UNDERSTANDING ALIENS

One wine farm in Somerset West is on a mission to turn back the Cape ecological clock and unlock the potential for indigenous plants and animals to thrive.

THINGS I DIDN’T KNOW when scaling the heights of Vergelegen farm on the banks of the Lourensford river:  It was the last Cape Colony farm owned by a Dutch East india Company employee.  Willem Adriaan van der Stel’s extravagance on the estate is what got Adam Tas locked in the Castle of Good Hope’s “Black Hole”.  The farm is the unofficial genesis of Cape Dutch architecture.

But none of that matters right now. My only current concern is the contrast between the destruction caused by the 2017 #Capefires at Vergelegen versus the charred remains of Lourensford, its neighbour on the west bank of the Lourensford river. While the vegetation is recovering nicely on the slopes of Vergelegen, Lourensford is mostly scorched pine trees. The difference? Vergelegen has been clearing alien vegetation.

“Not only do alien trees consume 60 per cent more water than indigenous vegetation, they also burn more intensely,” explains Jacques van Rensburg, the estate’s environmental project manager. The estate started clearing alien vegetation in 2004, with 2 200 hectares originally earmarked. So far, around 2 000 hectares have been cleared, a practice said to have created 230 jobs. Whereas the project has its roots as a successful play for the Biodiversity and Wine Initiative (a World Wildlife Fund initiative to stimulate the adoption of biodiversity-friendly farming methods) honours, it is now fertile ground for various Cape ecological case studies.

“For the Cape in general, more than 70 per cent of the natural vegetation has been lost since the the 1900s because of agricultural and urban development. The 30 per cent that remains has now become heavily invaded. In wetter areas, it is predominantly acacia species (wattle, bluegum) and further up the mountains you get more pines. In 2004, we reviewed the farm after the large fire in 1997 which covered almost 1 700

hectares of property – the farm is 3 000 hectares – which was mostly in natural areas. Because a lot of the invasive species we have on the property come from Australia, they are also well fire-adapted,” says Van Rensburg

That fire adaption and intense burning means that the indigenous vegetation gets destroyed in the inferno and the seeds of the alien trees survive. Case in point is a pine tree. If the cone explodes because of the heat, it spreads the seeds into other natural areas and that plant out-competes the indigenous shrubs. “We found that annually the distribution of invasives increases by between 5 and 8 per cent, which means you lose indigenous plants by that percentage each year,” he continues. The other problem is that the intense heat causes soil problems because the heat penetrates a lot deeper, which further negatively impacts indigenous seed cover.

A large fire in 2009 ravaged around 2 000 hectares of the farm, engulfing much of the 1 700 hectares of land cleared up to that point. It also consumed some uncleared stands, but didn’t cause any significant agricultural damage. The fire did, however, spawn a regeneration of invasives. This forced Vergelegen to start a project devoted to reclaiming that land, alongside the clearing project. To give some perspective on the destructive power of invasives, Van Rensburg explains that the massive fires in January 2017 covered roughly the same area as the 2009 blaze, which raged for two months, #Capefires lasted a mere four days. Thankfully this year’s fires tore through a significant portion of the 200 or so remaining hectares earmarked for clearance, of which six have been cleared since the teams got back to work.

Fynbos fires generally occur once a decade. In fact, the Cape Nature rule of thumb is that a blaze is due after about three protea-flowering seasons (proteas flower after five years of growth). If the veld doesn’t burn it can become sterile, but too-frequent fires aren’t good either. A major fire within eight years isn’t terrible, but the farm now faces erosion problems such as roads washing away and dams that are silted up. The fires did assist the initiative by incinerating a lot of the excess biomass situated in inaccessible areas. Vergelegen had actually planned to do the Cape’s first aerial ignition controlled burn, but Mother Nature (or was it Human Nature?) stepped in with the help of a few suspected arsonists.

Another unexpected side-effect of the clearing project has been the rejuvenation of some streams that usually ran dry in summer that now run all year round. the farm is lucky enough to be in a catchment area. Two of the three dams on the property are at 100 per cent, with the third at 60 per cent. The farm is entirely self-sufficient for irrigation purposes. Unfortunately, the water isn’t potable.

This mass clearance of alien vegetation has also had other effects. Because the fires are less destructive, there is a greater opportunity for the associated fauna to settle. A healthy bontebok herd roams freely across the estate and 145 recorded bird species fly overhead. The antelope are also ranging further up the mountain slopes than expected, which puts them at risk of attack from the Cape leopard population in the Cape Leopard Trust Boland Project study area that extends into the farm. Of the more than 280 fynbos species documented on the farm, 22 of them are on International Union for the Conservation of Nature (IUCN) Red List, a peer-reviewed account of the planet’s most threatened plant and animal species.

Outside of the alien vegetation clearing, Vergelegen also monitors the estate’s Cape leopard population with motionsensitive night vision cameras. The farm is experimenting with strategically placed catnip to attract the cats.

Many species of Boland Granite fynbos, thought to be extinct, are flourishing on the farm and recovering well after the fires. Van Rensburg and his team are going to crossreference findings with records from the estate’s historic library.