Ecosystem may save us

IN 2012, a report titled “Insights and opportunities offered by a rapid ecosystem service assessment in promoting a conservation agenda in an urban biodiversity hot spot” was produced for the City of Cape Town by PJ O’Farrell, PML Anderson, DC Le Maitre and PM Holmes.

They prefaced their report with a remark that proper ecosystem management, aimed at protecting biodiversity, has socio-economic value. Cape Town is a “recognised biodiversity hot spot” because of competing land uses.

Cape Town is a serious problem in respect of coastal zone protection and flood mitigation capabilities. Climate change will test the city fully.

In a short while the conservation of remnant vegetation will surface as a significant issue because “natural vegetation generally provides the highest level of soil retention”, which in turn prevents stormwater systems being filled with sand. When it rains heavily, this becomes a big headache.

For Cape Town there is an even more significant aspect to consider: there are “critical infiltration areas within the city (that) play an important role in absorbing large volumes of rain water”.

As our dependence on rain water grows, the need to recharge aquifers properly will assume significant importance. Cape Town was once characterised by “extensive coastal wetlands” but sadly that has changed.

As councillors we are already under the cosh because of our failure to anticipate the water crisis and have solutions in place. Public anger will grow if they learn the city commissioned reports and then let them collect dust. So what should we be doing with this report?

The report indicates “the highest groundwater yielding areas are the coarse sands of dunes in the north western areas and the southern areas”.

We should be protecting these with all we are worth. In their view, “the groundwater recharge potential for the city is strongly linked to the rainfall and also to the permeability of the rock formations and the associated soils”.

They identified areas of sandstone fynbos in the peninsula and in the Kogelberg and adjoining granite fynbos areas as having the best groundwater quality. The Atlantis Sand Fynbos in the north, similarly, has a high water quality. They also provide high yields and are important “for both current and future extraction”. They therefore need to be prized and protected.

“Much of the groundwater in the southern region area”, the researchers found, “has become polluted”. This is because high amounts of nitrogen and phosphorous are leaching into the soil. The poorest quality of groundwater, according to the study, is found below shaleassociated vegetation in the east. A similar situation prevails on the Cape Flats in the west where Sand Fynbos is found.

A complete ecosystem assessment needs to be made so the city can revise its policy and guarantee that recharge areas above the highest quality of water remain in pristine condition and are free of any developments. In areas where pollution exists, mitigation endeavours must be put in place. The ball is in the DA’s court.

See https://www. ecologyandsociety.org/vol17/iss3/ art27/