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

Are we nearing a 6th Mass Extinction?

Having already looked at the impacts of several alien species on their invaded environment, I think is important to examine past and future extinction rates.

So I thought we should delve into the past and examine whether or not we are entering into the Sixth Mass Extinction?

What are Mass Extinctions?

Mass extinctions are defined as the loss of  at least 75% of Earth's species in a geologically short time frame (Jablonski and Chaloner 1994). Palaeontologists recognize five major extinction events ("Big Five") in the past 540 million years, with the most recent mass extinction event ending 65 million years ago-Cretaceous (Barnosky et al. 2011).  The "Big Five" mass extinctions took place near the end of the Ordovician, Devonian, Permian, Triassic and Cretaceous Period . As the number of known species which have become extinct over the past thousand years has risen, biologists suggest that a sixth mass extinction may now be under way.  It is expected that if all species currently deemed "threatened" become extinct in the next century, then future extinction rates will be 10 times recent rates ( Pimm et al.1995)-astonishing!!

Mass Extinctions and CO2 Levels

What are the main causes?

Observations suggest that humans are the main cause of this sixth mass extinction, through habitat fragmentation/ modification, introduction of non-native species, spreading pathogens and killing species directly (Barnosky et al. 2011).  All of these human activities are associated with climate change through global warming due to increasing levels of carbon dioxide, increasing levels of volcanism and ocean acidification. According to the graph above,  all major extinctions occurred when CO2 levels exceeded a thousand parts per million (ppm). Highlighting the important role human's play in determining the speed at which we meet the sixth extinction. 

The graph below, produced by Barnosky et al. (2011), compares extinction rates versus extinction magnitude across different geological time periods. It shows that in the future, if current extinction rates over the last 500 years were to continue it would produce a "Big Five" style magnitude mass extinction. This means that current extinction rates for species are either faster or just as fast as all rates that would have produced the "Big Five" extinctions. 

However, I must point out that you should take CAUTION when comparing extinction rates, as the fossils used and quality of their preservation varies greatly. For example, many of the earlier mass extinctions rates were solely based on marine organisms.

Extinction rates versus extinction magnitude

Today, the current rate of species extinctions has most definitely been enhanced by human activities as CO2 concentration levels increase. Although, recent species loss is definitely serious and dramatic, we can't yet call it a mass extinction. However, the number of species now classed as "critically endangered" suggests that a sixth mass extinction is soon to become a reality.

This makes me question as to what the future holds for us humans and when will we potentially become "extinct"?!?

Power of the App!

 

So far I’ve spoken about some of the difficulties caused by invasive/alien species, but how as a member of the public can we help combat these invasions? 

Well the answer is simply “PlantTracker!"

The Environment Agency, the University of Bristol and the Centre for Ecology and Hydrology have teamed up and developed a FREE app allowing the public to identify some of the UK’s most problematic invasive, non-native plant species. 

The PlantTracker app allows users to very easily identify 14 invasive plant species (e.g. Rhododendron) with the help of an image gallery and a detailed description of each plant species. What is also great about this app is that it also includes a “Confusion Species” gallery, making it easier to distinguish non-native from similar looking indigenous plants. Furthermore, once you have identified one of the invasive plant species using the app, you can submit a geo-located photo of the specimen.

PlantTracker screenshot options

 

Why an app?

It is crucial to gather solid data to make important decisions on how to manage and deal with the problem of invasive plant species. However, it is usually very difficult collect verifiable and accurate data about the distribution of these invasive plant species. But by combining the smartphone application with the power of crowd-sourcing data collection, the app allows real time and verifiable data to be collected (see below).

Map showing the distribution of Rhododendron reports.
(The red dots indicates the number of verified Rhododendron records)

Where can I get the app?

PlantTracker is available free from the iTunes App Store and Android Market. So go on, why not give it a go and download the app? I’ve already downloaded mine!

Alien Species of the Week: Nomad Jellyfish

Rhopilema Nomadica (Nomad jellyfish)

Originally from the Indo-Pacific, the Nomad jellyfish first made its appearance in the Mediterranean in the 70s via the Suez Canal, while the first mass appearance was registered in 1995 in Mersin Bay, off the coast of Turkey (Öztürk and İşinibilir 2010). 

The large presence of this invasive species in the Mediterranean is a cause of concern for the local populations (due to the particularly bad stings), and also for the tourist industry in the affected areas, such as the Israeli coast. The Rhopilema Nomadica affects fishing as well, as it gets entangled in fishing nets and  also eats fish larvae, causing a decrease in the fish stock (Galil 2007).

Nomad Jellyfish (Rhopilema Nomadica)

Due to its rapid spread, the Rhopilema Nomadica is included in the list of the 100 worst invasive species in Europe within the Delivering Alien Invasive Species Inventories for Europe (DAISIE). Its diffusion is diminishing plankton resources and is being detrimental to fishing, tourism and coastal installations. Seasonal variations in water temperature regimes could help fight the annual occurrence of the nomadic jellyfish, whose presence has been further recorder in 2004 in Malta and the Sicily Channel ( Deidun et al. 2011). 

The discovery of R. Nomadica in Maltese waters is another alarming indication of the increasing warming of the Mediterranean Sea as a result of climate change. Among the proposed preventative measures is a salinity barrier in the Suez Canal in order to reduce the number of Red Sea aliens in the Mediterranean.

Will R. Nomadica spread as north as the Ionian Sea and further north along the Italian coasts?

Watch this very short video below to see for yourself how jellyfish are threatening Israeli Power Plants: It's quite astonishing!!

More on the spread of the nomad jellyfish in the Mediterranean:

An alien jellyfish Rhopilema nomadica and its impacts to the Eastern Mediterranean part of Turkey

Alien Species in the Mediterranean Sea

Mosquitoes on the Move as Climate Changes

As already hinted from my previous post, I will be looking at mosquitoes!

Most of us, have at least once in our lives been bitten by one or more mosquitoes. We all know that mosquito bites are itchy and are rather uncomfortable when trying to sleep. Although, the effects of these bites are unpleasant, we never expect these bites to cause us any serious harm or severe illness in Europe. However, scientists have warned that the number of harmful diseased mosquitoes spreading across the European continent is on the rise bringing new public health surprises!

Asian Tiger Mosquito
(Aedes albopictus)

In Europe, the Asian Tiger mosquito (Aedes albopictus) is an invasive species that has the potential to transmit infectious diseases such as dengue and chikungunya fever. The mosquito is native to the tropical and sub-tropical areas of Southeast Asia (Caminade et al.2012). 

However, over the last couple of decades, owing to increasing international travel and the global transport of goods, the Asian Tiger mosquito has invaded many countries around the world and has been ranked as one of the “World’s Worst” invaders by the  Global Invasive Species Database. 

These mosquitoes have the ability to out compete and completely eradicate other species with similar breeding habitats, as they lay drought-resistant eggs (Benedict et al. 2007). This is what makes this invasive species so dangerous!

As well as many other incidents, the Asian tiger mosquito was responsible for the outbreak of Chikungunya fever that occurred in the Italian province of Ravenna, summer 2007 (Enserink 2007). More than 200 people were infected with the disease (ECDC 2007). Scientists have investigated these recent outbreaks and have related them to the wetter and warmer climate patterns over central Europe (Gould et al. 2010). 

The map below shows the known distribution of the Asian tiger mosquito in 2011.

Known distribution of A. albopictus based on field observations from the ECDC/VBORNET
project (December 2011)

So what impact will our warming climate have on the spread of infectious disease carrying mosquitoes?

Through the use of regional climate model scenarios for the future and high-resolution observations, scientists from the University of Liverpool have investigated the suitability of Europe for A. albopictus by using both recent and future climate conditions (Caminade et al. 2012). The results showed that during the 1960-80s, northern coasts of Spain, Italy and southern France were climatically suitable areas for the establishment of these mosquitoes. The main finding of the study showed that over the last two decades climate conditions have become more suitable for the mosquitoes over central northwestern Europe and the Balkans, whilst they have become less suitable in southern Spain and areas around the Mediterranean basin (Caminade et al. 2012). 

Future trends show a similar pattern with climate suitability for mosquitoes increasing over northern Europe (including southern UK) as winters become warmer and wetter. In contrast, conditions appear to become more unsuitable over southern European countries such as Spain and Portugal, as more droughts are predicted in these areas in the future (see figure below).  

 http://171.66.127.193/content/9/75/2708.full.pdf+html. The left column depicts the mean suit- ability based on the ensemble mean of all RCM-driven projections for 2030–2050. The right column shows the future changes (2030–2050) with respect to the 1990–2009 climatology.

 

Several other studies modelling and mapping the distribution and survival of Asian tiger mosquitoes across Europe, such as those carried out by Fischer et al. (2011) and Medlock et al. (2006), show similar distribution trends across Europe. Large areas of western and central Europe that are inappropriate for the species today are projected to change during the 21st century towards a climate that can support the survival of the species.

Thus, climate change is affecting the distribution of mosquito populations and thus the spread of infectious diseases across Europe. It is clear that in the future, unintended anthropogenic introduction can be expected as a constant source of insecurity. European health officials must be prepared and ready to tackle future epidemics of vectorborne and waterborne infectious diseases.

Climate change will have enormous implications for human health in the future.

Further Reading:
Is Climate Change Aiding the Spread of Disease?

Sorry!

I just wanted to excuse myself for my lack of blog posts over the last week and a half. Having caught the dreaded flu over a week ago, I have only just recovered! However, being ill has inspired one of my next blog posts-here's a clue...

Snake Plague

Having received my new issue of Geographical today, I read a short article that stirred my interest. The article was about the dramatic increase in spider population on the Pacific island of Guam. What was fascinating was that the single accidental introduction of the brown tree snake 60 years ago, managed to wipe out 12 species of native bird. As a result, the island lost almost all its insect-eating birds allowing spider populations to thrive (Rogers et al. 2012).

Brown tree snake

I don't know about you, but I find it astonishing how a few snakes can eliminate almost an entire islands indigenous bird population in such a short space of time?

I suppose, Guam can be described as a text book example of what alien invasive species can inflict on an ecosystem. When the snakes were first introduced to Guam, the indigenous birds did not fear snakes and there were no predators to maintain the snake population. The island was a snake "paradise".

I delved further into the snake situation and discovered that there are an estimated 3,000 brown tree snakes per square mile on the 30 mile long island (National Geographic 2012).

A new research paper published in PLOS ONE (an open access paper, yay!) is one of the first papers to examine the impact of bird loss on the scale of an entire forests. Biologists from the University of Washington, Rice University and the University of Guam, lead by Haldre Rogers,  compared the density of spiders webs on Guam with the density of webs on the nearby Marianas Islands. They discovered that Guam has 40 times more spiders than any of the surrounding islands! Such astonishing results highlight how previous, small-scale studies underestimated the impact of bird loss on spider density as demonstrated by Guam- a large-scale natural experiment.

           Map of the Mariana Islands

(All forest birds are functionally extinct on the island of Guam, whereas relatively healthy bird populations remain on three nearby islands of Saipan, Tinian and Rota.)

 

 

 

It seems unbelievable that the effect of one invasive species can change the way in which biologists study and understand alien species interaction with ecosystems.  

So if you have arachnophobia I would not recommend a holiday to Guam!

Alien Species of the Week!!!

Red-necked wallaby
(Macropus rufogriseus)

Alien Species of the Week: 

 Red-Necked Wallaby

Whilst researching for this blog I was surprised by how many alien species there were that I hadn't even considered! So I thought I would briefly introduce a new alien species each week to show just how widespread and varied they can be.

This week I'm focusing on the Red-necked wallaby (Macropus rufogriseus). Originating from eastern Australia and Tasmania, this marsupial species was first introduced to Britain in 1975, with two pairs taken from Whipsnade Zoo. By 1993, the population grew to 26 individuals. This small colony of red-necked wallabies can be found on the island of  Inchconnachan, Loch Lomond, Scotland.

Today, it is estimated that over 100 red-necked wallabies live and continue to thrive at four different sites across Britain, including the Isle of Man.

Although, they make an exciting tourist attraction, some environmentalists argue that these feral colonies of wallabies should not be allowed to thrive in Britain. Red-necked wallabies can damage the natural habitat by feeding on native plant species and are able to outcompete native species.

However, whether these small populations of wallabies are really a big threat to British wildlife depends on each individual’s opinion!

Below I have linked a short video by the BBC about the Scottish wallaby colonies-enjoy!!!

Scottish Wallaby Colony to Move On

Welcome!!

As indicated by its title, this blog focuses upon the impact of Alien species upon the Earth's environments. However, when I speak of "Aliens" I'm not taking about the green creatures in a Steven Spielberg blockbuster, nor the fearful looking monsters seen in Alien vs. Predator, but rather a species occurring in an area outside of its historically known natural habitat.

As the world becomes increasingly globalised and travel and trade expand, humans have both intentionally and /or unintentionally facilitated the movement of invasive species across the globe. As a result, alien species that become invasive are considered to be the main direct drivers of biodiversity loss at a global level. Many scientists and environmentalist consider these invasions as a threat and regard them as a form of "Eco-terrorism".

To fully understand the impacts of alien species on the Earth's ecosystems and how they are helped by climate change, I will in this blog discuss past aliens species invasions and how coupled with climate change they led to the past global decline in megafauna. I will also discuss the natural and anthropogenic factors which are causing alien invasive species to become more common in our ever globalising world. As well as invasive species, I will also discuss the impacts of animal introductions to foreign environments e.g. islands.

Finally, the aim of this blog is to not solely investigate the negative impacts invasive alien species have on the environments they invade but also the positive affects these species can have on ecosystems,

 

I hope to entertain you along this alien voyage of discovery...

 Aliens out, Locals in!

This short video gives a quick overview of the drastic affects alien species can have on an environment: