INVASIVE SPECIES

Bangkok, 25 October 2015

A few weeks ago now, my wife and I were greeted with this site when we came out for breakfast on our balcony overlooking the Chao Phraya River

Huge mats – small islands, almost – of water hyacinth were floating by, on their way to the Gulf of Thailand. So big were they that they were interfering with the water buses as they zig-zagged across the river from pier to pier. They had to slowly push their way through the mats, rather like ice-breakers, to reach the piers and let off their passengers. As the days went by the mats got smaller, and now there are only clumps moving to and fro with the tide, some with a white egret perched on them going along for the ride. A flotilla of yellow boats went by yesterday morning loaded up with baskets full of water hyacinth.

They must be part of some collection system. Given the amount of the stuff floating in the river, it seems a doomed effort, more a way for the government to give jobs to the boys than to really clear up the river’s water hyacinth problem.

When we first arrived here a year ago, these mats of water hyacinth floating by were one of the things which had struck us about the river. Then, over the months, they had disappeared. We had almost forgotten about them when those huge mats greeted us at breakfast that morning of a few weeks ago. I suppose the seasonal rains had filled canals and reservoirs upstream enough for someone to open dykes and dams to relieve the pressure and in the process clear out the water hyacinths which had been quietly growing there all year.

Water hyacinth has a beautiful flower

which is why someone (or someones) took it out of its original habitat, the Amazon basin, and carried it off to botanical and private gardens around the world. But from there, the plant somehow made it out into the big wide world and happily colonized waterways which had never known it and had no biological weapons to combat it. It grows very rapidly and soon was choking up waterways, beautifully of course, but still choking the life out of them.

Water hyacinth is considered an invasive species, that is to say, a species which is not native to a specific location and which has a tendency to spread in that new location to such a degree that it causes damage to the environment, to human health, and/or to the economy. That certainly describes the water hyacinth. It invaded the waterways of Louisiana and Florida in the late 19^th Century, choking them up. In Africa, it’s invaded many places. It’s invaded the Nile, all the way from Sudan to Egypt. It invaded Lake Victoria in the 1980s (it was brought to Rwanda by Belgian colonists, who wished to beautify their properties, and then escaped into River Kagera, which led it to the lake). This is Kisumu harbour on the lake.

In India, it has invaded the Kerala backwaters.

In South-East Asia, apart from the Chao Phraya River and many, many other places, it has invaded Tonlé Sap Lake in Cambodia, a lake with a very unique ecology.

If you don’t control it, water hyacinth will cover lakes and ponds entirely, as these pictures show. This dramatically impacts water flow, it blocks sunlight from reaching native aquatic plants, and it starves the water of oxygen, often killing aquatic species. The mats are also create great places for mosquitos to live, as well as a species of snail known to host a parasitic flatworm which causes schistosomiasis.

I am reminded of a beautiful but evil woman: shall we say Julia Roberts as Snow Queen?

OK, to be gender-neutral let me also suggest a handsome but evil man: shall we say Robert Pattinson as Edward Cullen in Twilight?

To be fair to water hyacinth, it is not the only invasive species by any manner of means. There must be hundreds if not thousands of species which are considered invasive in some corner of the globe. The International Union for the Conservation of Nature (IUCN) has come up with a list of the 100 worst invasive species, confessing that it had great difficulty in squeezing the list down to a mere hundred (although water hyacinth did make it onto the list). Reading the list is eye-opening and depressing. Let me make a relatively random selection of a few of them. Kudzu, which has been receiving a lot of bad press as an invasive species, is on the list, and if this picture of a house smothered by kudzu is anything to go by, with good reason.

Originally from China, it was introduced to Japan, and from there to the US as an ornamental. Then during the 1930s farmers were paid to plant kudzu to combat soil erosion. Then it went crazy.

The brown tree snake, which has also received a lot of bad press as an invasive, is on the list too.

Originally from northern Australia, New Guinea, and some of the nearby islands, it was accidentally introduced into the island of Guam in the late forties-early fifties, maybe by crawling into the landing gear of an aeroplane, maybe as a stowaway on a ship. Once on the island, it went crazy, decimating, and in some cases completely eliminating, certain species of birds and rodents. Since Guam is a big transport node, it’s highly possible that the snake will get carried to other islands in the Pacific.

The fungus Batrachochytrium dendrobatidis, or Bd as it is known, is also there.

This little bugger has been wiping out frog populations all over the world, down to extinction in some cases. Only discovered in 1998, it’s thought that Bd originated in Africa and subsequently spread to other parts of the world by trade in the African clawed frog. Another fungus on the list is Ophiostoma ulmi sensu lato, better known as the fungus that causes Dutch Elm Disease. Originally from Asia, it somehow got into Europe in the early 1900s, probably in a shipment of Asian elm, but it was a mild form and was contained. From the Netherlands, it got into the US in the 1920s, through New York, where it has slowly but surely been killing off the North American elms. A much more virulent strain came back into Europe from the US in the late 1960s, probably in some infected wood, and has been killing off European elms ever since. This view of Salisbury Cathedral, for instance, painted by John Constable in 1820, is no more; the magnificent elms to the left have all died.

Closer to home, did you know that the cat is an invasive species?

Well, it is in certain parts of the world like New Zealand or Australia, or even the US. European colonists brought them, they have gone feral – or they just hunt for the fun of it – and have decimated, if not obliterated, certain bird species, and continue to do so. It’s so bad that it has made in onto the list of the 100 worst.

Staying with the familiar, the goat – an aggressive “eating machine” – is on the list, as are the rabbit, the red deer, the fox, the starling, and the rainbow trout, all introduced into new habitats by European colonists to make the colonies more like home, and all causing damage to the new ecosystems they found themselves in .

Going small again, I pick a mollusk from the list, the cannibal snail.

I pick it because it teaches us an important lesson in the fight against invasive species. The snail is an invasive in Hawaii, where it was originally introduced to try to eliminate another invasive species, the giant African land snail. Our friend is a fast and voracious predator, hunting and eating other snails and slugs, which gives it its pretty nickname. So the hope was that it would go after the giant African land snail. But instead, it went after the indigenous O’ahu tree snail species. And it went after them so enthusiastically that many of the species were extinct within a year. This is the risk with introducing a new predator to prey on an invasive species. There are chances that the predator will find other, indigenous, prey more yummy or simply easier to hunt, and you now find yourself with two invasives on your hands rather than one. Stoats, also on the list, fall into this category. Introduced into New Zealand to control the invasive rabbits and hares, it went after the indigenous birds instead, so now New Zealanders are left with trying to get rid of the stoat as well as the rabbit and hare.

For another plant on the list, the prickly pear, I refer the reader to an earlier post which I wrote about it. I’ll finish with a small tree, the cedar tree.

I add it simply because my French grandmother had one in her garden, and I loved climbing it when I was small. It was OK for her to have it, it is native to Europe and Asia. But when this tree, with its lovely pink flowers and feathery leaves, was introduced into the Southwestern US it was a disaster.

I invite readers to look at the list. It is quite sobering. In fact, as I study it, it occurs to me that there is one horribly invasive species that is not on it: homo sapiens sapiens.

This species left its original home in Africa 70,000 years ago and slowly spread all over the world. In at least three places, Australia, North America, and much later New Zealand, its arrival seems to have triggered a massive die-off of the bigger indigenous fauna, probably because they didn’t have sufficient defences against its clever hunting habits. About two hundred and fifty years ago, the species started the so-called scientific and industrial revolutions, which have resulted in it now having unprecedented power over all other species. It has, for its amusement or to make money or to protect one of its enslaved species (its agricultural crops and its livestock) from predatory attack or simply by mistake, moved species around the world, creating all the ecological catastrophes I’ve touched on above. And because it is taking living space away from all other species, crowding them out much more effectively than the kudzu pictured above is, it has set off the greatest die-off of species that the planet has seen in the last 66 million years.

I really think it should be on the list. I must write to the IUCN suggesting it.

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Water hyacinth on the Chao Phraya River: my photos
Water hyacinth flower: https://upload.wikimedia.org/wikipedia/commons/5/56/Common_Water_hyacinth.jpg (in https://en.wikipedia.org/wiki/Eichhornia)
Water hyacinth in flower in canal: http://img.tamtay.vn/files/2008/02/25/dinhkhoa/photos/247869/48c4920a_a019_resize.jpg (in http://blog.tamtay.vn/entry/view/472876/Thang-Sau-Co-loai-ve-dai-dot-trot-vuong-vao-yeu.html)
Kisumu harbor, Lake Victoria: https://en.wikipedia.org/wiki/Eichhornia_crassipes#/media/File:Kenya_Kisumu_Harbour_Hyacinths_1997ke09b21.jpg (in https://en.wikipedia.org/wiki/Eichhornia_crassipes)
Kerala backwaters: https://en.wikipedia.org/wiki/Kerala_backwaters#/media/File:Kerala-Backwaters_Alppuzha.JPG (in https://en.wikipedia.org/wiki/Kerala_backwaters)
Tonlé Sap: http://lh3.ggpht.com/-KcgJUhcsvQU/UE2G1p3L3GI/AAAAAAAAJl8/0bHMUxxUTAg/IMG_3439_thumb2.jpg?imgmax=800 (in http://jemamum.blogspot.com/2012/09/chong-kneas-floating-village-lake-tonle.html)
Julia Roberts snow queen: http://i.dailymail.co.uk/i/pix/2011/10/07/article-2046339-0E455A1E00000578-532_634x832.jpg (in daily mail; exact site is blocked by the Thai Ministry of Information)
Edward Cullen in Twilight: http://celebspics.org/wp-content/uploads/2012/11/05-Twilight%E2%80%99s-Breaking-Dawn-Part-2-The-Complete-Character-Gallery.jpg (in http://celebspics.org/twilights-breaking-dawn-part-2-the-complete-character-gallery/)
Kudzu: http://41.media.tumblr.com/d6bc26739854ba64e2b54c06a1993889/tumblr_ns2cl4QrQZ1r8vrhxo1_500.png (in http://sleepy-times.tumblr.com/)
Brown tree snake: http://islandarks.com.au/files/2013/03/Brown-Tree-Snake-.jpg (in http://islandarks.com.au/tag/brown-tree-snake/)
Batrachochytrium dendrobatidis: http://www.diark.org/img/species_pict/large/Batrachochytrium_dendrobatidis_JAM81/ (in http://www.diark.org/diark/species_list/Batrachochytrium_dendrobatidis_JAM81)
John Constable Salisbury Cathedral: https://en.m.wikipedia.org/wiki/Dutch_elm_disease#/media/File%3ASalisburyCathedral.jpg (in https://en.m.wikipedia.org/wiki/Dutch_elm_disease#Disease_range)
Cat: http://i1251.photobucket.com/albums/hh554/lemabang2008/Desktop%20Wallpaper/Cats%20Wallpaper%202/wildcat.jpg (in https://lemabang.wordpress.com/2012/08/19/desktop-wallpapers-2/)
Cannibal snail: https://en.m.wikipedia.org/wiki/Euglandina_rosea#/media/File%3AEuglandina_rosea.jpg (in https://en.m.wikipedia.org/wiki/Euglandina_rosea)
Cedar tree: https://en.m.wikipedia.org/wiki/Tamarix_ramosissima#/media/File%3ATamarix_ramosissima_a2.jpg (in https://en.m.wikipedia.org/wiki/Tamarix_ramosissima)
Human family: http://thumbs.dreamstime.com/z/family-sitting-garden-together-15588689.jpg (in http://www.dreamstime.com/royalty-free-stock-images-family-sitting-garden-together-image15588689)