The Namibian government is considering whether or not to open up its offshore phosphate deposits for dredge mining. But before it does so, it wants to make a careful and considered decision based on independent analysis of the likely impacts on the environment, and how other competing industries might be affected.
The Namibian government, with the help of an international body, the Convention of Biological Diversity (CBD), hosted a workshop in Windhoek in October, bringing together experts in various fields, following an environmental impact assessment (EIA) on offshore phosphate mining.
This is according to resource economist and associate professor Prof Tony Leiman, with the Environmental Policy Research Unit (EPRU) at the University of Cape Town, who was one of those invited to present at the workshop.
Namibia has three primary sectors which dominate its economy: agriculture, mining and fisheries.
‘The mining cluster has an interest in this project going ahead,’ explains Leiman. ‘Fisheries and conservationists have expressed concerns over its potential impacts on the small plants and animals of the seabed, and the commercial fish species that depend on them.’
In order to balance these competing interests, Leiman says that the Namibian government hoped to bring in independent experts who could give an impartial and objective view.
Although researchers have studied the impact of diamond dredging in the waters off southern Namibia, Leiman says less is known about the specific impact of phosphate mining in waters further north.
Phosphate mining involves dredging the seabed by breaking up a shallow layer of rock phosphate, which is vacuumed up onto a ship. The water, and residual sand or ‘fines’ in it, are returned to the sea. This returning waste forms a plume that slowly settles on the seabed.
Ecologists at the workshop emphasised that the plume’s impact will vary, depending on the different conditions of each site, such as current strength, water depth and oxygen levels. For instance, life on well-oxygenated seabeds might recover quickly, while lower oxygen environments, which are common in the area, might take a lot longer to recover.
‘Although the environmental impacts of diamond dredging and marine sand mining have both been studied extensively, there has been little opportunity to study the effects of large-scale offshore phosphate mining directly,’ explains Leiman. ‘The protocols, appropriate legal framework, profit margins and mitigation options are less clearly understood.’
The initial request has been for permission to dredge four square kilometre sections of seabed yearly. The process normally involves removing a relatively shallow ‘cut’ of about 0.4m of shell and accumulated detritus which has settled over the rock. The phosphate which lies beneath that would then be extracted. Unlike diamond dredging, which sucks out gravels down to the underlying rock, phosphate dredging would leave a soft seabed of clay behind.
‘There are two important questions. Does the shape of the stripped area affect its recovery? And if recovery is slow, could such mining affect the hake fishery significantly? The point is important if one considers the impacts over time.’
If square sections are slower to recover than long narrow strips, which are easily repopulated, then the kind of technique that is adopted can affect the environmental costs of the mining. Taken over a century, 4km2 dredged each year would translate into an area of 20 square kilometres, Leiman explains.
Hake is Namibia’s most economically valuable fishery. While most fishing happens in deeper waters, younger hake are found in shallower waters and, as they grow, move through the areas in which dredging is likely to take place. Their primary prey are bearded gobies, and uncertainty remains about the possible impacts of mining on this species.
The market for rock phosphate is another reason for some uncertainty about whether or not mining these reserves will be economically viable.
Phosphate is normally a ‘low value’ resource. The rush on applications to mine Namibia’s reserves was spurred by concerns that global supplies of this rock-born non-renewable resource were dwindling and demand was rising. Instability in North Africa, with the Arab Spring, further heightened concerns about the mineral coming from Morocco, one of the primary global suppliers.
However, Leiman says that earlier predictions about the looming threat of ‘peak phosphorus’ are being revised, and that supplies may not run short as soon as predicted. Recycling of phosphates is another option in future, where the mineral can be recovered from sewage.