Dear Readers, the most vulnerable habitats are often those on islands. This is because the flora and fauna there have often evolved in isolation, and so are endemic – they can be found nowhere else. They may be beautifully adapted to their local conditions, and may have lost things that they don’t need – birds may be weak flyers or flightless, for example. Animals may also have lost their wariness and be unafraid of humans. Plus, being on an island tends to limit population size because of food resources or space: there is literally nowhere else for an animal to go. So, many island species were never common, but they survived because there were few predators, or little competition.
An island also doesn’t need to be a literal ‘island’ surrounded by sea – we can think of many isolated valleys and mountain habitats as ‘islands’ too. The places where mountain gorillas live, for example, are virtual ‘islands’ because the animals are isolated in them, with no suitable habitat round about.
Animals and plants that are endemic to islands are often ‘inbred’ by our definition of the term – they have a small population, so have they little choice. But this doesn’t seem to be as much of a problem as you might think: in his book ‘The Song of the Dodo’, David Quammen describes how, over time, any genes that might cause problems have disappeared, because the individuals holding them have either died or been unable to breed. This is very different from the inbreeding that occurs in, for example, some pedigree dog breeds, or when a wild population becomes isolated from other members of its species by roads or other barriers.
In Madagascar, the ringtailed lemurs of the Berenty reserve are now completely cut off from other lemurs by roads and also because there are massive sisal plantations, which they will not cross. Ironically, the sisal is used for, among other things, degradable compost bags for folk in the West to wrap their kitchen waste in. Only time will tell how much of a problem the inbreeding that occurs as a result will be for the lemurs.
Ringtailed lemurs in Berenty, Madagascar (Photo Two)
So, in Hawaii and Galapagos, Madagascar and Mauritius, New Zealand and Australia, there are unique populations of animals who have evolved in isolation and who are superbly adapted to their original environment, but very vulnerable to change.
I guess we can all see where this is going.
My course book concentrates particularly on Hawaii, the most isolated group of islands in the world. Polynesians arrived there about 2000 years ago, and started to change the landscape – they brought up to 30 new crops, including coconuts, bananas and sugar cane, and animals such as pigs, goats and dogs. However, the population was never enormous, and although some land was cleared for agriculture there doesn’t seem to have been a major impact on the ecosystem. This has largely occurred in the past two hundred years, after European colonisers arrived, creating sugar plantations, taking over an entire island for the growth of pineapples, logging the forests for sandalwood and bringing in other new crops such as coffee and macadamia nuts.
The two greatest dangers to island populations are habitat degradation and the introduction of alien species that outcompete the indigenous flora and fauna. Hawaii has had both.
The scientist and author Richard Fortey writes about a walk in the forests of Hawaii in his book ‘The Earth – An Intimate History‘. Here is what he has to say.
‘Almost none of the plants that climb up the massive trees along the path are a native of O’ahu or the Hawaiian islands. Indeed, neither are the trees themselves. They are interlopers, brought to this remote place by humans. These plants settled in the tropics and thrived, displacing most of the native vegetation. The resemblance of the climbers decking the trees to pot plants is no coincidence: some of them are the same species that can be bought in a supermarket in Norfolk […} as commonplace in their way as tomato ketchup. Even the sweet-smelling ginger plant that looks so at home by the pathside is an aggressive coloniser. This place is not so much Paradise Lost as Paradise Replaced – a paradise of aliens dressed up to look as if they belong. The massive assurance of the trees is play acting. ‘
Hawaii has only one two-thousandth of the area of the United States as a whole, but it accounts for 70% of all recorded extinctions in the US and for 75% of all animals listed as endangered in the USA. 40% of 70 of Hawaii’s endemic bird species are extinct. The Hawaiian Rail (above) was flightless, and was probably exterminated by the black rats which came with the first Polynesian settlers. Other birds were killed when mongooses, brought in to deal with the rats in the sugar plantations, turned out to be ineffective against the rodents because they were diurnal, and the rats only emerged at night. Instead, the hungry mongooses turned to the nestlings and eggs of birds, with the result that only Kauai, which didn’t introduce the mongooses, still has a ground-nesting bird population.
And so habitat destruction and introduced species have played, and continue to play, havoc with island species around the world. Conservation organisations fight an uphill battle with invasive plants, entrenched interests and the need to balance the economic needs of what are often very poor countries with the need to preserve unique ecosystems. Every island group has extraordinary individuals who are working to preserve what’s left of their habitats, and they give me a lot of hope. It does seem sometimes as if the extraordinary short-termism of human beings could cause the end of everything, but I prefer to remember the determination and guts of people that I’ve met who are dedicated to make sure that something survives and thrives. It’s too late for the Hawaiian honeycreepers, but it might not be too late for the Kakapo.
The Kakapo is the only flightless parrot in the world, and was saved from extinction by a combination of moving it to a predator-free island, supplementary feeding and intense monitoring. Even today there are only a couple of hundred individuals, but the population is growing slowly. However, in its heyday the kakapo was found throughout New Zealand, and seems to have retreated to forest habitats because of introduced predators. It is a remarkable bird, the only parrot where the males get together and display to the females on a ‘lek’. Without the eradication of predators, however, I foresee it living out its years on the islands to which it has been introduced, under the watchful eye of humans.
And for those of you who have never seen Sirocco ‘in action’ with BBC presenters Mark Carwardine and Stephen Fry, you might want to have a look at the clip below, which is absolute television gold…
Photo One by KenVanVleck / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)
Photo Two by David Dennis / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0)
Photo Three By John Game, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=55571151
Photo Four By Department of Conservation – https://www.flickr.com/photos/docnz/4015891720/, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=48081940