains the vastest, sensitive and most complex ecosystems on the planet. Ocean exploration is an ongoing process and numerous scientific studies show how the world’s oceans have changed overtime. Moreover, it has been observed that a lot of the damaging and irreversible effects are largely a result of human activity and the climate change phenomena.
Studies show that the global ocean has been warming up unabatedly since 2005. Global carbon emissions and human activities are not only affecting situations on land, they are also causing acidification, ocean warming and oxygen loss in the ocean. Ocean acidification, also described as “the other CO2 problem” in a 2009 scientific review, happens when there is a reduction in the pH of seawater, which in turn causes harmful effects on marine life, including plants and animals.
There are already signs and symptoms off the coast of Namibia which are linked to the heating of the ocean. In January, hundreds of jellyfish washed along a beach in the south coastal town of Lüderitz. A local report associated this phenomenon with overfishing. However, other studies indicate that there is also a connection between the abundance of jellyfish along coasts and ocean warming: these species flourish in warmer, deoxygenated water.
El Niño and La Niña
The National Oceanic and Atmospheric Administration revealed that extreme El Niño and La Niña events - two opposing climate events that disrupt normal conditions around the world - may become more frequent from about one every 20 years to one every 10 years by the end of the 21st century under aggressive greenhouse gas emissions.
El Niño and La Niña affect the world’s oceans and set off reactionary and extreme climate events around the world. Last year’s El Niño and La Niña cycle - which passed its peak between October and November - was one of the strongest since the previous 2011/12 cycle. According to the World Meteorological Centre, it impacted temperatures, precipitation and storm patterns around the world until April this year.
“The impacts of each La Niña on global climate are never exactly the same: they depend on the intensity of the event, the time of year when it develops and the interaction with other climate drivers – both naturally occurring and as a result of human influence.” - World Meteorological Centre
In extreme cases, episodes of El Niño and La Niña can take more than a year but usually last between nine to 12 months, and occur irregularly every two to seven years. Namibia’s cape fur seal mass die-off at Walvis Bay’s Pelican Point was a direct result of weather abnormalities caused by last year’s strong La Niña cycle. Namibian Ocean conservationist Naude Dreyer explains that seals were reliant on fish coming in at a certain time of the year but did not arrive on time because of La Niña.
In the past, this has happened on a smaller scale; in 1994, a similar and much stronger weather pattern occurred in which more than one third of all Namibia’s seals died. Asked about whether the seal population has been affected by this event, Dreyer says the seal population remains very strong. The localised die-off in 2020 only affected the central population of seals at Pelican Point, which “in a bigger scheme, is a small colony.”
According to Dreyer this colony consisted of 60 000 seals whereas the major colonies, , are around 200 000 to 300 000 seals. An estimated 10 000 seal pups perished during the localised die-off, which would have a small effect on the Pelican Point colony this year but would not affect Namibia’s seal population on a bigger scale, the conservationist states.
Impact on whales
The whale population in Namibia, which has been threatened by whaling activities, is endangered by the climate-change related factors which affect food supply for these species.
According to the Namibian Dolphin Project, there have been “clear indications” that the numbers of strandings and number of whales seen feeding annually off both, South African and Namibian coasts, seem linked to broad scale oceanographic events like El Niño and La Niña. This is negatively impacting the availability of food for whales, especially those passing through the coast of Namibia, and is leading to increased numbers of stranded animals along the country’s coast.
Marine mammals that are stranded, especially whales, are frequently sick or emancipated. Bridget James, a PhD student and researcher at Namibian Dolphin Project, informs that the waters off the Namibian coast act as a highway for humpback whales when they migrate between breeding grounds off Angola and feeding grounds in the sub-Antarctic. If animals have not succeeded in finding sufficient food to bulk up before embarking on their migration, James says, they may not have reserves to make the entire journey.
The researcher further explains that the bulk of stranded humpback whales off the Namibian coast are also juvenile animals (approximately 8 metres in length) that are undertaking their first solo migrations and may lack the experience to find sufficient food for the journey, resulting in their starvation and subsequent stranding. She says humpback whales are passing along the Namibian coast during their winter migration to their breeding grounds off Angola, while southern right whales are infrequently seen due to the previous decimation of their numbers due to whaling.
Since the moratorium on whaling in 1986 and the cessation of the commercial hunting of whales in southern African waters, the numbers of whales has been increasing steadily, as reported by JamesHowever, the current growth rate may be lower due to the effects of the recent La Niña. She says previous estimates suggest the humpback whale population was growing at a rate of 10,5 percent a year and southern rights at a rate of 7,5 percent per year.
After decades of whaling activities, southern right whales are now infrequently seen off the coast of Namibia. According to James these whales were the main target of whaling activities in Walvis Bay between 1785 and 1805. As their numbers began to decline due to whaling whalers then switched to hunting faster-moving humpback, fin, blue and sei whales between 1912 to 1914 and 1923 to 1930.
Although the whales in the southern hemisphere are steadily increasing, scientists observed that humpback populations in the northern hemisphere aregrowing at a much slower rate because of ocean warming.
Pollution and human interference
Namibia is a country that sees the most diverse parts of nature the Namib Desert is found along the east coast of the country followed by the South Atlantic Ocean off the coast. Although Namibia, among other sectors, benefits from tourism and the lucrative fishing industry, these are the same sectors that threaten marine life.
Currently, the biggest threat to Namibian marine mammals and turtles is marine pollution. Conservationists and marine biologists observed cleaner beaches during last year’s national Covid-19 lockdown which took effect in March last year but are still concerned about ocean pollution as things return to normal.
Marine species that prey on fish are also ingesting microplastics which have been consumed by the fish, including humpback whales.
“Seals at Namibia’s coast are being disentangled from marine debris such as packing straps, discarded fishing line and gillnets, while marine turtles such as leatherbacks are particularly susceptible to ingestion of plastic bags which mimic their jellyfish prey,” Bridget James, Namibian Dolphin Project
One way to reduce ghost fishing gear, James said, may be to incentivise the collection of such gear and properly dispose of nets and shifting away from the use of nets towards more targeted longline fisheries to reduce bycatch. With the increase of developments between the coast’s major towns, Swakopmund and Walvis Bay, marine biologists fear it may cause a spike in pollution on beaches.
Human activities such as beachfront construction and renourishment, seawall construction, nearshore dredging and oil platform construction, are among other harmful activities that interfere with marine life. One of the biggest challenges coastal dolphins face is habitat destruction due to coastal development; however the effect of such modifications is often subtle, the field officer states.
In turn, vulnerable sectors of the dolphin population such as moms with calves are moving away. Due to how subtle the shifting away happens, ongoing, year-round monitoring of the habitat use of the population is required as well as individual level data to see which animals are using which areas and if shifts in their habitat use have occurred.
Conservationists predict that the increase of coastal developments on unoccupied land and beaches will only increase pollution. Despite their concerns about phosphate mining, the Namibia Chamber of Environment describes its effects on the seafloor bed as “minute” and say that the area in which phosphate mining occurs off the coast of Namibia “has no particular importance to the fishing sector or to the marine ecosystem”. In spite of this, or rather precisely because of this it is imperative that scientists and ocean conservationists in Namibia continue to closely monitor the effects of these human activities of the coast of Namibia.