Thank you!!

Well I'm really sad to say it but, it's time for me to say goodbye to you all and write my final blog entry.

I admit that when I first started writing, I was very nervous about the reception it would get and what direction my blog would go. But after a few posts, I felt more at ease and trust that you found it easy, straightforward and exciting to read. Writing it has definitely taught me a huge amount, not just about alien species but also about my own opinions on climate change and extinction. Before, I had never even thought about the possibility of  human's becoming extinct in the future!

Anyway, enough about me, I hope that from this blog I have taught you a few new facts about invasive alien species, including their effects on global biodiversity, how natural and anthropogenic forces are affecting their spread, how the extinction rates will be effected in the future, that not all alien species are negative and most importantly, that wallaby's reside in the UK.

I have tried to cover a wide range of topics and issues affecting non-native invasive species, as well as their economic and political effects on humans.

Hopefully by writing this blog I have succeeded at my main aim and inspired a few of you to look further into some of the topics surrounding alien species. Perhaps, maybe even motivated you to download or even use the PlantTracker App? (or is that a bit too far fetched?)

Thank you all for having followed my blog, it's been a great pleasure writing for you! I shall definitely be back soon!

I will leave you with this...

Aliens Banned

Yesterday, for the forest time in English history, the UK government decided to ban the sale of five non-native invasive aquatic plants (better late than never I suppose?)

Parrot's feather
(Myriophyllum aquaticum)

The plants which have been banned are:

• water fern
• parrot's feather
• floating pennywort
• water primrose
• Australian swamp stonecrop

(The plants highlighted in blue are all species found on the PlantTracker App)



The ban is due to come into force in April 2014.

DEFRA have said that the plants listed in the ban were chosen as they were overwhelming native species and were causing significant environmental and economic harm. As these plants had no natural controls in the wild, they were able to grow rapidly and form dense mats on the surface of rivers and lakes. Leading to the decline of other aquatic species in these waterways as the amount of dissolved oxygen is lowered. These mats also increased the risk of flooding (NNSS). 

I believe this is a step in the right direction to tackle the UK's invasive species problem.

However is it too little, too late? We shall have to wait and see!

Zebra Mussel Continued...

I have posted a short 2 minute video showing the effects of zebra mussels in the Great Lakes.

Give it quick watch and enjoy the music!!

Alien Species of the Week-Zebra Mussel (Economic Impacts)

Zebra Mussel (Dreissena polymorpha)

One invasive species which really caught my eye due to the rapidity of its spread and its potentially catastrophic impact on the freshwater ecosystems of North America, is the much maligned Zebra Mussel (Dreissenapolymorpha).

Zebra Mussels
(Dreissena polymorpha)

This small mollusc, averaging at around 2cm in length, is named as such because of the striped brown and yellow pattern on its shell. Native to Western Russia and the Black Sea area, they were transported to the Great Lakes region of North America via ships during the mid 1980s, with the first colonies being discovered in 1988 (Griffiths et al. 2011).

In this new environment relatively free of natural predators, its females capable of producing 100,000- 500,000 eggs per year, its population has exploded. With its ability to attach itself to hard objects (any object dropped in the water) and the long survivability of its larvae in water, it has since been able to rapidly spread to the Mississippi, its tributaries and surrounding lakes (Ricciardi et al. 2002).

Map showing the spread of the zebra mussel across the United States

The ecological impact of the mussel has been severe!! While their voracious filter feeding and breeding has greatly improved water clarity in lakes and rivers, they have also depleted the availability of microscopic organisms that play a critical part of the lake and river ecosystems. Indeed, fish numbers and biodiversity has decreased as juvenile and larval fish are starved of their main food (Maclsaac et al. 1992). Moreover, the Zebra mussels can also attach themselves to native mussels, killing them, which has resulted in the sharp decrease in native mussel numbers.

Their economic impact has been no less severe. Fisherman consistently have their lines destroyed by underwater Zebras, the future of commercial fish breeding in the Great Lakes region is at risk. They have also caused major problems for power and water treatment plants located by the lake shores – frequently clogging their water cooling intakes (Griffiths et al. 2011). 

The severity of the Zebra mussel threat to local ecosystem and their economic impact have been recognised by the Canadian and US government, as well as local government, which continue to devise plans to slow its spread.

Nevertheless, relentless conquest of North America seems unstoppable!!

King Crab and the Palmer Deep

King Crab (Neolithodes yaldwyni)

While scouring the internet in search of some interesting invasive species to showcase, I came across an article published in the biological research journal ‘Proceedings B’ (The Royal Society)  regarding the recent discovery of a species of deep-sea King Crab (Neolithodes yaldwyni) in Palmer Deep, a basin cut into the Antarctic continental shelf.  

King Crab
(Neolithodes yaldwyni)

The population of crabs are estimated to be up to 1.5 million, at a population density of 10 600 km², living at the depth of 850m. What is remarkable about this discovery is that these Lithodid crabs are thought to have been excluded from the arctic continental shelf waters for more than 14 million years due to their intolerance of water colder than 1.4C.  The crabs are thought to have crossed the Antarctic shelf to reach Palmer Deep.

With the warming of the oceans, it had been hypothesised that the fragile Antarctic ecosystem was at risk from future lithodid invasion. Nevertheless, this discovery has come as a surprise and indicated that the waters of the west Antarctic Peninsula are warming faster than previously thought. Indeed, the warming of the Antarctic waters has allowed these predators to establish themselves in this challenging environment (National Geographic).

While currently confined to dwelling at a depth of 850m, it is estimated that the peninsula shelf waters are warming at approximately 0.01°C yr⁻¹. The project leader of the team which discovered the crab colony, Professor Craig Smith of the University of Hawaii, told the BBC that that the species could spread up onto the shelf itself, to shallower depths, within the next decade or two.

Should the crabs spread to shallower waters, their impact on the ecosystem would be devastating. Not only do many of the native species – from brittle stars, urchins to sea lilies – not have resistance to the predatory crabs after 14 million years of isolation, but the crab has been termed an “ecosystem engineer” digging deep into soft sediments, preying on seafloor animals and altering basic habitat structure at the ocean bottom. Immediately above the 850m crab dwelling zone, the researchers found very few of the creatures they would have expected to have been in abundance at 50-100m depth. 

Perhaps this is a only a taste of what is to come?

Benefits of Invasive Species

There is a general belief that invasive species are inherently harmful to natural ecosystems. Up until now, most of my blog posts have solely focused upon the negative effects of invasive species. So instead I am going to change my attitude and look on the bright side of alien species.

For where there is a negative, surely there is always a positive? 

In certain cases, alien species are actually quite beneficial and can be both economically and ecologically advantageous. Many invasive species serve important but under appreciated roles such as providing desirable ecosystem services, replenishing human-damaged regions, serving as functional substitutes for extinct taxa and providing habitat or food resources to rare species (Schlaepfer et al. 2011). 

Catbird in a Honeysuckle

Scientists from Penn State University looked at the role of mutalism in determining the success of an invasive species. Gleditsch and Carlo (2010) discovered that since the introduction of the non-native honeysuckle plant to Central Pennsylvania, the number of fruit-eating birds e.g. robins, catbirds in the area has grown four folds. The honeysuckle and bird communities have formed a mutualistic relationship. 

The honeysuckle comprises more than half of all the fruits available in the landscape so acts as a main source of food to the birds.  In return, the birds benefit honeysuckle by dispersing the plant's seeds across a wider geographical area, mainly in territories already affected by human activities.

Thus, if honeysuckle were to now be removed from this ecosystem, it would almost certainly harm many native bird species whom rely on honeysuckle as their major food source. 

 In the Hawaiian rainforest, non-native species of birds are now the primary dispersers of seeds and fruits of some native plant species as a result of native birds having become extinct (Foster & Robinson 2007).

Furthermore, non-native species can also act as a catalyst for ecosystem restoration. For example, in Puerto Rico, former pastures with sparse vegetation and eroded soils are not readily recolonized by native trees. By contrast, non-native plantation trees are able to survive and so attract seed dispersers (Parrotta 1999). Sometime, non-native species are deliberately introduced to fill an ecological niche formerly occupied by a closely related species like on the islands of Mauritius. The Aldabra giant tortoises (Aldabrachelys gigantea) was introduced onto a few small islands, where they have successfully replaced the seed-dispersal functions of extinct native tortoises (Griffiths et al. 2010). 

Aldabra Giant Tortoise
(Aldabrachelys gigantea)

I have only scratched the surface of the numerous benefits invasive alien species can provide. Among the articles and papers I have read it appears that a bias persists against non-native species amongst the scientific community. Non-native species can cause the loss of biological diversity but as discussed they can provide wide ranging conservation benefits. 

In the future, invasive species could fill niches in degraded ecosystems and help restore native biodiversity in an inexpensive and self-organized way that requires little or no human intervention (Gleditsch and Carlo 2010).

Alien Species of the Week-Chinese Mitten Crab

Chinese Mitten Crab (Eriochier sinensis) 

The Chinese Mitten Crab originates from the Yellow Sea region, along the border with China and Korea. It was first recorded in Europe in the early XX century and is now common in Europe as well as in North America (Dittel and Epifanio 2009). Eriochier sinensis first appeared in the UK in 1935 (Thames river) but became firmly established in 1975 (Veilleux and de Lafontaine 2007).

Chinese Mitten Crab (Eriochier sinensis)

Its omnivorous nature makes the Chinese Mitten Crab a threat to local ecosystems due to its consumption of native species such as fish larvae, algae, detritus and a variety of macro invertebrates and aquatic plants.

As a result of its burrowing activity, the Eriochier sinensis is also a cause of river bank erosion and collapse. The economic impact of this alien specie in Germany, since its appearance in 1912, is estimated at around 80 billion euros (Global Invasive Species Database).

Cohen and Carlton (1997) (cited in Veilleux & de Lafontaine, 2007) identified 10 pathways that would account for the worldwide spread of the Chinese Mitten Crab:

• ƒ dispersal of larvae by currents 

• ƒ passive dispersal of adults or juveniles on floating material 

• ƒ transport of adults or juveniles by ship fouling 

• ƒ transport of adults or juveniles in cargo 

• ƒ transport of adults or juveniles on  semi-submersible drilling platforms, 

• barges and other long-distance slow-moving vessels 

• ƒ transport of larvae or juveniles in ballast water 

• ƒ transport of adults or juveniles in fisheries products 

• ƒ transport of larvae in water with shipments of live fish 

• ƒ escape or release from research, public, or private aquaria 

• ƒ intentional transfer to develop a food resource

General distribution of mitten crab Eriocheir sinensis populations in their native and invasive ranges.Circles correspond to established () and non established populations () in non-native range; () indicates distribution in the native range.

(from Dittel & Epifanio, 2009)

So far the eradication measures such as the physical trapping of the crabs has not proven successful.

Check out this video:

Philine zu Ermgassen, Freshwater Ecologist at the University of Cambridge, talks about its identification, impacts and management in Great Britain:

Further reading on the spread of Eriochier sinensis:

NOBANIS –Invasive Alien Species Fact Sheet

DAISIE - Species fact sheet

Natural History Museum - Chinese Mitten Crab page