Monday, January 2, 2012

Forest Destruction and Invasive Plants on Chiloe


The island of Chiloe holds some of the region's last, and greatest, temperate rainforests (bosques templado-lluviosos). However, little of their former range still exists as forest, much to the detriment of the whole host of wonderful endemic creatures (from the 5mm long scorpions to the 3,600 year old Alerce trees) that inhabit them.

I have known about old-growth forest destruction for years, but being a New Englander, I had never witnessed it firsthand (we cut all our forests hundreds of years ago!) and it seemed an abstract concept - like parachuting or actually catching fish while fishing. But I got the point awhile back. One of the other researchers here, Ariel, who studies mammals here (but is getting a PhD in biogeochemistry) was preparing a talk for a conference on Monitos, which he had researched for several years. One of his projects looked at habitat use in different forests, so he needed to take some pictures of his old study sites, which he had not visited in two years.

Argopteron aureipennis, a skipper that only lives in clearings in forests with Quila bamboo,
where the males dance for mates - flashing their iridescent gold wings. 

After some difficulty finding the desired site, we walked in about 15-20 yards into the seemingly intact forest and saw the damage – all large trees in one area had been cut and they seemed to be clearing the understory and brush from much of the rest. One small section of old forest was left as was the section between the road and the cuts.

After surveying the damage we returned and talked to others at the center about it. Apparently it followed the typical logging routine here: cut forest away from the road, allowing the area near the road to stand. Of course, in a few years, that too will either die or be cut – a section of forest 200m x 20 m is not going to survive. And then the invasives will move in at the expense of the native plants.

Ariel surveys the once old-growth forest

One of the sharpest memories of my first few field days in Argentina was simply that I knew a good number of the plants. I am not a botanist but I have a pretty good knowledge of the common New England plants. And here they were: in Argentina. And then in Peru. And then in the Bahamas. Even Tierra del Fuego had some old friends: hawkweeds and dandelions popping out of the sidewalk, daisies in the fields – not to mention the muskrats, beavers, trout and salmon that have completely demolished almost all of the wetland ecosystems in the area.

Here in Chile though, it seems worse. On Chiloe, acres upon acres of Scotch broom turn the countryside yellow, a common forest type is Eucalyptus, you can get as mired in patches of blackberry  as at home and a maple species (I think it is Norway) is taking over roadsides. In Santiago it was hardly better: tree-of-heaven (Alanthius) sprouting in any barren place with the standard set of weedy exotics around it.

Eucalyptus grove, Argentina

South America has had a short history of interchange of flora with North America/Europe/Asia, geologically speaking, of course. Instead, much of the flora (and fauna) is similar to that of Australia and Africa, as they were once connected in the supercontinent of Gondwana after the breakup of Pangea. Nothofagus, the dominant tree genus in Tierra del Fuego, and common here on Chiloe shows this Gondwanan distribution well, it occurs in South America, Australia and New Zealand. The common ferns here, in the genus Blechnum, are also found in New Zealand. Marsupials radiated in Australia and South America – now in both they are threatened by human activity – development of the fragile habitats they inhabit and our introductions: dogs, cats, rats, plants and more. Were it not for these introductions, the logged areas of Chiloe would grow back into the standard Chiloe forest (eventually), instead, it turns into a monoculture of Eucalyptus or a scrub of Scotch broom.

However, let's not carry this pessimism too far. I am firmly of the belief that over time, many invasives get assimilated into the community. Of course, we do not know the consequences at the time of older invasions, in New England, for example: plantain, dandelion, daisy, and many others, including some that we probably just associate with our region. Will autumn olive, purple loosestrife, Japanese beetles and gypsy moths integrate into the communities which they invade or remain hugely damaging species forever?

This dung beetle - I think Homocopris torulosus - has increased substantially with development and introductions
of cattle/sheep/horses and the massive increase in dung that comes with them. 

Some evidence points to the former. The famous story is the Brown-tailed Moth, which is probably better known for its horrible sting than anything else (the caterpillar sends people to the hospital with regularity!). But it was a huge problem species in New England during the first half of the 20th century – its range extended into every state and was a pest of many tree/shrub species. Then, rather suddenly, it declined – and now is found on a few islands in Maine and at the very tip of Cape Cod. Why? One paper claims that an introduced parasitic fly probably played a big role and the authors did a very clever experiment to support this by transferring caterpillars to plots within the former range, which resulted in higher mortality than found in the remnant range. Other invasives have expanded and then contracted as well: the Skylark and Mynha in the Pacific northwest, hops in the northeast, Argentine ants in several places. And others, such as English plantain, have become hosts for native species (in that case, the Baltimore Checkerspot).

Here in Chiloe, I found one native butterfly, Butleria elwesi, ovipositing on a European grass, suggesting that here – where the history with such species is shorter than in New England (Darwin remarked on the lack of cleared land when he passed through Chiloe) – adaptation to these exotic species is occurring, too. In 200 more years, will Eucalyptus trees peek through the canopies of Nothofagus forests? 

B. elwesi, showing the distinctive underwing pattern.
Egg of B. elwesi, on I think, Dactylis sp


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