The plant kingdom’s great richness is in severe danger of becoming drastically degraded as a result of man’s activities. At least 25,000 species, comprising around ten percent of the world’s flora, are believed to be threatened with possible extinction or to be dangerously rare. This figure is all the more serious when one realizes that man depends totally on the plant kingdom for his basic needs of food and oxygen, as do all other animals, and that plants provide timber, numerous drugs and a host of other incredibly varied products. In addition he delights in the charms and attractions of numerous widely differing species, both in the wild and in the garden.
There is a terrible finality about the extinction of a species. As with the dodo of Mauritius, once gone it is lost for ever and its unique set of characters cannot be reconstituted. With plants the situation is all the more tragic since many species may become extinct before their possible value is known; the economic potential of so few plants has been investigated and man has made use of only a minute fraction of the plant kingdom. Modern research is constantly discovering new products in obscure and little known plants. For instance, theof Simmondsia chinensis, a shrub known as jojoba, contain an oil recently found to be a substitute for the precious oil only previously known from the endangered sperm whale. It may well be of great economic value in the future. Many of the estimated 25,000 threatened species may have similar potential; their loss would be an inestimable tragedy.
The best way of looking at the threats to plants is to consider a few examples of threatened floras, in particular three that are probably the most in danger: those of tropical rain forests, of islands and of the countries of the arid zone. These are only a selection of threatened habitats and areas but it may help to stir concern for man’s most precious resource —the cornucopia of the plant kingdom.
The tropical rain forests of the world are becoming seriously threatened and there is concern over their future. These evergreen forests occur in areas with a tropical climate with rain throughout the year and little or no seasonality. They are the principal vegetation in coastal West Africa and in the Congo basin, in South-cast Asia from the Malay Peninsula through the islands of Sumatra, Java and Borneo to New Guinea and the Philippines, and in South America reaching from the foothills of the Andes across the vast Amazon basin up to the Caribbean and parts of Central America.
These forests are perhaps the most luxuriant and magnificent vegetation on earth, teeming with plant and animal species in an endlessly changing continuum and are especially interesting for the botanist for their small isolated pockets of very local species. At the other end of the scale, many rain forest species have unusually scattered distributions, occurring in large overlapping areas at a density of only a few individuals per square kilometre.
The forests are particularly rich in climbers, palms and epiphytes—in particularand in South America and orchids in Southeast Asia. There are believed to be 3,000-4,000 species of orchids alone in the area from the mainland of Malaya to New Guinea. This is a remarkable figure —more than twice the whole flora of the British Isles.
Rain forests are also of great significance since, with the exception of areas too inhospitable for human settlement, they are the only type of vegetation of which large tracts remain, or did until very recently, untouched by man. Evolution in some rain forest areas may have continued uninterrupted under favourable climatic conditions since thefirst evolved. Despite the immense problems in allocating land use to provide food for fast-expanding human populations, it is vital to preserve at the very least large intact samples of such forests so that the processes of evolution can continue.
The insatiable world hunger for wood is a major threat to the rain forests, especially in the countries where the finest timber trees, especially the Dipterocarpaceae, are found. In West Malaysia, at current rates of extraction, present trends indicate that all the lowland dipterocarp forest outside forest reserves and pro- tected areas will have been exhausted within the next ten years. For example, it has been estimated that 2 sq km (0.8 sq mile) of lowland dipterocarp forest per day passes over the causeway from Malaya into Singapore for export. Another example is of 172,000 hectares (425,000 acres) in the Philippines lost every year. Further threat comes from new technology to remove not only the logs but virtually the whole vegetation for chipboard. Unlike a temperate forest, most of the nutrients in a rain forest are tied up in the vegetation rather than the soil and so removal of the plant cover can result in loss of soil fertility, especially in upland areas.
In the Amazonian rain forests the principal threat to the flora is the uncontrolled utilization of the forest following the opening up of the area for development. In an effort to expand the potential of the region, huge road-building projects are underway, such as the 5,619km (3,510 miles) Transamazonica Highway from the Atlantic to Peru. The scale is immense and the aim is to use much of this vast area for commercial exploitation in terms of minerals and agriculture. On both sides of the roads, vast estates are being cleared for cattle-ranching. However, little of the Amazon soil is likely to be suitable for agriculture; within a few years the quality of the grazing will decline rapidly. On plots cleared for food-crops, the decline in soil fertility, the increasing weeds and the burgeoning insect pests, all associated with peasant agriculture, are tending to lead to degradation of the land. Ignorance and lack of fertilizers are crucial factors.
The flora of the Amazon region is probably the least explored anywhere in the world and numerous species are doubtless being lost before they can be discovered. Rain forests in South
America, when severely disturbed on a large-scale, may not regenerate. When exploited in this way, the forest becomes a non-renewable resource like coal or oil, but one in which the diversity of its renewable components is being inexorably lost.
There are abundant reasons why conservation is necessary. Strong arguments centre round the value of the upland forest in maintaining water catchment and preventing soil erosion. The production of hardwood timber is also important since there will always be a demand for the quality hardwoods despite the great pressure for paper, chipboard and similar products. But the foremost argument is that the rain forests, in all their luxuriance and diversity, represent a gene-pool of inestimable value to man.
The potentials of the great majority of the plants have never been explored and many could well prove to be of vital importance in the future, either as crop-plants in their own right or as material for use in crop-breeding. For example, the Southeast Asian forests are particularly rich in trees with edible fruits, but only two species of the genus Durio are in cultivation out of 19 species in Borneo, most of which have delicious fruits. No known work on breeding has been done. Of the mangoes, only Mangifera indica is widely cultivated and bred. Other species in the genus have only been grown very locally, although some are excellent, such as one from a small area of Borneo which has fruits as large as a coconut. Similar situations exist for plants producing oils, drugs and all manner of useful products. In addition there are numerous species of interest to botanist and visitor, like the giant Rafflesia arnoldii, an extraordinary parasite with the largestin the plant kingdom which is now becoming very rare because of habitat destruction. However the loss of the forest is not only the loss of a uniquely valuable set ot organisms—it is also the loss of a whole community, in this case the most prestigious and exciting ecosystem on this planet; composed not only of plants but of animals of every kind which cannot exist outside it.
Island floras, especially in the tropics and sub-tropics, are in particular hazard. The plants whose survival is threatened are mostly the endemics (I.e. confined to the island concerned). These endemic species may have evolved on the island or may be old relicts of formerly widespread species which have died out elsewhere. In either case, because of their isolation from outside evolutionary pressures, they are particularly susceptible to grazing from introduced animals and competition from vigorous introduced plants.
Consider the flora of Socotra, a dry island 225km (140 miles) east of the Horn of Africa, Cape Guardafui in Somalia. It has been known since antiquity as a source ot dragon’s blood, a red dye produced fromspecies. From a total of about 600 species of flowering plants, 216 are at present believed to be endemic. As a result of grazing by excessive numbers of livestock, at least 85 of these are in immediate danger of extinction. The flora has presumably evolved partly in the absence of large mammals, unlike the flora of the African mainland, and few species have characters such as spines which act as a defence against grazing animals. Hence they are particularly susceptible to the ubiquitous goats. In 1880 Professor I. B. Balfour on a botanical expedition to Socotra found the prickly Lasiocorys spiculifolia to be ‘one of the plants which makes progress over many parts of the plains unpleasant’. However, in 1967 the vegetation on the coastal plains had become so degraded that only a single individual of this species was found on the whole island.
In many cases the species concerned are of great importance or interest to man. The only species in the pomegranate family other than Punka granatum (the cultivated pomegranate) is a small tree endemic to Socotra called Punica protopunica. In 1967 only four very old and widely separated trees were seen and when these trees die, it will probably become extinct in the wild. The goats prevent any regeneration by eating any youngthat may come up. Near relatives of crop plants are extremely important to man since they may be needed for breeding factors such as resistance to pests and diseases into the cultivated varieties. Another endangered Socotran species is Diraclima soco-trana whose flowers are so distinct and unusual that the species has been given a family of its own, the Dirac’hmaccac. In 1967 it was reduced to a grove of about 30 trees with no regeneration and unfortunately it is not in cultivation. Its extinction would represent a major loss of diversity in the plant kingdom.
The island of St Helena in the South Atlantic is another example showing the catastrophic effects of introduced plants as well as grazing animals. Goats were introduced in 1513 and within 75 years there were sightings of herds 2km (1.2 miles) long on this small island. They devastated the native torests. The island was explored botanically for the first time in 1 805-10 when the forests had already been reduced to a few patches, high up on the central ridge. About 31 endemic species are known, of which 1 1 are extinct. However the great Victorian botanist, [. 1). Hooker of Kew, estimated that there must have been about 100 endemic species in this ‘wonderfully curious little flora’ before man intervened. These plants will never be known.
The goats have now been controlled and the principal threat is introduced plants such as New Zealand flax, Phormium tenax, and gorse, Utex europaens. These are spreading rampantly through the small patches of relict forest. Since the flax industry declined, the crop has not been cut and so the plants have seeded abundantly. Since flax is about 3m (10ft) tall. it swamps small endemics such as Wahlenbergia linijolia, a low shrub with delightful white bell-flowers close to Campanula.
Similar scenarios can be spelt out for numerous islands, particularly those in the Indian and Pacific Oceans. Mauritius, the Seychelles, Sri Lanka, the Marquesas Islands and the Juan Fernandez islands may sound like tropical idylls, but similar botanical tragedies have happened there. The Juan Fernandez Islands, the home of Robinson Crusoe, lying off the coast of Chile. are particularly badly damaged due to introduced sheep, cattle, horses, goats, rabbits, rats. and plants such as Aristotelia and lhihits (bramble). On- many islands goats and other mammals were introduced by mariners several hundred years ago so that there would always be fresh meat available for passing ships. The effect on the plants has been catastrophic.
Pressures on land for tourist developments, for agriculture and for forestry are of course particularly acute on islands because of the problem of size. In the Canaries, with about 500 endemic species of flowering plants, wide-scale clearance of hill land for agriculture is having a disastrous effect on the flora. The Canaries are the home of a very special vegetation, the laurel forests, which have many endemics. They are the only areas on the island which remain moist throughout the dry Mediterranean summers and they play an important role in condensing moisture from the clouds as well as preventing erosion on steep slopes. Removal of the laurel forests and excessive coppicing of the trees for poles and firewood results in erosion damage and the streams lower down the hillsides dry up in the summer. The destruction of this community has now gone so far that even the constituent trees such as Arbutus canariensis are threatened plants.
One of the saddest cases ot all is Hawaii. It is estimated that 96.1 percent of the plant species that occur on the Hawaiian Islands are endemic. This is an extraordinarily high percentage, reflecting the situation of the islands as a ‘laboratory of evolution’. Two hundred and seventythree species are listed as extinct and 800 as endangered—and the list is by no means complete.
The islands are volcanic and many species tend to be restricted to a few islands of vegetation called kipukas, surrounded by lava flows. Many have become greatly depleted by lava flows in the geological past, and have entered the era of man already very rare and hence especially vulnerable to the grazing and habitat destruction which followed. For example,
Hibiseadelphus has flowers like those of a, but by failing to open completely are adapted for by endemic birds of the nectar- Drcpaniidac, the Hawaiian honey-creepers, with bills fitting the slight curvature of the corollas. It is thus a fascinating example of closely linked evolution between plant and animal endemics. However all the Hibiscadelphus species and most of the honey-creepers are cither endangered or extinct and it is uncertain whether one can survive for long without the other.
In many countries ot the arid and semiarid zones, overgrazing by domestic livestock is having a catastrophic effect on the vegetation, in places reducing pasture to desert and semi-desert as, for example, has happened in the belt from Western Asia to the Sahcl in Africa.
The effects of overgrazing on vegetation are complex. Since animals are selective in their feeding habits, the composition of the flora gradually changes. Goats, sheep and cattle all have somewhat different effects and so the proportion of the various animals in the herd is significant. Goats in particular eat virtually anything and so prevent regeneration of nearly all the flora. However, despite the differences, a common pattern often emerges. Firstly the palatabletend to become eaten off and the grasses reduced. The trees cannot regenerate and for firewood and timber may accelerate their decline. At this stage the soil may begin to blow. Eventually even the few bushes that are left and even the unpalatable plants such as aloes may disappear as the land becomes a desert or semi-desert.
For example, on the Red Sea Hills of Ethiopia and the Sudan, the distinctive palmlike tree,ombet of the Agave family, is now drastically reduced. It was formerly a main component of the scrub covering these extensive hills, but all the plant life over vast areas has been eliminated and only occasional and scattered trees remain, surrounded by bare rock. The ombct’s decline was hastened by the removal of the trunks for firewood and the for making mats and baskets.
In most cases it is not yet known which plants are threatened. Many countries such as Turkey and Iran have particularly rich floras. Elsewhere the floras are not so well known and few have been looked at in terms of conservation. but in 1972-3 an expedition to Somalia aimed to do just this. Many species were found to be on the verge of extinction, especially the endemics which are believed to make up as much as 30 percent of the flora. The results of overgrazing were very extensive, especially in the north where visitors in the nineteenth century had found a country with parklike vegetation of scattered trees and abundant grass, typical of much of East Africa. There was much game, a valuable source of meat.
Today this same area is one of the most degraded and few trees are left. The last elephant was said to have died in 1953. Large areas are now dominated by species such as Aloe megala-cantha which is unpalatable to stock and marks one of the last stages in the formation of deserts and semi-deserts. Indeed the whole country has been overgrazed to some extent and the carrying capacity of the land greatly reduced. The main wealth of the Somalis lies in their grazing animals so the situation for the country is very serious. The political and human problems caused are overwhelmingly difficult, but it is clear that the present overstocking is a course for disaster. The vegetation of the arid and semiarid zones is one of the most fragile ecosystems in the world and is very susceptible to permanent damage from overgrazing.
Threatened European species
In contrast the European flora is not so seriously affected as most of the tropical floras. Nevertheless there are about 1,000-1,200 species in Europe that are threatened or very rare. Many are cliff or mountain species which are only known from a few localities, often fairly inaccessible and so not under immediate threat.
The main risk comes from unscrupulous collectors in many cases, and it is felt that some form of protection and monitoring is desirable to safeguard their futures. The devastation of the vegetation of so much of the Mediterranean coasts by developments for tourism has not had too serious an effect on the flora so far since most of the coastal species are widespread, often occurring both in North Africa and Europe. A rather unusual exception is Phoenix theophrasti, the Cretan date palm, which is confined to one river valley leading down to the sea in Crete and a few other scattered localities on the island. As the only palm grove in Europe, the site is a major tourist attraction and the palms are beginning to suffer.
In northern Europe the main group of species that are threatened on a continental scale are the aquatic and wetland plants such as the spectacular insectivorous plant, Aldrovanda vesiculosa. Drainage, pollution and infilling have taken their toll on these vulnerable aquatic habitats. In contrast most of the orchids, which are generally thought of as becoming very rare as indeed they are in Britain, are frequent in many countries of southern Europe. The exception is of course that most handsome of orchids, Cypridedium calceolus, the lady’s slipper, which has been over-picked and uprooted for planting in gardens. Although it grows from Europe through Russia and China to the USA it has become very rare, at least in most of Europe. In Britain only one zealously guarded clump remains.
Protection of threatened species
On a world scale, some collectors are a major threat to certainof plants such as tropical orchids and succulents which are keenly grown by many amateurs. In Mexico some have been brought to the verge of extinction by commercial raiders. The export of orchids from Southeast Asia is also believed to be considerable. When such a plant becomes rare by natural causes or by habitat destruction, the threat from collectors intensifies since rare plants are considered particularly desirable and fetch high prices. The result is a vicious circle which results in extinction.
A number of countries have strong laws protecting their flora but enforcement is difficult, especially in the tropical countries with such rich and varied floras. Fortunately international action is being taken which may case the situation. In 1973, 57 nations signed the Washington Convention on International Trade in Endangered Species of Wild Fauna and Flora. By a licensing scheme this aims to monitor, and in some cases control, the international trade in a given list of plants and animals. There are of course facilities to allow legitimate transfer of plants between scientific institutions and to encourage cultivation in large numbers by nurserymen so that the pressure can be taken off wild populations. This is a great step forward.
What can be done about the great majority of threatened plants, those threatened by grazing, forest destruction or similar causes? The best solution is to protect the habitat and so conserve the plants and animals it contains. Cultivation in botanic gardens is a valuable ‘long-stop’ against final extinction but it is no long-term solution. The formation of National Parks and Nature Reserves to cover large samples of all types of vegetation and to include as many threatened species as possible is an urgent task. The resulting profits from tourism can be considerable, although of course it is very difficult to maintain large wilderness areas intact and free from human settlement, especially where poverty is involved; management must always be related to the needs of the local people. Nevertheless where only small fragments of unique vegetations remain, absolute protection is essential, although it is uncertain how far islands of vegetation in a sea of disturbed land can maintain themselves in the long-term.
In recent years the importance of reconciling conservation with development has received great interest. In Britain this has involved, for example, re-creating habitats for wildlife on small patches of wasteland, leaving aside small areas of trees from the plough, allowing undergrowth to develop in commercial forests. Above all it implies an awareness of the wildlife around us and an understanding of their needs. But it is in the less developed tropical countries where it is so important to bring conservation and development nearer together.
There are very strong economic arguments for conserving vegetation and not just as small isolated areas. In theory this implies not protecting the resource from man, but using it on a fully sustainable basis at a level of productivity where none of the various components are lost. It is clear that many areas of over-exploited tropical rain forest, especially in upland areas, will not regenerate. Productivity may fall ‘and the damage may prove irreparable in some areas. It is clear that in arid countries overgrazing inexorably leads towards deserts and semi-deserts. Sadly, most of the countries in this criticalare the ones for whom dependence on the land is total and so failure to observe conservation may spell disaster.
It is for this reason that a major portion of the programme of the International Union for Conservation of Nature and Natural Resources (IUCN) on rain forests and arid lands has been to produce guidelines for development in collaboration with the countries concerned. At the same time, the recently formed IUCN Threatened Plants Committee is steadily building up information on which species are threatened throughout the world and where they grow, so that at least the information needed by decisionmakers will be available. Time is very short and the need for reserves and protected areas desperately urgent. Some species now threatened will undoubtedly be lost in the near future and all the time large areas of vegetation are being permanently ruined.
Aldo Leopard, the distinguished American conservationist, is reputed to have once said: ‘The first rule of intelligent tampering is to save all the pieces.’ This is perhaps the best justification for conservation of plants. It is of the very greatest importance to ensure that the renewable components of the world’s vegetation on which man depends, are conserved in perpetuity so as to be available for his future benefit.