How plantations work towards ecological balance

Mail & Guardian

a day ago

Corridors of natural vegetation are essential in plantations if biodiversity is to survive. Photo: File
Nature conservation is about conserving not only the huge number of species but also the myriad interactions between all the players on the same ecological stage. Moreover, all these species need a complex assortment of microhabitats to find food, disperse, mate, reproduce and develop into adults.
But, with so many species and even more interactions, we must find ways to conserve the overall fabric of life. This is something that we should also reflect on as we celebrate World Nature Conservation Day on 28 July.
Finding the solutions is vital for South Africa because it has a rich diversity of plants, fungi and animals — and an untold number of micro-organisms. Across landscapes, groups of species and their interactions change from place to place. Furthermore, the organisms in this mosaic must ebb and flow across the landscape in search of optimal conditions for feeding, growing, reproducing and surviving. This flux of organisms also helps maintain healthy levels of genetic diversity in their population over time.
Another challenge is that many of the species live in specific habitats. Damage to the habitat can lead to loss of a species — possibly even causing local extinction — and begin to unravel the thread of life.
A starting point is to conserve nature and embrace the 'Nature knows best' principle. While nature reserves play a crucially important role in conserving biodiversity, the greatest challenge lies at the interface of human activity and the conservation of nature. This means we must find workable solutions that benefit both people and nature where they live side by side.
A way is to embrace the 'precautionary principle', which involves conserving as much land and water as possible to avoid imperiling all species and their interactions.
Timber production is important for South Africa because it has few natural wood resources, with plantations covering huge swaths of land. But how do we integrate nature conservation with timber production? After extensive discussions with timber company Mondi, we at Stellenbosch University developed a workable solution — acceptable to both timber producers and conservationists — by working with nature and not against it.
The solution involves setting aside land between plantation compartments — land amounting to about half a million hectares nationally. These land areas take the form of networks of large conservation corridors of natural habitat, composed of mostly natural grassland, but also forests, wetlands and small rivers. These networks make up about one-third of the plantations, on average, and are well established in KwaZulu-Natal.
It has been essential to demonstrate that the corridors are indeed functioning naturally. We have done this by comparing biodiversity levels in the conservation corridors with those in nature reserves nearby.
As not all biodiversity can be sampled, we use mostly plants and insects as sentinels. The reason for this is that they are numerous, rich in species, show a wide range of lifestyles and are sensitive to habitat change.
A bonus is that they also live in and on the soil, as well as being associated with plant communities. Many are also associated with freshwater — whether streams, rivers or wetlands. As they interact widely with many other species, they provide a comprehensive ecological picture.
Importantly, the corridors must be as wide as possible to avoid any adverse effects from the adjacent plantation trees, mostly alien pines and eucalypts. This great width, which ideally should be more than 120m, means that all the natural interactions and processes can take place as they would naturally. But this does not mean that narrow corridors are without value, as many natural interactions can still take place in them and they promote the movement of insects and other organisms across the landscape.
It is essential that the corridors are well connected to each other in a network, including from one plantation to the next. Doing this leads to congruence among natural habitats over hundreds of kilometers, crisscrossing all types of terrain, elevations and ecosystem types. Crucially, it is the enormous amount of conserved landscape variation that enables organisms to find their most suitable habitat. This connectivity also gives the landscapes ecological resilience to withstand a changing climate and extreme weather events such as heavy rainfall or drought.
All the while the natural water systems and soils in the corridors are maintained as intact as possible. This is done by not planting timber trees close to streams, rivers and wetlands. In turn, moist soil acts as a sponge for water and supports lush vegetation, which is kept free of plantation trees to help maintain the movement of natural ground water.
Fire must also be considered, as it is a natural phenomenon in the area— preventing the grassland from developing into a bushy landscape and playing a vital role in the health of many plants.
The edges between natural forest and grassland are also protected in the corridors, because these transition areas support many rare and important species. Game animals are also left to roam in this mosaic of vegetation as they help maintain grassland health.
Some difficulties have arisen in these networks of conservation corridors. Invasive alien plants are an ongoing problem. While the woody aliens are controlled relatively easily, it is the American bramble that has been most troublesome. But recent research, using satellite technology and machine learning, has identified the weed's invasion pathways, enabling swift and effective bramble removal.
Local people are involved in the establishment of corridors, and they use the land as pastures for moderate levels of cattle and goat grazing. Poaching of large mammals is strictly controlled, resulting in healthy populations of elephants, rhinos, giraffes, zebras, wildebeest and many other large animals. This is important for insects as these large animals support a rich variety of dung beetles.
In turn, firebreaks help stop wildfires from entering the plantation compartments. Also, timber tree harvesting is carried out sensitively to reduce disturbance to the soil.
Plantations benefit from implementation of the corridors in that the soil and water systems, along with their biodiversity, are maintained in an ongoing healthy state. Mondi has embraced sustainable forestry. In doing so, the company attains Forest Stewardship Certification and exports products to Europe and elsewhere.
Michael J Samways is Emeritus Distinguished Professor in the Department of Conservation Ecology & Entomology at Stellenbosch University
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