Living on the Edge

Ecologically speaking, on the edge of a vlei, on the edge of a forest, on the edge of a water body means that you are also on the edge of some other habitat. We are not isolated in this world and every type of habitat adjoins another type. This interface between  habitats  is  usually  called  an 'Ecotone'. These ecotones are normally the most inhabited and therefore the most important parts of the environment.

For instance, sable rest in the shade of a woodland and then venture out into a vlei to feed. Crabs take refuge and feed in water and then venture out onto the shore to feed on other foods and to burrow. Birds sit in trees at the forest edge and hunt out into the grassland. The littoral zone of the sea shore is a well known and much publicised example.

While animals find ecotones the most attractive areas to live in, human beings, wishfully at one with nature, have the same attraction. One only needs to survey the number of coastal cities and towns on each continent. The shorelines of large lakes, river banks, forest edges, areas adjacent to mountains are all sought after dwelling sites. With insensitive humanity there is obviously going to be a clash with the natural world. The effect of effluent and emissions has even further impact.

On the local scene and in other rural areas the effect of humans can be just a damaging if proper ecological planning is not taken into consideration during 'development' schemes.

The edges of vleis make a firm, cleared and attractive site for roads. Rivers offer natural boundary lines between properties. Open grasslands, which are quite often flight paths, offer uncluttered routes for power lines. Generally the ecotones are an easy option for development. The hazard of power lines to flying birds is well docu- mented. Roads along grassland or vlei edges pose a great disturbance and sometimes a physical hazard to animals using the ecotone.

With our extensive shoreline, vehicle travel along the marine littoral zone by careless humans is well known. The same applies to roads and other activities on the shores of 'dams' and lakes. One positive factor of cleared areas along ecotones is that they provide firebreaks between habitats with different burning regimes.

The point intended is that landowners and developers should be aware of the poten- tial damage and disturbance that can be caused by expedient use of ecotones. Rather zig-zag roads in and out of forest edges. Instead of a ring road round a dam have in/out roads down to view points. Place water points where the hoof pressure will not cause erosion to valuable grazing areas.

Quite often the different habitats will be characterised by differing soils types and these soil contacts often coincide with the ecotones. Where the soil contacts result in 'sodic' conditions extreme damage can be caused by aligning roads along the attractive, sometimes bare and very 'brittle' areas.

Before any action takes place survey the area. Note what lives there and put yourself in the place of the natural inhabitants. Make the utmost effort to disrupt other life cycles as little as possible. Because humans are part of the world there will always be some effect by anything we cause.

Winrows on a graded road may not seem much to us but they are insurmountable mountains to a tortoise or to some insects. Trapped on an open road they 'fry' to death unable to escape the heat of the sun. Animals may miss their vital daily drink by vehicle distur bance cutting off their access to water. Low 'hot wires' on electric fences are death traps to tortoises, pangolins and young carnivores needing to cross human boundaries. There are many examples.


While on the subject of habitat abuse and while we are experiencing the effects of a drycycle in our rain pattern, animal pres sure on fenced and confined areas needs mentioning.

The soil is the foundation for plant life. The plants are the only food source for ani mals. If the plants are placed under too much pressure they will adjust by diminish ing in succession to lower quality pioneer plants. With less palatability and lower pro duction the carrying capacity for animals is further reduced and lack of cover causes permanent soil damage through erosion.

Many nonresident 'game farm owners' who wish to show off 'their game' during infrequent visits, seem unaware of the dam age they are causing. High game concen trations are not a natural feature of the lowveld. Aggregations occur at certain times of the year, for various reasons but should not be simulated as a permanent spectacle to be viewed when convenient.

By over stocking these fenced areas, from which animals are unable to migrate, they are not only causing siltation of our rivers through erosion but are per ma nently destroying the country's natural assets.

The resident game managers, who  are employed because of their expertise and  landman agement abilities are put in a most invidious position by the committee decisions of some highhanded, greedy individuals. Feeding schemes, apart from certain cases for some rare species, are a complete waste of money that could be put to better use in the conservation of the areas. In most cases feeding makes the situation worse.

The legislation exists and will soon be enforced to prevent land abuse. In the country's present political climate, certain individuals could not be adding bet ter fuel to the cause of land claims. The grazing of cattle under intelligent man agers would probably cause a lot less land damage than that presently being caused by confined and over stocked game areas.

All damage is caused by greed for numbers and confinement, which is far removed from conservation. These days it is a political knife edge. The only future for these game areas of low carrying capacity is the removal of fences and unselfish attitudes that will permit traversing rights to game concen trations. The selfish attitude of confining unsustainable stock on marginal land has already caused irreversible land damage.

Owners would be wise to leave land management decisions to the managers they employ and let them get on with the job with the committee support they deserve. The alternate is a disaster, with the birds coming home to roost with a vengeance. 

Dave Rushworth

Kruger National Park - South African Safari