An example of IAS on an island

In our modern age of extinctions, islands qualify as biodiversity hotspots. They combine the high levels of unique biodiversity, recent species extinctions and of likely future species losses (Whittaker and Fernandez-Palacios, 2007). This therefore means that protection of these hotspots is required, as well as monitoring and observing species and species interactions to prevent extinction taking place, in effect acting to conserve local species. The following post provides examples of invasive alien species in Sri Lanka, how they have come to be present and potential methods to mitigate their impact as well as remove them from society and the area.

Sri Lanka has experienced over 500 years of colonial history, in which the accidental and facilitated introduction of invasive alien species (IAS) has grown through the horticultural and agricultural trade, slave trade and the colonisation of the island by European settlers. It is during this time that many of the invasions have taken place. Introductions during this time were entirely intentional (Marambe et al., 2001). Current trends however show that this observation has shifted from intentional introductions to unintentional. This perhaps reflects the change in IAS drivers over the past 50 years.  The intentional introductions were for agricultural and forestry purposes and they have now become a cornerstone for the country’s economy. Such introductions include tea plantations, rubber trees, coconuts as well as timber plants and therefore the benefits have been huge for Sri Lanka’ economy. Aside from these intentional introductions, many other species have invaded natural ecosystems or spread rapidly in human-modified ones where the consequences have spanned not only from ecological issues but economic and social issues.

Between 1997 and 2001, 34 species of alien biota were present on the island, these consisted of 13 animal species and 21 plant species, 12 are aquatic and 22 are terrestrial. The reasons behind this high level of IAS have been associated with the macroeconomic policies that have introduced in the 1970s, for example the liberalisation of the financial sector, allowing market freedom (Marambe et al., 2001). More recently, efforts to diversify the agricultural sector have resulted in private institutes and NGO’s attempting to import alien organisms for agricultural purposes. Such introductions include the introductions of molluscs to meet increasing consumer demands (which have yet to be identified) and the Golden Apple Snail, whose introduction in 1980 has been associated with the aquarium trade, originally from South America. The Golden Apple snail has become a huge pest within rice farming communities, decimating rice crops across the country.

Traditional practices have also enhanced the establishment of invasive alien species. Traditional forms of weaving have encouraged the growth and preservation of alien reeds and grasses that are invasive species of fallow marshy land and wetlands.

Intentional introduction has taken place on Sri Lanka via the horticultural industry, introducing plants to the Royal botanical Garden at Peradeniva. Such cases include the water hyacinth (Eichhornia crassipes), this plant was introduced in 1905 and enacted in 1907. Even after enactment, the hyacinth became a major aquatic weed, having both environmental and economic implications, through ‘choking’ of water bodies and damaging irrigation systems. The plant has since been mechanically removed which is a long, intensive and tedious process, however in the 1980s biological techniques were employed to manage populations, however its effectiveness was not as great as expected. There still, to this day remains no alternative technique to mechanical removal.

Deliberate introductions have also taken place by other means. Plants such as the Salvinia (Salvinia molesta), were introduced in the 1930s for scientific interests, to purify water, but has now become a major aquatic weed. There is no current information on the levels of infestation but in 1988, 8000 ha of rice fields. An eradication scheme was initiated in 1957 but was abandoned in 1964 due to a lack of funding and so the populations have been able to increase since, unchecked.

The few examples shown in the case of Sri Lanka above highlight the changes in how invasive species are introduced and how our interest in scientific investigations and agricultural advancements has manipulated the pathways along which invasive alien species have moved.  These introductions have led to the decline of more sensitive species and therefore more action is required. According to Marambe et al., (2001) there is a no policy-level initiative to control the spread of IAS, this is partly due to a lack of funding, however it is predominantly due to a lack of knowledge on the consequences of the presence of IAS in ecosystems. Sri Lanka therefore needs to improve current awareness and advance scientific knowledge and understanding in the field to prevent further extinctions taking place, contributing to the many already seen in contemporary times.

http://books.google.co.uk/books?hl=en&lr=&id=sE6jEHVvwYAC&oi=fnd&pg=PA135&dq=human+dimensions+of+invasive+alien+species+in+sri+lanka&ots=t8ZuDrHi_2&sig=JFgikT5tFRkYBipXyPomXCw4WKs#v=onepage&q=human%20dimensions%20of%20invasive%20alien%20species%20in%20sri%20lanka&f=false

Whittaker, R J and Fernandez-Palacios J M, 2007, Island Biogeography – Ecology, Evolution and Conservation, 2^nd Edition, Oxford

Characteristics

I thought it would be important to provide a brief snippet of information on the traits and characteristics of both threatened and endangered species as well as those of invasive alien species. The characteristics of those species that are threatened by invasive alien species have relatively similar characteristics. According to the Florida Forest Stewardship, these are:

1. species with narrow habitat requirements and therefore unable to adapt to change

2. species of economic importance

3. species of large size

4. species having limited numbers of offspring per breeding period, long gestation periods or requiring extensive and intensive parental care

5. species with highly specialised adaptations

Typically, characteristics of invasive, alien species, as defined by the Pacific Northwest Research Station:

1. ability to tolerate a wide range of habitat conditions, i.e. they are less specific and more generalised individuals

2. the ability to grow and reproduce rapidly

3. Effectively and aggressively compete for resources

4. Lack of natural predators/pests/threat to growth in the new ecosystem

The combination of the characteristics of both the threatened species and the invasive species are what lead to the extinction and loss of of species in particular areas. It is therefore necessary to educate and understand the fragility of certain ecosystems and their interactions to prevent the loss of species.



http://www.fs.fed.us/pnw/invasives/index.shtml
http://www.sfrc.ufl.edu/Extension/florida_forestry_information/planning_and_assistance/threatened_and_endangered_species.html

Biocontrol Gone Wrong

Myxomatosis is a disease caused by the myxoma virus. The virus occurs naturally in certain rabbit species found in South America and in California and when present, only causes mild symptoms. It was first discovered in Uruguay in 1896 when the symptoms were first observed. These symptoms include bulging eyes, localised swelling around the head, face, ears, lips, anus and genitalia. The severe swelling can lead to blindness and facial distortion, leading to difficulties in drinking and eating. Myxomatosis is also associated with fatal pneumonia due to respiratory infection. There is no specific treatment for the virus and any treatment given is purely supportive, therefore the recommended way to deal with rabbits infected with the disease is to euthanise them to stop them suffering. It is therefore important to control the spread of the virus.

Myxomatosis is transmitted, particularly in Britain, via insect vectors (Ross and Tittensor, 1986). Insects that puncture the skin allow the bacteria to infect the host and therefore display the symptoms. It is therefore important to manage fleas when found on rabbits and to treat them immediately if there is an outbreak of the disease at the time.

The disease was imported into Australia in 1951 to control large rabbit populations with devastating effect. The disease was then illegally introduced to an estate in France in 1952 and spread naturally throughout wild rabbit and domestic rabbit populations across Westen Europe. The first case was reported in Kent in 1953 and was found across all of Britain by the end of 1855. The impact of the disease in Britain was devastating, it eradicated 99% of rabbit populations in an extremely inhumane way (Ross and Tittensor, 1986). The whole event taking place due to the introduction of a non-native pathogen for biological control of undesired species, highlighting mankind's inability to effectively control introductions and how our lack of knowledge of species interactions can lead to dramatic effects.

Myxomatosis, however, has been present in pulses. After the initial introduction in 1953 in Britain, the number of reports declined. This can be explained through the concept of critical community size (CCS), discussed by Fouchet et al (2008). Fouchet et al (2008) explain that the CCS of a host population infected by any parasite defines a point where the two time scales of extinction are very different between populations above or below the CCS. If above the CCS, extinction rates are much greater as the pathogen can maintain itself almost indefinitely and individuals within the population are regularly exposed to infection. Extinction rates below the CCS is much less and the parasite/infection will rapidly die out after it has been introduced into the population. However, a limiting factor of any parasite/virus/bacteria is its efficiency. What is often the case if the agent is particularly efficient at decimating host populations is the extinction of the agent itself as it manages to kill the host before transmission to another host (Fouchet et al, 2008). The CCS has been shown to significantly alter relationships between the host and the agent. The transmission of the bubonic plague from rats to humans has been found to take place when the rat populations are below the CCS and the agent moves to find the next available host. This happens, as stated before, because the agent is so efficient at killing the host, once an outbreak is present in a populations, the population numbers crash pushing the agent to find the next suitable host. This transmission, thankfully for human populations, has not taken place with myxomatosis, however the concept can be applied.

Presently, all domestic rabbits are immunised against the virus and an transmissible vaccine has been implemented for wild rabbit populations (Torres et al, 2001). However, this is another form of biocontrol and could potentially have similar undesired effects to that of myxomatosis, however tests with this vaccine have shown no undesired side effects (Torres, et al, 2001).

The case of myxomatosis show that bio control can be implemented and controlled effectively, however in this instance the process is incredibly inhumane. However, if the correct control measures and precautions are not put in implemented, the agent becomes an unwanted invasive alien species with, especially in this case, detrimental effects.

http://www.sciencedirect.com/science/article/pii/S0022519307005413
http://www.sciencedirect.com/science/article/pii/S0264410X01001840
http://www.jstor.org.libproxy.ucl.ac.uk/stable/pdfplus/2404476.pdf?acceptTC=true
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.1986.tb00038.x/abstract

A video post

Aside from some fairly irrelevant video clips, this video discusses the human thought and outlook our impact on biodiversity present day biodiversity loss. It discusses how humans ourselves may become extinct due to our dependence on ecosystem services and therefore why we should act to preserve it. It does however provoke thoughts of the decoupling of nature and human society, it further demonstrates how we are to act as stewards to preserve the world around us and does not necessarily consider human kind as natural or a part of the wildlife. 

Another issue that I feel is brought across in this video, is the identification of scientists as the sole provider of information on the human effects on the biosphere. On a local scale, communities have seen the decline in biodiversity, in particular with respect to invasive species for centuries and have therefore decided to act upon it through community led management approaches. For example forestry management in Orissa, India (Nayak, 2008).

The video does however highlight the issue of conservation and preservation of all things wonderful that exist on the Earth and not just figure-head species such as 'bicen and pandas'. For me this is important with respect to invasive species and their influence on species extinction. The impact of invasive species is often at a low trophic level, with the effects cascading down the trophic levels, or frog-leaping them entirely and removing the niche that was once occupied by an endemic or native species prior to invasion. Such is the case particularly with respect to intentional agricultural invasions in order to increase output to meet consumer demand.

The video also highlights human higher brain function and the role of our 'enhanced' intelligence compared to the wildlife around us, and how this should be utilised to better the world around us, for it has enabled us to advance technologically within our society. This again demonstrates the decoupling of mankind from nature, and as true as it may be, I feel that the more we forget about our association with nature, invasions will continue to take place, with more unintentional introductions taking place and the loss of species globally.

However, watch it and see how thought provoking it is for yourself from an ecologist point of view and perhaps about how the anthropocene is different with respect to extinction events. 

Are invasive species really that bad?

After reading articles on how invasive species are bad, how they reduce biodiversity and cause extinction through out competing the less adapted and more specialised native species, I stumbled across 'An Essay on some Topics Concerning Invasive Species' (Brown and Sax, 2004). This article brought a new insight to how to think about invasive species for myself, it views the occurrence of invasions as 'unintentional, uncontrolled experiments' that could potentially provide insights into how human caused invasions shape and alter ecological and evolutionary processes, in some respect 'generating and maintaining biodiversity'.

The article seemed to tap into the complexities of thought behind the issue of invading species, associating it with our fear of the foreign, our xenophobic thoughts, and how these thoughts are manifested in our actions to prevent the invasion taking place or doing our utmost to remove it once the invasion has taken place. This though is backed by our own ideas of associating the original environment as pristine, where in fact the conditions may have been worse prior to the invasion, or by our own doing the invasion has been allowed to become established through our presence. The conditions worsened by our own selves, this judgement of prior conditions is based on a decoupling of nature from our society, where human beings take on a role of stewardship instead of embracing the fact that we too are as intrinsically involved in nature as any other aspect of this world.

Brown, J.H and Sax, D. F. (2004) 'An Essay on Some Topics Concerning Invasive Species' Austral Ecology, "9, 530-536 (http://onlinelibrary.wiley.com/doi/10.1111/j.1442-9993.2004.01340.x/pdf)

Crayfish

For those who are interested, the inspiration for the return of the crayfish discussion:

http://www.bbc.co.uk/news/uk-england-coventry-warwickshire-15447581

(I dont know how to upload a video from the web other than it being on youtube or from my own computer so if anyone knows how to, it would be great if you could help)

The Case of the Signal crayfish

Oh yes, for those who did ecological patterns and processes last year, the tall tale of the signal crayfish is back for this post after reading an article on the BBC website inspired a small investigation.

The American signal crayfish Pacifastacus lenisculus has been detrimental in the decline in native European crayfish species. With its introduction via commercial culture (Alderman et al 1990) it not only establishes itself as a more adaptable and therefore more prevalent species within freshwater ecosystems but its resistance to the crayfish plague has been the most dominant advantage it has over the European crayfish. Gren et al (2008) are one of many articles discussing the issue of the signal crayfish carrying this plague, caused by the oomycete, Aphanomyces astaci Schikora (Alderman et al 1984), which when introduced to a new area threatens native populations with extinction. Gren et al (2008) discuss this issue in relation to Sweden due to the association of crayfish with recreational and cultural traditions, such as a cuisine delicacy corresponding to 0.5kg/person/year, and the impacts that this has on the presence of non-native crayfish. Crayfish caught in Swedish lakes accounts for about 35% of the total consumption and the 65% left over is imported internationally. In Sweden alone, signal crayfish account for 85% of the total number of crayfish harvested, however harvesting is not the only way that the presence of crayfish is being appreciated; crayfish are being caught be recreational divers.

The signal crayfish was introduced into Swedish waters in the 1960's to compliment native crayfish populations as they were in severe decline, partly due to exploitation but also, due to the fungus plague. As stated by Gren et al (2008), the idea with the introduction was for the signal crayfish to replace the native crayfish and 'fill the ecological niche' that was left behind by the loss of the native species. The issue with this introduction in the 1960's was that the knowledge behind the transference of the plague, which had been present in Sweden since 1907(Unestam, 1969), was not entirely certain, and it was discovered that the signal crayfish was a carrier of the plague. With this revelation, signal and noble crayfish therefore could not co-exist in the same environment for this reason alone, let alone the physical dominance of the signal crayfish out competing the native noble and its increased mobility. This was confirmed by a study by  Fiskeriverket and Natuvardsverket in 1998. This led to the imposition of regulations on the introduction of signal crayfish, however they were still being introduced by those who were able to obtain permits. The article concludes, after analyzing the impacts of economic factors on the occurrence of signal crayfish, that restrictions need to be imposed as the spread of the species is not likely to decrease from economic development, its spread can be described as independent from economic factors, the primary introduction alone was enough.

The article by Gren et all (2008) is one of many examples of how species in contemporary times have been facilitated to meet the increasing demands of the human population. This shows how the signal crayfish was purposefully introduced to supply the local populations of Sweden with a favoured delicacy. As to my previous post, this deliberate introduction has had dramatic implications on the populations of the local noble crayfish of Sweden, as Gren et al (2008) states, populations in areas have been driven to near extinction.


Alderman, D. J, Polglase, J.L, Frayling, M, Hogger, J. (1984) 'Crayfish plague in Britain', Journal of Fish Diseases 7. 401-405.

Alderman, D. J, Holditch, D, Reeve, I. (1990) 'Signal crayfish as vectors in crayfish plague in Britain', Aquaculture, 86, 3-6

Gren, Ing-Marie, Campos, Monica, Edsman, Lennart, Bohman, Patrik (2008), 'Incomes, Attitudes, and Occurrences of Invasive Species: An Application to Signal Crayfish in Sweden', Environmental Management, 43:210-220

Unestam, T. (1969) 'Resistance to the crayfish plague in some American, Japanese and European crayfishes, Report of Istitute Freshwater Research, 49, 202-209