Galapagos Islands flora - Island plantlife
The Galapagos Islands have a rich diversity of plant life. In the highlands bromeliads, orchids and the endemic Scalesia or tree daisy can be found, while along the coasts giant prickly pears, and incredible candelabra cacti thrive. The islands also have several endemic species such as their own cotton, tomato, pepper plants.
The plant life of Galapagos is just as extraordinary as its wildlife, although it has received less attention and publicity. There are many threats facing the vegetation, however, and world attention is currently focussed on raising funds for botany campaigns to safeguard endangered species and control the many invasive plants introduced to the islands by humans.
The native flora
There are about 560 native species of plants in the islands, in other words, plants which arrived in the islands by natural means. Of these, almost one third are endemic to the islands, meaning they are found nowhere else on earth. For example, Galapagos has its very own, endemic species of cotton, pepper, guava, passion flower and tomato. Not only that but many species are so different from others elsewhere that they are grouped in their own endemic genera. These include Scalesia, the endemic 'daisy tree', which has evolved into a whole host of different species in a direct botanical parallel of the Darwin's finches. Other endemic genera in the daisy family are Darwin's aster Darwiniothamnus, the cut-leaf daisy Lecocarpus and needle-leaf daisy Macraea. There are also some endemic genera of cacti, Brachycereus, the lava cactus and Jasminocereus, the candelabra cactus.
On the whole, Galapagos plants tend to be 'pioneer' species, hardy plants which successfully cross oceans and manage to establish themselves in the often hostile environment of islands. Because relatively few plants succeed in doing this, the flora is 'depauperate' - there are far fewer species here than in similar environments on the South American mainland. Plants are also adapted to having very few insects or other animals to pollinate their flowers or disperse their fruits and seeds. This means there are few big, showy flowers to attract pollinators and few specialised fleshy fruits. But there are some fascinating relationships between plants and animals. The giant tortoises and land iguanas, for example, feed on Opuntia, the prickly pear cactus, and have influenced its growth form on different islands.
One of the biggest problems in Galapagos comes from foreign plant species introduced to the islands by people, which then become pests and invade the native vegetation. Most of these species were brought on purpose either for agriculture or gardens, and the problem is therefore greatest on the inhabited islands. There were 475 known introduced species by early 1999 and the process is still continuing at the rate of about 10 new arrivals each year. At the current rate, it is estimated that introduced plant species will outnumber native species by the year 2007. About 40 of these are already seriously invading the native vegetation and another 70 introduced plants are likely to cause problems in the future.
Different introduced plants are problems on different islands around the archipelago. On Santa Cruz island, for example, the worst culprits are guava Psidium guayaba, the curse of India Lantana camara, a species of blackberry Rubus niveus, and quinine Cinchona pubesceris. Quinine trees have invaded a unique vegetation zone formed by the endemic plant Miconia robinsoniana, which is found on only two islands. Quinine shades out Miconia and eventually all the other plants around it, so if not controlled it could completely wipe out this whole zone. The guava tree, being drought-resistant, can invade just about anywhere, replacing native trees and shading out all the smaller plants underneath. The endemic Scalesia tree dies out in huge numbers during severe El Niño events and there are fears that it will never recover from the 1997-98 event, as the introduced guava will prevent its natural regrowth. Other problem plants are passionflower, elephant grass, and kalanchoe, the ornamental mother-of-thousands.
Introduced animals also have a detrimental effect on the native flora. Goats have decimated the vegetation on many islands and brought some plant species to the verge of extinction. Feral donkeys and cattle also graze on native plants or trample them. Insects and other invertebrates are also a major problem. For example, in 1982 a scale insect, the cottony cushion scale, was first reported in Galapagos and spread to another seven islands by 1997. It infests and often kills many kinds of native plants, and scientists looked at biological methods of control to safeguard the vegetation. In January 2002 the Australian ladybug, the natural enemy of the cottony cushion scale, was released following extensive studies to ensure that the ladybug did not pose any threat to the Galapagos ecosystem.