Aliens Among Us!
The giant snakehead (Channa micropeltes) is a recently introduced species to the southern United States which is causing problems in many of the local ecosystems, not to mention fear amongst the residential members of many communities (source: amazingdata.com).
When the majority of people hear the word alien they automatically think of things such as extraterrestrial beings, UFO’s or abductions. However, in all reality, we don’t have to look far to find aliens among us. I am talking, of course, from a biological perspective and the aliens referred to here are not the big-eyed, scrawny green figures depicted in countless books and movies – I am indeed referring to invasive species.
“Aquatic invasive species are destroying the environment, damaging fisheries, and costing American taxpayers billions of dollars annually.
- John M. McHugh“
For the purposes of this article, invasive species, also referred to as non-indigenous or non-native species, will be defined as species that are not native to a region and can adversely affect species which are native (naturally occurring) to that particular area – they have negative impacts on an ecological and economic scale and can sometimes negatively affect human health. Invasive species can be plants or animals, both terrestrial or marine (or aquatic in the case of freshwater) and can wreak havoc on ecosystems by out-competing other organisms for valuable resources such as space and food. Many invasive species are considered top predators in food webs and can simply wipe out entire populations of native species through predation. Moreover, numerous invasive species have been shown to spread rapidly and take over a wide geographic range relatively quickly, eliminating vast amounts of native species.
Zebra mussels (Dreissena polymorpha) attached to a treeridge clam (Amblema plicata). These mussels will attach to any hard substrate and often this results in attaching to other benthic molluscs leading to their subsequent mortality. They can also outcompete native clam species for space (source: forestryimages.org).
One family of such invasive organisms which has been identified in North America and is quickly spreading through the southern United States is a group of predatory fish known as the snakeheads (Family Channidae) [Courtenay & Williams, 2004]. These non-native fish were introduced to control fish populations in the southern areas of United States. They are extremely aggressive and include species such as the giant snakehead (Channa micropeltes) and the bullseye snakehead (Channa marulius). Many of these fish are able to crawl on land and breathe air, allowing them to spread quickly across land. Additionally, these fish can become quite large, and being on land has resulted in fear amongst humans that small pets and children may be in danger. As top carnivores, snakeheads can also have a drastic effect on the ecosystems they invade by wiping out entire populations of native fish species, and hence altering the entire ecosystem and having harsh effects on local fishing industries (Courtenay & Williams, 2004).
Intentional introduction of species is not the only way in which species can spread from one geographic location to the other. Many foreign species which have been established in North America for centuries were accidentally introduced to Europe as far back as the 1800s. One typical mode of accidental introduction of species is ballast water. Many species of fish and benthic invertebrates were introduced to North America centuries ago via the ballast water of ships – some which have become common, household names in North America (for example the soft-shell clam, Mya arenaria). Moreover, many species of mussels which were introduced to North America via ballast water from European ships have taken over and dominated various benthic marine habitats here in North America. Such species include the zebra mussel (Dreissena polymorpha) and the mediterranean mussel (Mytilus galloprovincialis).
Purple loosestrife (Lythrum salicaria) dominates this open field. This invasive species will out-compete all other vascular plants in optimal conditions leading to the suppression of native plant species (source: gettinginthegroove.com).
Conversely to invasive marine organisms, plants can do just as much damage to the ecosystems in which they establish themselves. For example, purple loosestrife (Lythrum salicaria) was introduced to North America in the early 1800’s as an ornamental plant and had spread to the northeastern United States by 1880. This vascular plant is known to disperse very quickly and is extremely common in North America. It can spread over vast areas and will out-compete many native vascular plants, causing their suppression and subsequently dominating the habitat (Stapelton et al., 1998). Other invasive organisms include various types of algae, bacteria and other microscopic organisms, worms, fungi, snakes, insects, molluscs and other marine invertebrates and many others.
These invasive species are taking over entire habitats, destroying populations of economically valuable species, and some even pose threats to human health – so what can we do to prevent the spread of these home-grown aliens? It’s pretty straightforward and simple really. First you have to become aware of which species are native to your area and are naturally occur there. Next, educate yourself of species that are feared to become invasive and a threat to habitats in your area. Your local and federal government will often provide a list of species that are considered to be potential threats specifically to your geographic area. Once you’ve educated yourself, simply keep your eyes open! If you see a strange, uncommon species of any kind that you think may be invasive or alien, call your local environmental authorities and inform them of where, when and what you saw – the earlier the invasive species is discovered, the better the chance of it being eliminated, not dispersing and not having drastic negative effects on immediate ecosystems.
If you would like to learn more about invasive species, particularly in Eastern Canada, visit http://www.projectufo.ca/drupal/. This is a website created by Cape Breton University to educate the public of invasive species in Cape Breton, Nova Scotia, Canada.
The video below also provides a good, general outline of what invasive species are and various different types (with the help of some classic tunes…).
See Series: CONSERVATION CONVERSATION
References:
Courtenay, W.R. and Williams, J.D. (2004). Snakeheads (Pisces, Channidae): a biological synopsis and risk assessment. USGS: Denver.
Stapleton, C.A., McCorquodale, D.B., Sneddon, C., Williams, M. and Bridgland, J. (1998). The distribution and potential for invasiveness of some non-native vascular plants in northern Cape Breton. Parks Canada: Atlantic Region.
[...] out there, something truly intelligent – the Demiurge – the architect – the alien and advanced entities that must inhabit some mysterious parts of the [...]
[...] People may feel that they have spoken or been spoken to by a higher being, been in contact with aliens or a bevy of other wholly “other” happenings far outside of the normal realm of day to [...]
[...] deep that can, in real-time, be viewed by scientists, but also to “fine-tune the search for extraterrestrial life” says Kevin Hand, astro-biologist at NASA (source: National [...]