Academic Reading — Test 146

Reading passage

Along the southern and south-western edges of South Africa lies a botanical region unlike any other on the continent. Known as the fynbos, this belt of low, shrubby vegetation covers a relatively small area, yet it harbours an extraordinary concentration of plant life. Botanists estimate that around nine thousand plant species grow there, and roughly two-thirds of them are found nowhere else on Earth. Such species are described as endemic. The fynbos forms the heart of the Cape Floristic Region, which despite its modest size is recognised internationally as one of the planet's most important centres of plant diversity. The richness of this flora, however, is matched by its fragility, and a growing number of fynbos species are now classified as threatened. The pressures on the fynbos are many. Expanding cities, vineyards and farmland have steadily replaced natural vegetation, fragmenting the landscape into ever smaller patches. Invasive trees and shrubs introduced from other parts of the world, particularly certain Australian acacias and pines, crowd out native plants and consume large quantities of groundwater. A further complication is fire. Fynbos is naturally adapted to burn, and many of its plants depend on periodic fires to trigger germination or to clear space for seedlings. Yet when fires occur too frequently, or at the wrong time of year, slow-maturing species may be destroyed before they have produced a new generation of seed. Climate change adds yet another layer of uncertainty, since shifts in rainfall and temperature may push some species beyond the conditions in which they can survive. Faced with these threats, conservationists have turned increasingly to seed banking as a way of safeguarding the region's botanical heritage. The principle is straightforward. Seeds are collected from wild populations, carefully cleaned, dried to a low moisture content and then stored at sub-zero temperatures, typically around minus twenty degrees Celsius. Under such cold, dry conditions the seeds enter a state of suspended animation in which their living tissues remain viable, sometimes for many decades. A single well-managed collection can therefore preserve the genetic material of a species long after the original plants have vanished from the wild. Seed banking is comparatively inexpensive, occupies little space, and allows enormous numbers of species to be conserved within a single building. The work is far from mechanical, however, and it demands considerable botanical skill. Collectors must time their visits to coincide with the brief period when seeds are ripe, a window that may last only a few days and that varies from one species to the next. They must also gather material from a sufficient number of individual plants to capture the genetic variation within a population, rather than relying on the seed of a single parent. Once in the laboratory, each batch is tested to confirm that the seeds are alive and capable of growing. This is commonly done through germination trials, in which a sample is encouraged to sprout under controlled conditions. Some fynbos seeds germinate only after being exposed to smoke or to chemicals found in smoke, a reflection of their fire-driven ecology, and researchers must reproduce these cues artificially in order to wake the seeds. Not every species, unfortunately, can be rescued in this manner. A minority of plants produce what are termed recalcitrant seeds, which cannot tolerate the drying and freezing on which conventional banking depends. For these the seed bank offers no refuge, and alternative methods such as cultivating living collections in botanical gardens, or freezing tissue in liquid nitrogen, must be considered instead. Even for species that do store well, a seed bank is not a permanent solution in itself. Stored seeds gradually lose their vigour, and a collection must eventually be grown into mature plants so that fresh seed can be harvested and banked once more. Conservationists therefore regard seed banking not as a substitute for protecting habitats but as an insurance policy that buys time. That insurance has already proved its worth. Seed drawn from banks has been used to re-establish fynbos species on land cleared of invasive trees and to bolster small wild populations that were in danger of disappearing. Material held in storage also supports scientific research into how these remarkable plants reproduce, respond to fire and might adapt to a warmer future. Perhaps most importantly, the very act of collecting seed forces botanists to survey the landscape and to record where rare species still cling on, generating knowledge that guides wider conservation efforts. For a flora as rich and as endangered as that of the Cape, the humble seed, sealed in its frozen vault, has become one of the most powerful tools available for ensuring that future generations inherit the full diversity of the fynbos.