South Africa has an amazing diversity of plants and animals. Many people know and cherish the most visible and charismatic wildlife, such as rhinos, elephants, lions and giraffes. A growing number of people are enjoying South Africa’s beautiful birds, and people are starting to appreciate the reptiles, frogs, and even some of the insects such as butterflies and dragonflies. Few people, however, are quite aware of what might be South Africa’s greatest living treasure; its plant diversity. South Africa boasts about 25,000 described species of flowering plants, and the Cape Floristic Region, supporting about 9,000 species, is considered one of the world’s six floral kingdoms. South Africa is also the country with the greatest diversity of succulents in the world! It truly is a treasure that warrants effort to protect.
South Africa’s botanical richness is definitely a national treasure, and the diversity of plants are vital to the diversity of animals – all animals depend directly or indirectly on plants. Plants provide food, medicine (even animals use plants for their medicinal values), shelter and building materials to so many other living things – humans included. Species that go extinct are irreplaceable. Every species that vanishes will have knock-on effects on other species, to their detriment, and also to the detriment of the habitat in which it occurred.
The conservation of plants is in many ways different from the conservation of mammals, birds or other animals. The big difference between plants and (most) animals, is that plants cannot move as individuals. On the up side, this makes them easier to work with. It is not necessary to find a way to capture or restrain a plant; you can just walk up to it (if it is in an accessible place). You can take photos, you can take a small piece as a sample or a specimen. You can collect seeds if there are any. There are challenges too, however, if you are in an area where a plant species is known to grow, finding it may be no easy task. Many plants occur very sparsely, meaning you have to hike for many hours before you’ll find even one, even in its prime range. It can be very hard to spot small plants amidst dense grass or scrub. Some plants are ‘invisible’ for much of the year, with their main parts subterranean (underground), sending out shoots only during the growing season. Some plants can only be positively identified when in flower, and their flowering periods may be brief; it is easy to miss them unless you go out into their habitat to search for them pretty much every single day. And some plants grow in difficult-to-access places: on cliffs or steep mountain slopes, in impenetrable, thorny thickets, like some epiphytes high up in the forest canopy.
One of the challenges with some plant species is that they have very small distribution ranges – in some cases, only on a single hill, or a small patch of ground with unique geological and environmental features. It is not always possible to figure out which particular ‘spot’ might host such a uniquely restricted plant species; therefore, seeing as there are many places in South Africa that haven’t been properly explored by botanists, there might be many such ‘range-restricted’ plants still awaiting discovery. Many plants might have already been driven to extinction because the spots where they grew, have been turned into towns, farms, plantations, mines, or submerged by the building of dams.
Some plants are sensitive to disturbance. Overgrazing of an area might lead to a decline in grass cover and an increase in dense growth of shrubs, trees, and weedy herbs. Bush encroachment can also happen when regular fires are excluded from an area. Bush encroachment leads to changes in ecological attributes, such as the amount of sunlight reaching the ground level. I have observed this in colonies of highly habitat-specific plants, such as a species of Euphorbia and a population of Lithops: what was initially open grassland, with lots of ‘room’ for these light-loving plants to grow, gets turned into bushland and the plants are ‘shaded out’ and disappear.
Human activities have caused major changes to the factors that determine the nature of the vegetation across most of South Africa. Migratory wild mammals have been replaced with fenced-in domestic livestock. Fire regimens are determined largely by human whims, in some places being too frequent relative to the needs of the local flora, and in other places the fire cycle has been suppressed.
The introduction of invasive alien plant species is also a contentious issue. Some examples of alien invasives include: Hakea and Australian Acacia-species in the fynbos biome, Opuntia prickly-pear cacti in the grassland, savanna and succulent thicket biomes, Lantana camara along rivers, the Kariba weed Salvinia molesta on large bodies of water, and Solanum mauritianum, Bugweed, in forest regions. These plants, once introduced to a region, propagate themselves and easily spread without any further help from humans. Because they come from different ecosystems in distant places, they typically don’t have any natural predators here. They can reproduce and multiply at a massive rate. They invade natural areas in large numbers, displacing the native plants that used to grow there. These invaders can be very difficult to eradicate; some can be countered by the introduction of their natural pests (bio-control), but others are more resistant and need labor-intensive physical removal methods.
Plants are able to ‘move’ by means of seed dispersal. They can distribute their seeds over small or large distances, depending on the durability of the seeds and the way they are adapted to dispersal. Under normal conditions, environments have always been changing, cycling from forest to grassland and sometimes even to desert and then back again. Plants could cope with this, moving to moister places if their own became too dry, to warmer regions if their own became too cold, and vice versa. The difference is that this was a slow process. Most natural changes in climate and factors influencing a particular habitat take place slowly – or at least, took place slowly in the past. The ice ages came and went over thousands of years. Plants, with the distribution mechanisms of their seeds, were able to move around, to get to the places where they were capable of growing and flourishing. Some did indeed go extinct, as a result of these fluctuations, when they got hemmed in, in places from which they could not easily disperse. But they were replaced by new species that were able to adapt and change to the new conditions. Again, this is because the changes took place fairly slowly, giving them time to adapt and evolve.
The challenge we face now is that human-created changes to habitats and the environment are happening much faster than the historic natural changes – too fast for many or most plants to cope with. Even where changes are slow, our activities are making it difficult for plants to ‘move’ the way they used to. Natural habitats have become fragmented – they remain as ‘islands’ in a sea of cities, towns and other human settlements, mines, factories and farms. If living conditions in one such ‘island’ become unfavourable for a certain species, it can’t easily disperse to a new place, because of all the fragmentation. Relocation is often not possible, because the plant’s seeds are adapted for short- or medium-distance rather than long-distance dispersal, leaving a species vulnerable to extinction.
Human-caused climate change is a big threat. Apart from rising sea levels, the major challenge is that the world’s climatic zones will change. Some places will get warmer, some places a lot warmer. Most plant species are specifically adapted to certain temperature ranges. Too cold, or too hot, and it is no longer possible for them to flourish. Consider a plant that only grows on cool mountain slopes (bearing in mind that, the higher the altitude, the colder the local climate). If the climate gets warmer, the plant can adapt by spreading to higher slopes where it is cool enough, but once the plant has reached the mountain’s peak, there’s nowhere higher and cooler to move to.
Hotter climates may favour insect pests and fungal or other diseases, which can ravage plants on a large scale. We know little about this, how to predict it, or how to counter such a problem.
The increased levels of carbon dioxide in the atmosphere, that is the main cause of global warming, also favours the growth of woody plants over grass, and may lead to grasslands converting into forest or shrublands. Many specialized grassland plant (and animal) species might face extinction.
A large change in atmospheric temperatures may seriously alter ocean currents and the circulation of the air across the planet. We cannot predict the full consequences, but certainly, big changes will happen. Imagine a desert region becoming a lot wetter. Under natural conditions, where plants are free to spread, new species will colonize the desert, but with restricted dispersal because of human-made barriers, it may be hard for suitable plants to establish themselves. As it gets wetter, the desert-adapted plants decrease – these plants cannot tolerate wet conditions – and with few or no new plants moving in, the desert could actually become more barren, with heavy rains washing away the soil.
Plant cover and plant roots protect the soil surface of the planet. Plants play a role in moderating the climate. The rainforest plants of the Amazon basin, for example, is partly responsible for the moist climate it needs to flourish. Trees release moisture over the canopy that in turn aids the formation of clouds that bring more rain. If you take away the forest – suddenly the local climate becomes drier and more extreme.
South Africa, as a result of global climate change, may end up a lot hotter and perhaps also a lot drier than it is right now. Plant cover and species diversity is likely to be adversely affected.
In the face of these severe challenges, we might become despondent – but humans are capable of doing incredible things, we just need to put in the work. With plants, this means leg-work. It is vital that we catalogue our plant diversity. At the moment we are just scratching the surface; vast parts of our country are still unexplored. We need volunteers, people to go to places and record the plants that are there. We need to know which ones are where, and which ones are rare. Finding a rare species out in the wild is a thrill; plant-seeking excursions are like treasure hunts. We need the knowledge to inform our conservation efforts. Many threatened plant species could recover and thrive with just a little bit of help from people. Growing plants is generally much easier than breeding mammals or birds. We can help species to relocate; we can boost denuded populations. So let’s spread the word and get working!
