Biodiversity in your backyard
Apart from the roles they fulfil, insects are fascinating and can add a splash of colour to your garden. Insects that warrant a closer look include butterflies, dragon- and damselflies, lacewings, fruit beetles, dung beetles, parasitic wasps, grasshoppers and praying mantises.
One of the major threats to biodiversity is invasive alien organisms. Start making a contribution by removing invasive alien weeds from your garden, such as this Queen of the Night.
It is possible to attract owls to your garden by hanging up owl nest boxes.
There is no reason why anyone should plant alien species in the garden. South Africa is blessed with an enormous diversity of plants and trees, many of which are highly attractive ornamental species.
Dr Ed Stam, Ecologist, NZG
Many of our readers would probably associate the word 'biodiversity' with National Parks, the tropics, the Great Barrier Reef, the Fynbos and other well-known biodiversity hotspots. These places are famous for their large numbers of species (i.e. high biodiversity), and protecting them surely contributes largely to biodiversity conservation.
However, this does not mean that the Earth's biodiversity is well protected. Currently, protected areas cover about 12% of Earth's land surface (see www.wdpa.org), which is a relatively small proportion of the total. This means that many species do not occur in protected areas or are much more abundant outside of those areas.
Furthermore, the network of protected areas consists of several relatively small and isolated snippets of land. Many populations in these small reserves are not viable in the long run if there is no exchange of individuals with other populations, either from other reserves or from unprotected areas. This means that for biodiversity conservation to be effective it is necessary that we also look at unprotected areas including farmland and even urbanised areas. It is the latter on which we will focus in this article.
Biodiversity in the suburb
Even if you live in a suburb you can do your bit to contribute to biodiversity conservation, especially if you have a garden. One of the major threats to biodiversity everywhere is invasive alien organisms. You can start making a contribution by removing invasive alien weeds from your garden, such as Jacaranda and Syringa trees, Poplars, Lantana, Queen of the Night, Prickly Pears, Morning Glory and Cat's claw creeper (see www.dwaf.gov.za/wfw/Control for more information).
A step further would be to garden with indigenous plant species only. There is no reason why anyone should want to plant alien species in the garden. South Africa is blessed with an enormous diversity of plants and trees, many of which are highly attractive ornamental species. Furthermore, if you choose local species there is no need to water them profusely or use so many fertilizers.
An added advantage to using indigenous plant species is that they are more attractive to local animal species, as the latter have co-evolved with them. Many insect species, in particular butterflies, are highly specialised in the food plants they select. To an extent, gardeners can determine which species frequent their garden by choosing plants that attract them. This applies to insects as well as birds.
The importance of insects
Insects are often associated with pests, but only a small proportion of insects are pest species. Others fulfil important roles in the garden, such as pollinating flowers, decomposing leaf litter and… controlling pest insects (e.g. ladybird beetles feed on aphids).
Insects form by far the most diverse group of animals, which means that making your garden "insect friendly" is in itself the most efficient way to enhance biodiversity in your backyard. In addition, insects are food for other animals such as spiders, frogs and toads, lizards, skinks and geckos, insect-eating birds and small mammals such as shrews and hedgehogs.
Lastly, apart from the roles they fulfil, many insects are simply breathtakingly beautiful and fascinating and can add a splash of colour to your garden. Butterflies are the obvious example, but there are other insects that warrant a closer look, such as dragon- and damselflies, lacewings, fruit beetles, dung beetles, parasitic wasps, grasshoppers and praying mantises, to mention a few.
Butterflies in particular are very choosy about where they lay their eggs. Most species will only use a few, or only one, 'host plant' species. This makes butterflies very vulnerable to extinction. By gardening with locally indigenous plants we can help protect them.
Given the riches that butterflies and other insects can bring to your garden, it pays to tolerate some insect damage to your plants rather than to use insecticides to prevent insect damage. Indigenous plants have evolved their own defence mechanisms against local species of insects and they do not need us to assist them with chemicals that kill everything that crawls.
Compost and mulch
Biodiversity does not only occur in places where we can see it. There is a whole world of diversity of which few people are aware - the community of organisms that live in the soil. Healthy soils are brimming with life. There are earthworms, millipedes, centipedes, woodlice, crickets, scorpions and pseudo-scorpions, slugs and snails, beetle larvae and spiders.
Many of these organisms fulfil important functions in the soil. Earthworms, millipedes and woodlice, for instance stimulate decomposition by fragmenting organic matter into small particles, making it more accessible to micro-organisms. Furthermore, earthworms improve the structure of your soil by digging tunnels and mixing the organic matter with sand and clay particles, giving it a granular aspect. This enhances both drainage and aeration of the soil, which in turn stimulates root growth.
The way to enhance the diversity of soil organisms is by mixing a lot of compost into the soil and covering it with mulch. By mulch we mean any kind of organic matter that comes down from the trees, be it leaf litter, flowers, fruits, seedpods, bark, twigs or even rotting logs. A thick layer of mulch (± 5 cm) provides a good habitat for the many soil organisms mentioned above. Moreover, it dampens fluctuations in soil temperature and moisture content and prevents 'crusting' of the soil. A nice thick litter layer is also irresistible to thrushes and Cape robins, who love to turn the leaves in search for tasty morsels.
How to lure birds to your garden
We can roughly divide the common garden birds into seven functional groups, which all have different requirements. These are insect eaters, seed eaters, fruit-eating birds, water birds, nectar feeders, mixed feeders and predatory birds. Obviously, you will get the highest diversity of birds in your garden if you can provide for all of these groups. We will discuss each of the groups one by one.
Insect-eating birds form a large group which includes thrushes, robins, warblers, shrikes, flycatchers, white-eyes, chats, barbets, woodpecker, hoopoes, woodhoopoes and more. Your garden will attract more of these birds the more insects there are. How to attract insects to your garden has already been discussed above.
It helps to have many flowers that attract bees and other pollinators. Some of the trees and shrubs that fit this purpose are all Acacias, the coral tree (Erythrina lysistemon), tree fuchsia (Halleria lucida), weeping boerbean (Schotia brachypetala), buffalo thorn (Ziziphus mucronata), wild pear (Dombeya rotundifolia), Cape honeysuckle (Tecoma capensis) and wild honeysuckle (Turraea floribunda). Other excellent flowering plants are the Aloes, especially as they flower in winter when there are few other resources for insects.
Some trees are yearly defoliated by hordes of caterpillars, which in turn are feasted on by cuckoos. Examples are the rock alder (Canthium mundianum) and the wild peach (Kiggelaria africana), the host plant of Acraea caterpillars.
We already mentioned the importance of mulch as a rich resource for insect-eating birds. Another tip worth considering is to leave some dead branches on your trees to attract woodpeckers, woodhoopoes and barbets.
Examples are the beautiful waxbills, finches, firefinches, canaries and bronze manikins. These are best attracted by leaving some tufts of grass to grow tall enough to set seed. Seed-eating birds frequent most grass species. Attractive grasses for the garden are Melinis nerviglumis, Panicum ecklonii, Panicum maximum, and Phragmitis australis. Ideal would be to have several species that flower in different seasons, so that there is seed available throughout the year. Alternatively, you can also attract seed eaters to your garden by offering bird seed on a feeding platform.
Mousebirds, turacos, parrots, barbets, bulbuls, hornbills and pigeons form part of this group. They are obviously attracted by fruiting trees, of which there is a wide variety. To mention a few - all indigenous fig trees, the tree fuchsia (Halleria lucida), Transvaal red milkwood (moepel, Mimusops zeyheri), sourplum (Harpephylum caffrum) and white stinkwood (Celtis africana) all produce highly attractive fruits and berries in abundance.
To attract some of the larger water birds you would need a large pond which, in turn, requires a large garden. However, the hugely attractive kingfishers are also attracted by small to tiny ponds. Even if there is no fish in it they will still perch near it for a while to check it out.
Best known in this category are, of course, sunbirds and sugar birds. However, they are not the only birds that like nectar. Cape white-eyes, for instance, make small holes at the bottom of flowers to get to the nectar. Good nectar-producing species are the coral tree (Erythrina lysistemon), Cape honeysuckle (Tecoma capensis), red-hot pokers (Kniphofia praecox), proteas, pincushions and all aloes.
Many of the birds which are placed in one of the aforementioned categories actually belong to this group. For instance, sunbirds eat insects too, hornbills eat fruits and the seeds of acacias, pigeons eat insects, worms and fruits, and sparrows and starlings are born opportunists. The placement in these categories is not absolute; it rather serves to provide a guideline for gardeners who want to attract a variety of birds to the garden. If all of the above-mentioned resources are present, you will obviously also get the mixed feeders.
One group of predatory birds that live in close association with humans is the owls, in particular barn owls and spotted eagle owls. It is possible to attract owls to your garden by hanging up owl nest boxes. Apart from being fascinating creatures, owls are extremely efficient controllers of rats and mice. The Endangered Wildlife Trust (EWT) has published a brochure on how to build owl nest boxes which is freely available.
Apart from food and water resources, vegetation structure is also an important factor in bird diversity. Some species prefer the tree tops, while others like to roam around in the undergrowth. Some like dense thickets, while others prefer more open vegetation.
Another point to consider is the nesting habitats that different bird species prefer. There is no space for an extensive discussion of this, but worth mentioning is that many bird species like to nest in acacias, probably because the thorns provide them with some protection. The author has a large fever tree in the garden which is very well liked by the local Southern masked weavers.
Biodiversity conservation is not limited to erecting fences around protected areas. Everybody can contribute to the protection of local species albeit on a smaller scale.
One characteristic of species diversity is that it is scale dependent. This means that the larger an area is, the more species it can sustain. The practical consequence of this is that you can expect to see even more species in your garden if you can convince your neighbour to go the indigenous route. And your neighbour's neighbour, and so forth until the whole neighbourhood is converted. An indigenous gardening competition may be a good motivator. If you are a member of a ward committee, you are in a good position to spread the message. It is worth the try…
Botha, C. & Botha, J. 2002 Bring nature back to your garden. Wildlife and Environment Society of South Africa (KwaZulu-Natal branch)
Bruzas C. & Bruzas A. 2001 Wildlife on your doorstep. Wildlife Society of Southern Africa (Natal Branch)
Joffe, Pitta 2001 Creative gardening with indigenous plants: A South African guide. Briza, Pretoria
Joffe, Pitta 2003 Easy guide to indigenous shrubs. Briza, Pretoria
Trendler, R. & Hes, L. 1994. Attracting birds to your garden in southern Africa. Struik, Cape Town.
On alien invasive plants
Henderson, Lesley 2001 Alien Weeds and Invasive Plants - a complete guide to declared weeds and invaders in South Africa. ARC, Pretoria
www.dwaf.gov.za/wfw/Control - the official alien weed control site of the Working for Water programme