Progress review

So far I’ve been writing this blog for the Global Environmental Change module that I have studied as part of the MSc Climate Change course at UCL. Tomorrow the module unfortunately comes to an end, so it seems that today is an appropriate time to review my blog. As someone who had never blogged before, I was apprehensive when I started and was unsure as to how the blog would progress. Looking back at my blog archive, there are some key themes that run throughout the posts which have helped me form my current opinion on invasive species. Here goes an attempt to summarise my blog…

Historically invasive species were spread around the globe by human transportation, although natural environmental changes also led to the introduction of some invasives. These species are most commonly known for the negative effect that they have on ecological systems however, perhaps the neutral or positive impacts just aren’t headline material. As a result conservation efforts have focused on preventing and eradicating established invasives, such as the Himalayan balsam. Some people have even tried to eat them out of existence! Despite this established invaders are often very persistent and survive, so scientists have promoted citizen science to try and gain a clearer picture of just how widespread invasives really are. In the present day it appears that human induced climate change is the new driver of invasives and ecological communities now consist of species from all over the world. Climate change primarily leads to the spread of invasives by causing species to change their geographic distribution in order to survive physiological stress induced by increased temperature. Additionally, changes in the physical environment will soon enable humans to transport invasives as far as the North Pole. Perhaps it’s therefore time to change our opinion on invasive species when we strive to protect global biodiversity.

On a final note I would like to thank everyone for their comments and feedback. It has been very encouraging and has helped me direct my blog to relevant issues. I hope to continue blogging throughout the rest of the year however, I apologise in advance if the posts aren’t as regular as they have been to date!

Thanks again,

Elena

UK floods 2014

I'm sure you will be aware of the devastating floods that have occurred across much of coastal Britain this January. Alarmingly the occurrence of extreme weather events is set to increase as a consequence of climate change (IPCC, 2013). Furthermore it seems that flooding is just another way that invasive species can be spread - check out this news story. I've posted this just to illustrate the growing amount of evidence that suggests it is no longer possible to prevent the spread of invasive species.

Time for change

Protected areas are established throughout the world to promote biodiversity and protect species from human activity. Not even protected areas however, are almighty enough to safeguard plants and animals from climate change; even in “natural” and “protected” systems unavoidable changes are taking place (Walther et al., 2002). Additionally, research has shown that species from protected areas are vacating them in refuge of cooler temperatures, which in turn provides empty niches for new species to invade (Gillingham). Walther et al., (2002) describes how current established communities often consist of species from all over the word. This increased understanding of the frequency and magnitude of species invasions around the world is summarised by the term "The Homogocene" (Rosenzweig, 2001). Although you may disagree, this suggests that me there are no longer “native” species and “invasive” species. 

It’s not surprising the recently released IPCC report indicated that climate change will continue to rapidly warm the planet into 2100. For this reason alone, I don’t think that it’s in the best interest of ecological conservation to prevent species from migrating to cooler temperatures. This is because research has already shown that if species cannot evolve to tolerate high temperatures in their current location, they suffer an increased risk of extinction (Thomas et al., 2003).  Thus, I think that such invaders should also be considered “legal aliens” in the same way as I described relating to the Great American Interchange.

Chris Thomas, recently released an article in Nature, urging people to rethink their views on 
global environmental change and invasive species. Despite the negative impact of invasive species, I was startled to read that Britain “has gained 1875, established non-native species without yet losing anything to the invaders”. Chris argued that we cannot stop change, and just because invasive species are new to the location which they arrive, it doesn’t mean we have to get rid of them. Although there is sometimes a need to try and eradicate invasives that have an extremely detrimental impact on ecological systems, Chris stated:

“It is a mistake to misdirect valuable and increasingly scarce conservation funds into unwinnable wars.” 

Personally I am in agreement with Chris Thomas, it's time to change our view on invasive species. Instead of eradication we should look to conservation methods such as habitat management to promote biodiversity. Let me know what you think.

Elena 

Country File

Just a quick post in case you are running out of TV to watch as the Christmas holiday comes to an end! I would highly recommend watching the latest episode of Country File - “Wildlife winners and losers”. Presenter Ellie Harrison takes a look at some of the invasive species in Britain and discusses the latest plans to reintroduce the Lynx back into the British countryside. Click here to watch it on BBC iPlayer, but you’ll have to be quick as it’s only available until Jan 12^th!

Removing invasive species

Whether it involves the use of chemical treatment, physically uprooting plants, or introducing biological controls, there are numbers projects in place to remove invasive species e.g.1, 2, 3. However, invasives are persistent and removal is expensive (Pimentel et al., 2000) so should not be done light heartedly. I found it particularly interesting that removing invasives may also have unexpected ecosystem wide effects (Zavaleta et al., 2001).

Macquarie Island is a natural heritage site, home to a variety of native plant species and seabird colonies. The story of what happened on this Island describes what can wrong if conservationists do not consider ecosystem processes and food web structure before removing invasive species…

Cats were unfortunately introduced to the island in the early 1800’s and rabbits were later introduced by sealing gangs in 1878. When the rabbits arrived they were preyed on by the cats and populations were kept at equilibrium. Despite this the population size was still large enough that rabbit grazing activity had an extremely negative impact on the vegetation. As a result the European Rabbit Flea was introduced to the island to further reduce the rabbit population and protect the native vegetation. The flea was effective and the population size decreased. However, the conservationists did not consider the implications that this would have on the cats, which developed an appetite for seabirds in the absence of rabbits! In response to this the cats were shot on the island, which obviously lead to an increase in rabbits! (Bergstrom et al., 2009)

This is not the only case where eradication has been hard. The Giant African Snail recently featured on BBC News for this exact reason. 

For those of you against invasives it therefore seems that prevention is more beneficial than eradication. Methods of preventing invasives can be read about here, and interestingly investment in prevention could save money in the long term (Leung et al., 2002)

This adds to the debate of whether or not we should allow invasive species that are moving north as a consequence of human induced climate change to establish or not. After all, invasive species can have a positive effect on the environment, but if we don't prevent them will it be too late to find out?

In the new year I’ll be posting my opinion on invasive species and climate change – in the mean time have a fabulous time celebrating the start of 2014!

Elena

Aliens Vs Climate Change

Could invasive species be driven by climate change?

In 2006 a team of scientists studied the distribution of terrestrial and aquatic organisms in Great Britain between 1960-2000. The researchers found that 12 of the 16 taxonomic groups studied shifted their range to high latitudes or altitudes (Hickling et al., 2006). Hickling et al., (2006) reasoned that during this period global warming was occurring and was likely to be a factor driving changes in species range.  More recently, a meta-analysis has been published revealing that species are migrating north of the equator at an average rate of 16.9 km per decade, or to a higher elevation at a rate of 11 m per decade (Chen et al., 2011). This is at least twice as fast as was previously predicted. Moreover, Chen et al. (2011) provided statistical evidence that these rates of migration are correlated to temperature change, indicating a direct link between species migration and climate change. 

Why move north? 

Generally speaking, as you move north or south of the equator there is a decline in temperature, similarly at higher altitudes the temperature cools. In other words, the warmest temperatures that put populations under the highest level of stress are nearer the equator. Adaptation to climatic stress takes place over many generations and if species cannot evolve fast enough then global warming may result in population crashes (Pounds et al., 1999). 

The Edith's Checkerspot is a particularly well studied butterfly species which excellently represents this change in geographic range over time. Parmesan (1996) found that net extinctions were greater for populations at lower latitudes than at higher latitudes (Fig. 1). This extinction gradient is what was expected if climate change was causing the range shift, as populations closer to the equator suffer from hotter temperatures. 

Figure 1. Left: Edith's Checkerspot. Photo credit: H. Stroo.
Right: Map of Edith's Checkerspot populations monitored between 1992-1996. Red indicates extinct populations. Blue indicates present populations (Parmesan, 1996)

Previously I defined invasive alien species as those that are introduced to a new environment and have a negative effect. Therefore if migrating species compete with exiting communities, climate change has the potential to directly facilitate the introduction of invasives! 

Until now attributing the cause of invasives to either human activity or natural change has been fairly straight forward. Climate change poses a slightly harder question. I think that the findings from the Firth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) are critical to this debate. Although climate change is affected by natural internal variation, one of the key focuses in this report was the increased certainty that humans are the main cause of recent global warming (Fig. 2). 

Figure 2. IPCC (2013)

With this in mind I'll leave you with one final thought. Do we have the right to prevent species from naturally migrating and invading new locations in order to survive global warming when humans are the dominant cause? If we are currently experiencing a 6th major extinction (Barnosky et al., 2011), should we in fact be letting these species establish in new ranges if it minimises the total number of species extinctions?

Until next time!
Elena 

Ecosystem Services

In my last post I mentioned ecosystem services; as a slight aside I thought you might be interested in this video which outlines the key ecosystem services. Hank Green puts particular emphasis on the human impact to ecosystem services as a result of biodiversity change. Whilst watching the video it's worth bearing in mind the effect that invasives had on the ecosystem services of South Africa - there are lots of similarities. Keep your eye out for the reference to invasive species towards the end of the video!