- Biodiversity loss
Here is an enlightening presentation on the importance of grasslands made at the TIMBERWATCH SYMPOSIUM:
‘Industrial Timber Plantations in South Africa’
Pietermaritzburg, 10 JUNE 2000
The value of grasslands
Prof. Braam van Wyk
HGWJ Schweickerdt Herbarium, University of Pretoria, Pretoria
Policy-makers need basic information in order to make rational decisions on their various crucial and pressing issues, which is where botanists and in particular, plant systematisists, can make an important contribution.
There are very few parts in SA where there are still unspoiled grasslands as far as the eye can see; unfortunately that is a thing of the past. But why be concerned about these grasslands? Are there not other more serious issues, namely, the removal of forests by man over many years, perhaps through the use of slash and burn, agriculture, or the unwise and excessive use of fire? By establishing plantations of timber trees in grassland areas, are we not reclaiming what used to be forest? Sadly, that was the view of many of the early ecologists who worked in southern Africa and who were of northern hemisphere origin, where grassland is seen as a sign of degradation and by practicing afforestation you are putting back a tree-dominated system. That interpretation has been shown to be seriously flawed, although the same argument is still surfacing today in some of the forestry publicity. Some of our greatest ecologists like John Acocks and even the late Frank White were supporters of the view that grasslands are mainly anthropogenic, i.e. man-made.
The conservation status of grasslands is low, relative to forests. This is strange, since in a way all the carbon in our bodies, derived from carbon dioxide in the air, must have been part of a plant once and the bulk of that carbon comes from the grains that are the staple food of mankind. So the grasses are actually keeping us alive. Quite literally: all flesh is grass. Grasslands may not supply grain, but we still harvest this resource in the form of animals, sheep and cattle for example. Animals transform the plant material into products that can be consumed by humans, such as meat and milk. So it is food that we’re looking at, it is ourselves that we’re looking at. And when we die we end up as carbon, if we are assimilated into the air. That brings us to the basic concern of us as biologists, that there is a basic lack of respect for life. All forms of life are inter-linked, and we are just temporarily sharing that flow of carbon that is fixed here on earth.
I would like to point out a few interesting facts about our grasslands which will help to illustrate the lack of concern about the biological component of our environment. I know there is the concern about the physical, the social, and the economic implications, but until recently the biodiversity/biological aspect has played virtually no role in the issuing of permits and in plantation industry decisions.
Plants possess a property that most animals do not have, as a completely different form of life. Plants are stationary organisms, unlike the animals except for corals which imitate plants. Plants stay in one place, even a couple of thousand years in the case of some species. This property means that they create habitat which can then be occupied by the rest of the animal kingdom in addition to certain plants. This habitat-creating aspect of plants is called “vegetation”. There is a lot of misunderstanding, thinking that vegetation is just interchangeable. When we talk of vegetation we talk about the general effect produced by the combined growth form of all the plants in an area regardless of their species composition. If it is a system dominated by trees, then it can be called “a forest”. That is why a plantation—a monoculture of trees— is sometimes also called a forest, because structurally it is dominated by trees. If plants with a grass growth form dominate it, it is called “grassland”, and if there is a mixture of trees and grass it is known as “bushveld” or “savanna”. Areas relatively uniformly covered by any of these broad vegetation types usually represent major biotic zones and are often called biomes. What is the cause of these biomes? They are mainly determined by climate. Where the climate seems to match that of other parts of the world, a similar vegetation type or biome is found.
Are there other parts of the world which have similar sets of conditions conducive to the formation of grasslands? There are, but not many. For example, in North America there are the prairies, in South America the pampas, in Hungary the pusztas, in Asia the steppes, and in SA our own high altitude and coastal grasslands.
Californian grasslands (and ones in Europe, the UK and in many other parts of the world) are in fact man-made, caused by the destruction of the natural climax vegetation, i.e. they are secondary grasslands, a sign of environmental degradation. Ecologists initially interpreted our southern African grasslands in this way too. We now know our grasslands are primary grasslands, they are the climax vegetation type for those regions where they occur. These primary grasslands show remarkable and interesting characteristics.
What is the cause of the grassland biome in southern Africa? This is not known for sure, except that temperature, rainfall and especially fire is crucial in maintaining our grasslands. To that we can add grazing by herbivores that this vegetation type has evolved with over millions of years. But the fire is crucial for its survival - natural fires. The grass plant is adapted to grazing, as if it was made by nature to be grazed to the ground. It is difficult to eradicate it through grazing, although it can be impoverished by it. Grasses behave differently to other plants. For instance they grow from the bottom and not only from the growing tips of stems. If a grassland is grazed its productivity is increased, it is stimulated to grow. The saliva of grazers even contains growth-promoting compounds that stimulate the growth of the grass plant.
In a grassland individual grass plants dominate in numbers because grasses have the strategy of being wind-pollinated. One of the syndromes of being wind-pollinated is to grow en masse, or else it is a very wasted effort on the part of the plant to throw its pollen to the wind. Gregariousness is a feature of most wind-pollinated plants. Plant species occurring in dense stands in nature, almost as monocultures, are almost invariably wind-pollinated, for example mopane (Colophospermum mopane), Lebombo ironwood and tamboti (Spirostachys africana).
The habitat aspect is especially important to grassland birds. They are not so concerned about the particular plant species in an area, but rather whether it is an open or closed habitat. To many of the bird species it does not matter if it is an alien grass-dominated habitat, for example a sugar cane, wheat or maize field.
Southern Africa is an extraordinary area floristically: it has more than 24,000 species which is almost 10% of the world’s flowering plants concentrated on about 2% of the earth’s land surface. That makes us vulnerable to destructive forms of activity. No other country in Africa, even large ones in the tropics like Zaire, can match this biodiversity. This is an incredible natural resource, a genetic material resource that we must treasure and be made aware of. Why would large international pharmaceutical companies try their level best to do bioprospecting in SA for medicinal plants? There are very few other places in the world they can go to. Being so rich in species creates problems which we must be aware of, and devise our own solutions to, and not just take over the solutions found in other, more floristically impoverished parts of the world.
In a sense, “grassland” is a misnomer. Although grass plants may dominate when you look at the veld, we know that the majority of species in a native grassland are non-grassy herbs: they are the so-called wild flowers and in terms of species they outnumber grasses by about 3:2. Up to now our ecological research on the dynamics of grasslands has focused mainly on grasses because they are the ones that are important for domestic stock and hence in pasture science. Our knowledge of grasslands is mainly based on the behaviour of grasses whereas the non-grassy herbs have been neglected. Yet the vast majority of the rare plants in the summer rainfall areas of SA are non-grassy herbs in the grasslands – not the forests.
The behaviour of the non-grassy herbs in native grasslands is rather different to the behaviour of such plants in other grassland regions of the world, e.g. to the long-grass prairies which have been 95% destroyed. When a grassland turns from dull and brown in winter to green and lush in summer, there is hardly any seed regeneration. That must be remembered. The system is a stable one of resprouters—the underground structures (e.g. rootstocks, bulbs, tubers) in many species being decades if not hundreds of years old. Although seeds are produced, those of particularly the non-grassy herbs are hardly taking root, that is why it is so difficult to re-establish a grassland from seed. Plants do not move around like animals; when you establish a plantation or any other form of destructive development in one area they can’t flee like antelope or most larger animals. Our non-grassy herbs, these rare plants, are often confined to small localised pockets in grassland and may stay in those positions for decades if not hundreds of years. Some of these species seem to have lost the ability to re-generate themselves from seed, perhaps because in the past there was no dramatic factor causing the same degree of destruction as the plough in this part of the world. It’s not like the dunes in Richards Bay, it’s not like the Kalahari where there is nothing but rain and sun and wind, or the Namaqualand where there are still the annuals that can fill that pioneering position. Many of the annuals we have in our high-altitude grasslands are naturalised weeds, species that we have brought in from other parts of the world. Thank goodness for the weeds that have filled that niche, one that seems to be lacking in the natural system, which means that when you plough the field it has difficulty in regenerating itself.
Overgrazing of grassland can be coped with quite well because it emulates the antelopes that once roamed the veld. Underground structures are a major feature of the non-grassy herbs in our grasslands, and in some species, like Boophane disticha, the bulb is estimated to exist for as much as 500 years. After the dry season (winter) we get the pre-rain flowers, a very interesting group of plants. In these underground structures they store water and nutrients that build up during the summer because these plants “want” to flower in spring before the grasses grow out and before mass flowering of the grasses obscure the advertisement of their flowers to the pollinators. The pre-rain species flower in August and September when much of the grassland is still black and dry, when most people think there is nothing to see. But there is a lot more to see than in January when the grasses have dominated the veld. In just two or three weeks some of these pre-rain flowers have produced their fruit and seeds which is amazing because they apparently “want” the seeds to be there when the first spring rains fall, so that they can establish themselves by the following winter. Because they are so old, and because they have been in the same position for decades, most of the non-grassy herbs seem to have built up an arsenal of chemicals that protect them against herbivores and insects. This is why a very large part of our medicinal plants are found in grasslands. The active compounds they contain are the poisons produced by these plants to give them that survival mechanism to cope for so many years in the same position.
Floristically southern African grasslands are very rich. At the 1000 m2 scale Renosterveld in the Cape has an average of 86 species, grassland has 82, Succulent Karoo has 74, and Fynbos a mere 68 species. As you can see in the new Botanical Society poster, grasslands support a whole range of fauna. There are about 170 mammals dependent on that grassland—eight are confined to the grassland biome alone. Most of the large herds of native antelopes have disappeared; once there were millions of them.
One can still see the monuments left by these large herds of grazers in the huge polished rubbing stones, before man eradicated them. Cattle, sheep, goats have tied in with the historical way of utilising these grasslands. There are many birds, mainly brownish, grassland-adapted birds - possibly about 50 subspecies of birds; it is one of the bird-endemic regions of Africa. At least 50 species of butterfly are more or less confined to grassland. A lot of reptiles, and other creatures are not capable of living anywhere else.
But what are the threats? Firstly, plantations that change the grassland habitat to a tree-dominated habitat. Once plantations have been established, the local plants can no longer live there, the animals can no longer live there, but because of the resilience of the veld some survive for a time. In a way, an established plantation is no different from an opencast mine: you destroy the habitat. An open cast mine of 200 km2 which until recently was the average area of new plantation established per annum, can you imagine the outcry? After you have removed the ore from a mine you can put back the soil and attempt to revegetate it to a grassland state. Reclamation ecologists can restore at least the structural component of the grassland habitat.
The scale of destruction by 'commercial afforestation' is what is so frightening. People say what about the sugar cane farmers and the maize farmers and the banana farmers. Look at the northeastern Cape, for example in the Elliot-Ugie-Maclear Districts. A few years ago there were about 50 000 hectares grassland sacrificed in one go for the establishment of plantations. This area lies along the Drakensberg Escarpment, which is the catchment of many of those rivers which feed the degraded Transkei.
If you looked at the earth it is a ‘hotspot’ in the universe, it is the only known part which has life, everything is endemic—so you could say no ‘development’ at all! But you must be realistic. Let’s look at floristic regions in southern Africa where the flora is fairly uniform. In a large floristic area destructive forms of development would not be so bad. In the Cape Floristic Kingdom, being the smallest of the world’s six floristic Kingdoms, it becomes a no-go area in terms of the size of all the other kingdoms so it assumes a special importance because of its size. Following the Rio Convention in 1992, there was an effort by the IUCN and WWF to have a more practical approach: let’s identify areas of highly concentrated plant diversity, especially ones with high levels of plant endemism, to assist governments to plan. They compiled a three-volume work entitled “Centres of Plant Diversity”. The first volume deals with Africa. Worldwide, 250 sites have been identified as areas of particular significance for the conservation of the world’s plants. Sites identified in southern Africa include the Cape Floristic Kingdom, the Maputaland-Pondoland Region, and the Succulent Karoo Region, the Pondoland Centre, the Drakensberg Alpine Centre, the Maputaland Centre, the Barberton Centre and the Wolkberg Centre. The Wolkberg Centre is the region with some of the most extensive man-made “forests” in the world – that is how the government and others often promote it. It is, however, one of the regions where the natural grassland has been extensively destroyed by commercial afforestation. In this region you have a mosaic of forest and grassland, and in the past the forests were conserved—or attempts were made—but the grasslands were considered of little significance and used for plantations. In the Wolkberg Centre, a fairly narrow area along the escarpment, there are about 120 species growing only there out of a total of about 2,000. Of those 120 endemics, perhaps five you would find in the forest; about 115 would be in the grasslands, and this preponderance of endemics in grassland applies to the whole of the summer rainfall region of SA.
If we look at the Centres of Endemism on a relatively old map and we look at the activity of the timber industry the areas planted up and potentially planted up, it may be one per cent of SA—but in floristic terms it is probably 90% of floristically some of the richest areas in our region. Furthermore, these are also the areas of the highest rainfall where we have our water factories; afforestation has been followed by a dramatic decrease in water flow. I am very hesitant to pay any attention to models although they are useful, but I have included actual stream-flow measurements that were made and that you rarely see in print—I think it is kept top secret by parties who do not want these figures to be known. The following statistics come from the Klaserie River below Mariepskop (Limpopo Province), where the only significant activity in the catchment has been an increase in afforestation (tree plantations): from 1935 to 1964, although the average rainfall has increased, there was a dramatic drop in the mean annual run-off from 143 million cubic metres to 16.5 million cubic metres (from Bothalia 10,3: 461–500, 1971).
Consider for a moment the conservation status of the Grassland Biome in southern Africa. Compared with the six other biomes in the region, it is by far the most threatened (% destroyed; % conserved in brackets): Grassland (60; 2.4), Forest (44, 24), Thicket (44; 6.4), Bushveld (43; 20), Fynbos (33; 6), Succulent Karoo (21; 2.1) and Nama-Karoo (<20; 0.47). Owing to regional variation in climate, geology and soil type, the Grassland Biome is not floristically homogeneous, but comprises a large number of different grassland types, also referred to as veld or vegetation types. The conservation status of a few of these grassland types clearly illustrate that some of them are more threatened than others (% destroyed; % conserved in brackets): Short Mist belt (90; 2.37), Moist Clay Highveld (80; 0), Moist Cool Highveld (72; 0.29), Moist Cold Highveld (70; 0.63), Dry Clay Highveld (67; 0), Rocky Highveld (65; 1.38), Dry Sandy Highveld (65; 0.28), Wet Cold Highveld (60; 6.72), Moist Upland (60; 2.52), Moist Sandy Highveld (55, 0.67), NE Mountain (45; 7.42), SE Mountain (32; 0.33), Afro Mountain (32; 0) and Alti Mountain (32; 12.53). Grassland is not only one of the most poorly conserved, but in many regions there is little potential for conservation of relatively large, intact areas in the future because of its radically altered state. In fact, it is doubtful whether certain representative veld types within the biome can ever be adequately conserved today, simply because there are no reasonably large areas remaining.
The Grassland Biome is the mainstay of dairy, beef and wool production in South Africa, and it contains most of our major river catchments. Grasslands occur on some of the best agricultural soils and are the cornerstone of the maize crop, hence most grassland types have been radically altered by agronomy. Furthermore, over the last number of years species-rich grasslands in our high-rainfall regions have been destroyed at an average rate of well over 200 km2 per annum by commercial afforestation alone. Urbanization is a major additional influence on the loss of natural areas—the Witwatersrand is centred in this biome. Transformation of grassland by ploughing and afforestation is considered irreversible. Although such areas can be re-vegetated to a state at least structurally resembling a grassland, the original floristic diversity apparently never recovers. The present Grassland Biome is the culmination of a succession of events over millions of years. The shifting of vegetation belts and biomes in historical times has seen the present Grassland Biome area periodically invaded by Nama-Karoo, Bushveld and wetter, dryer, warmer or colder grassland types. Man can never replicate these historical events, perhaps one of the reasons why it has proved essentially impossible to restore the full floristic complement once a piece of grassland has been destroyed.
The destruction of southern African grasslands is following the same trend which has almost wiped out other primary grassland areas in the world, notably the prairies in North America. We can learn a lot from their mistakes. Today large amounts of money are spent to save some of the few remaining natural prairie remnants. Also, considerable effort is being made to try and restore some of the original prairie ecosystem. We in southern Africa are heading the same way unless we come to our senses and realise what precious natural heritage we are destroying. Fortunately, in many areas we are still in a position to halt this neglect of our Grassland Biome, but time is running out fast.