Tuesday, 26 November 2013

Get involved!

You don’t have to be a highly qualified professor to contribute to furthering the scientific understanding of invasives! Citizen science is an exciting and fulfilling way that everyone can get involved in research, making a real difference to the knowledge of invasive species distributions (e.g. Gallo and Waitt, 2011). Currently there are many citizen science programs being implemented throughout the country that you can personally contribute towards such as Conker Tree Science and PlantTracker. All that is necessary is that you report your sightings of invasive species!
Thanks to a range of Smartphone apps available to download for free, participation couldn’t be easier! The apps provide excellent high resolution photos, enabling you to identify and report the sightings of invasives wherever you are. The information received is then saved to an online database which maps the species, location and time of sighting. This data can then be used to assist scientific research.

Apps downloaded from Apple App Store
It is encouraging to learn that approximately 100,000 members of the general public are already getting involved with citizen science across the UK (Feilden, 2013). If you're yet to give it a go, then I highly recommend downloading an app suited to your geographic location today!

Thursday, 21 November 2013

Why the bad press?


More often than not invasive species are portrayed in a negative light; this is fuelled by both the research of ecological conservationists and by personal experiences of recreational gardeners. I have also put a large emphasis on the need to remove invasive species and prevent the introduction of future invasives throughout my blog. Before I progress any further, I feel that it is necessary to present the basis for this school of thought by outlining some of the key ways invasive species can have a negative impact on the environment.
Predation
Prior to the introduction of an invasive species, a given ecosystem is likely to be at an equilibrium state with an established food web. Invasions have the potential to introduce a new predator to the ecosystem, which will consequently alter the population dynamics. In particular this could have extreme consequences if the invasive species preys on a keystone species. Predation may also result in the loss of endemic species. When the Brown Tree Snake was introduced to Guam in the late 1940s it had a devastating effect on the island’s bird populations. The snake was associated with the extinction of at least seven avian species from the island, some of which were endemic, and was also linked to a decline of many other bird species (Pimm,1987).
Competition
Water, nutrients, minerals and light are just a few of the resources that are often essential for life. What’s more is that these are often limited, and despite differences in the relative requirement of resources between species, there is often interspecific competition to acquire them. It may not come as a surprise to you that invasive species are often very strong competitors. For example the Himalayan Balsam (mentioned here), has the ability to outcompete a variety of plant species that may also be present along the canal edge, excluding other organisms and decreasing species richness (Hulme and Bremner, 2006)
Perhaps a less obvious way that invasive species can drive biodiversity decline is via competition for reproductive mates, leading to hybridisation (Mooney and Cleland, 2001). During the 1950s the Ruddy duck was introduced to the UK from North America. This species can sexually reproduce with the native White-headed duck population. Unfortunately, the reproductive behaviour of White-headed duck females indicates a sexual preference for male Ruddy ducks, resulting in an increased incidence of hybridisation and a decline in the native endangered population (Green and Hughes, 1996). Consequently wide scale culling programmes have been implemented across Europe to reduce Ruddy duck populations (NNSS).
Disease
As invasive species move around the globe, they may also act as disease vectors, transporting potential harmful pathogens to new geographic locations. If animals, plants and humans are not equipped with the appropriate immune response, then transported diseases may have severely detrimental effects. There is increasing research into whether the presence of certain invasive species can have a negative effect on human health as result of associated pathogens (e.g. Allan et al., 2010). 
I hope that these examples help to illustrate just some of the reasons why the Millennium Ecosystem Assessment highlighted invasive species as one of the major drivers of biodiversity decline. Furthermore, not only do invasive species have an ecological impact, but they also have an economic impact. Surprisingly it is estimated that as much as $137 billion per year is spent controlling and compensating for the effects of invasive species populations across the USA (Pimentel et al., 2000). 
I will leave you with this video, explaining that as a consequence of the negative effect on biodiversity and human health, the EU is currently proposing to implement a ban on the future intorduction of invasive species...




Until next time!
Elena

Sunday, 17 November 2013

Invasives of Camely Street Nature Park

Here’s a little insight into what my friend Katherine and I have been up to this week at Camley Street Nature Park, just down the road from UCL…




Yep you're looking at two of the newest volunteers for the Wildlife on your Waterways project, co-ordinated by the London Wildlife Trust! We had an excellent morning meeting the team whilst getting a tour of the site, and as an added bonus I also stumbled upon some great material for this weeks blog.

Camley Street Nature Park is home to a large pond which hosts a variety of aquatic plants, birds, insects and fish throughout the year. However, over the recent years chicks and fish have been predated on by an invasive species which lurks below the surface, can you guess which one?


Ok, so that is a near on impossible task! Instead, think back to the early 90s when Teenage Mutant Ninja Turtles were on TV, did you ever fancy raising your very own Ninja Turtle sidekick which could fight off extraterrestrial Aliens? Well you weren't the only one! As a consequence of the hit TV show, the numbers of terrapins (in particular the red-eared terrapin) imported from the USA to be kept as pets in the UK went through the roof. However, instead of fighting aliens, the owners actually brought in aliens! The unsuspecting TMNT fans were not ready for their baby terrapin to grow to up to 4lb and live for as long as 40 years. So when the novelty of owning a "hero in a half shell" inevitably wore off, terrapins were dumped into water ways around the country (Vaughan, 2013).


Photo taken from Patel-Carstairs, 2013; Photo: ALAMY

But how did the terrapins make their way to Camely street pond?


Photo of regents canal taken from the nature park


You can just about make out from the photo that Regents canal (left) is the main water source for this pond (right). In general canals provide a super network for terrapins to move around the country until they can find the perfect habitat such Camely Street Nature Park, where the urban environment creates a 'heat island effect' (London Wildlife Trust, 2013). Interestingly, it is thought that the future terrapin populations may thrive due to warmer summers as a consequence of climate change (Wilkinson, 2013). Potentially creating a big problem for native species in the coming years! 

There is currently ongoing research into the terrapin population of Regents Canal. You can help increase scientific understanding by ensuring that you report any terrapin sightings to the Canal & River Trust (customer.services@canalrivertrust.org.uk). 

Learning about that terrapin population of Regents canal has highlighted to me that man-made transport systems as another way that humans have facilitated the spread of invasives. Additionally, with Kings Cross St Pancreas railway station just around the corner from the park, there is even international links for terrestrial species to hitchhike around the globe!

Another invasive species that I was interested to discover whilst exploring the nature park was the Japanese Knot Weed - these articles (1, 2) are worth a quick read just to show how destructive this species can really be!

Plus if you want to find out more about the great work that London Wildlife Trust are organising down at Camley Street Nature park then checking out my friend Katheirne's blog is an absolute must - she's written an excellent post titled "A Field Trip, and Gardens in the City"

Have a good week!

Thursday, 7 November 2013

Legal Aliens (Part 2)

Organisms are often restricted to their native location due to physical barriers, therefore humans are largely responsible for the spread of invasives around the world. However, despite putting the blame on humans in one of my earlier blog posts, it is important to realise that naturally occurring global change events can also facilitate the introduction of invasive species. If barriers to invasion are removed as a consequence of natural global and environmental change, I wonder if it could be argued that these species are ‘legal’ aliens? Hence the Sting inspired title of this blog post. Let's take a look at a specific example...

The ocean dominates the globe and accounts for approximately 70% of the total surface area, creating a huge barrier for organisms in their quest to invade new locations. To argue that the ocean should be fully removed to enable species to spread naturally is as ridiculous as it sounds! However, the Earth is a dynamic system and you may be surprised to hear that the movement of  tectonic plates can result in the removal of the ocean barrier at specific locations around the world. Such an event occurred approximately 3 million years ago, when movement of the Earth’s tectonic plates joined North America and South America by a thin strip of land, referred to as the Isthmus of Panama


Letter A points to the Isthmus of Panama (Google Maps)


The formation of this land bridge between the two continents is a historically and geographically important event, and lead to the Great American Interchange (GAI) (Wallace, 1876). Prior to the formation of the Isthmus of Panama, numerous invasive species had already become well established in North America. This could not be said for South America however, where few invasive species had been introduced, meaning that there was a high proportion of endemics present (Marshall, 1988).

During the GAI, evolutionary distinct aquatic and terrestrial organisms were able to expand their range, resulting in reciprocal invasions between North and South America. Marshall (1988) studied the movement of land mammals throughout that GAI and calculated that in total 38 genera walked across the Isthmus of Panama from South America to North America, and 47 genera walked from North America to South America. This exchange is thought to be in equilibrium when the size of the source fauna present on each continent before the GAI is taken into consideration (Marshall, 1988).

Species: Cuvieronius. Moved from North America to South America during the GAI
Photo Credit: Sergiodlarosa

A consequence of the GAI was that a large proportion of South American endemic species were exposed to high levels of competition and predation for the first time. It is interesting to note that since North American genera reached South America 3 million years ago, there has been further diversification, and today approximately half the genera present in South America have evolved from North American species. This did not occur in North America (Marshall, 1988).

This example shows that invasives can have a dramatic effect on the species composition of non-native ecosystems as a consequence of natural global change. Additionally this interchange could not have been prevented, therefore my personal opinion is that despite the impact that natural invaders have, if they are introduced as a consequence of past or future global change then they should be considered 'legal'.

Sunday, 3 November 2013

Legal Aliens

Good morning! 
I was just listening to the radio and this song gave me a great idea for my next blog, which I will publish later on this week. Stay tuned, and in the mean time I hope you enjoy a relaxing Sunday!





(Englishman in New York by Sting - released in 1987)