A final farewell!

Over the past few months, I have been creating weekly blog posts exploring Invasive Alien Species and developing a deeper understanding of their importance with regards to the wider world we live in, but sadly it has to come to an end! 

My prior knowledge led me to believe that all Invasive Alien Species are bad and a major cause of extinction and habitat destruction across the world. Although these characteristics are true for some Invasive Alien Species such as Banana Bunchy Top Virus or Himalayan Balsam, I have learnt that this is not always the case. For instance, with the acoustic battles between native and invasive frogs in Florida, it led to the native populations altering their calls to survive alongside the new Cuban frogs entering the environment. I did not expect such adaptive behaviour to occur so rapidly and for an Invasive Alien Species to be able to enter a new habitat with such little influence.


Additionally, Dornelas et al. studied how diversity changed within biomes across the world and found no overall decrease in biodiversity. They found that despite increasing extinction levels caused by Invasive Alien Species and habitat destruction, amongst other things, there was no distinct overall decrease. It was suggested that this could be due to hybridisations occurs from invading species and shifting distributions of species due to climate change. Again highlighting the fact that Invasive Alien Species may not be as toxic and detrimental as I first thought.

Unfortunately, such successful coexistence and hybridisation is rare, and the spread of Invasive Alien Species appears to be increasing speedily. Over the past 12 weeks of research, my blame for the negative effects caused by Invasive Alien Species has shifted away from the invading species themselves, towards humans. With increased trade and transport efficiency/quantity, more Invasive Alien Species are being involuntarily spread around the world. Also, the dramatically changing climate, presumably induced by increased fossil fuel consumption, has led to more opportunity for invasions to occur. Therefore, human actions appear to be both directly and indirectly, the main cause of the increase in invasions and destruction worldwide.


Following this development of my opinion, I explored ways in which humanity can try and prevent further damage to both ecosystems and biodiversity and control the Invasive Alien Species already in action. It was highlighted throughout, that controlling them requires both cooperation between countries and between governments and the local people to successfully eradicate problematic species, a much wider scale than I originally assumed. With human populations exponentially growing, we are spreading and invading every part of the globe's surface. Are humans, in fact, the biggest Invasive Alien Species of them all?


Well that's all for now, I hope you have enjoyed learning more about Invasive Alien Species with me and that it has inspired you find out even more!!

Taking control of Invasive Alien Species!

Invasive Alien Species are becoming increasingly widespread and common across the world,  and it is thought that soon, they may take over habitat loss as being the number one cause of ecological destruction. But fear not, scientists and governments are working together to find ways to prevent and eradicate invasions!

Clout & Veitch define two main priorities when trying to minimise further damage to the environment and biodiversity. You can either reduce the risk of new invasions or eradicate the existing invasive populations, both of which are extremely difficult tasks. By either preventing or eradicating Invasive Alien Species (IAS), it can help to increase biodiversity but can also provide economic benefits by removing the causes of agricultural losses for instance. However, the complex dynamic of ecosystems and their species within, make it very hard to successfully do so. 

So how can we successfully eradicate IAS?

There are multiple actions that can be taken to increase the chance of successfully removing an invasive species, as suggested by Pluess et al. For instance, by starting a removal campaign before the infestation gets uncontrollably large or starting to eradicate within the first four years of invasion and by putting focus on IAS that arrive via cultivation. Also, once the removal has begun, ensuring it goes to completion, that species are removed above the rate of reproduction, and the entire population is being accounted for will help to promote success, as explained by Clout & Veitch. 

Invasive Alien Species associated with agriculture are more likely to be eradicated because of economic losses associated when invasions take over, like with the Banana Bunchy Top Virus explored in last weeks post. Also, invasions on islands are more likely to be successfully removed due to the smaller infestation area that is easier to manage. 

EU Regulations

All eradication plans require a lot of cooperation between local people and governments. For instance, on January 1st, 2015, the European Union made a new regulation requiring a list of concerning IAS to be created, prevention methods to be put in place and management schemes set up to quickly eradicate widely spread IAS. It is these large scale plans that improve eradication success by providing larger investments and overall increased efforts although this isn't always enough! 

Issues with Invasive Alien Species eradication!

Despite teams of scientists working to create schemes for eradicating Invasive Alien Species, when they are carried out, it usually doesn't go according to plan.  The outcome of an eradication scheme depends on very special features of both the invading species, the environment surrounding it and fellow inhabiting species. 

 Clout & Veitch explore some of these issues, for instance, eradication success depends on the how the IAS disperses. In plants, for example, if they are spread by wind or birds then their seeds could distribute across a very wide, varying landscape and it is hard to prevent this from happening and fully eradicate certain species.  

Similarly, it is very hard to design eradication techniques that do not harm non-targeted species. On Kapiti Island, brushtail possums (shown to the right) were successfully eradicated, but in the process, 181 birds were also killed in the same traps. This can cause a lot of controversy as members of the public and some organisations, question the ethics of killing a native species in the eradication process of an invasive one. 

However, there is also opposition when it comes to killing the Invasive Alien Species itself.  For instance, the culling of the ruddy duck in England sparked a lot of debate in terms of ethics, as noted by Blackburn et al. Negative responses such as this can jeopardise the progress of eradication schemes and therefore this social aspect also needs to be considered during the planning stage. 

At the end of the day, eradication schemes do involve killing or removing invasive animals, plants or micro-organisms and this is sometimes quite hard to accept. Before exploring Invasive Alien Species throughout this blog, I would have instantly assumed that the eradication of an innocent organism was immoral and avoidable. However, after discovering the major impacts that IAS can have on habitats and their animals within, I've learned that control and elimination can be the lesser of two evils and result in fewer deaths overall. In spite of this, there are steps that we can take to prevent invasions from occurring to prevent lives avoidably being lost. With increasing global transportation and a changing climate, it is our responsibility to reduce the chance of future extinctions and take responsibility for the effects we have.

Do you think its okay to kill entire populations of plants, animals and microorganisms when they may have invaded an area due to humans?

Check out this blog related to marine conservation to see why it is important to prevent more native species loss http://the-turtle-and-the-hare.blogspot.co.uk!

Can we beat the Banana Bunchy Top Virus?!

Banana growing countries across the world are at risk of invasion from the boisterous Banana Bunchy Top Virus!

 

Surprisingly, Invasive Alien Species can come in the form of micro-organisms, like the Banana Bunchy Top Virus. First recorded in Fiji in 1889, it has now invaded more than 120 countries worldwide, and scientists are trying to find a way to control this dangerous disease and prevent further spread in banana plants! 

What does this dreadful disease actually do?

The classic symptoms of infected banana plants include an overall dwarfed effect, bunching up of leaves, lack of fruit production and dark green streaks on the leaves, as reported by Kumar et al. In the image below, the 'In' shows the infected plant compared to the healthy 'He' one. 

The stunted growth and reduced fruit production cause detrimental economic and health effects. Worldwide production of bananas exceeds 100 million tonnes, and it is the 4th most important food crop behind rice, wheat and maize according to Cook et al., making it fundamental to millions of livelihoods. 

What is the main mechanism of invasion?

The Banana Bunchy Top Virus (BBTV) either gets transmitted by the aphid, Pentalonia nigronervosa (as shown by the image to the right) or by infected plants coming into contact with healthy ones. In Hawaii specifically, Almeida et al. believe that the movement of contaminated plant material across and between the islands led to this epidemic destroying large amounts of their crops. 

Almeida et al. describe the human transportation of these plants to new sites, both with and without the aphid being present upon them, as a type of Pathogen Pollution. This invasion of virus' into places outside their native area cause the host (the banana plant in this case) to be at a new risk of infection and hence human activity is causing major spreads of diseases and not just in the banana plant! 

With the world's population size continuing to grow rapidly, the demand for food is ever increasing meaning that more banana plantation sites are being formed. The set-up of theses farms requires the transfer of crops from previous areas, and this is where the cross-contamination occurs. Also, as mentioned in another blog post, improved transportation efficiency is allowing plants, animals and micro-organisms to spread to new invade-able areas meaning that diseases like BBTV can spread even more easily thanks to our increased trading and travels. Bananas generate both an income and a food source for people all over the world and so the management and control of diseases that destroy them is highly important, but how is it done? 

Methods of management?

The Cooperative Extension Service of the University of Hawaii says there are two ways of controlling such a disease either by killing the aphid's that carry the disease of removing all the infected banana plants from a particular site. 

For the Banana Bunchy Top Virus in Australia, Cook et al. predicted the amount of area that would be affected by BBTV if no management strategy was enforced (Nil Management) vs, a plan of Active Containment. This Active Containment plan involved destroying any previously infected crops and as soon as the infection was detected locally, to stop further spread. As the graph to the left shows, the Active Containment reduces the amount of land diseased drastically, with the variance shown being due to the risk of re-emergence and eradication is not 100% effective. 

However, these plans and policies are very effective in theory but when it comes to practising them, it is never as successful. For instance, in 1993 in Australia a five-year programme was carried out to eradicate Banana Bunchy Top Virus but did not fully work and by the end, not all of the disease was removed and so spreading began again. 

In sub-Saharan Africa BBTV is also widespread but due to different socioeconomic conditions, long-term, wide-scale programmes like done is Australia are as suitable, even if they did become entirely effective. As a result, Kumar et al. proposed some new ideas on how to control BBTV in sub-Saharan Africa:

• Educate farmers on how to efficiently destroy diseased crops 
• Supply clean, BBTV free planting material to farmers 
• Improve monitoring schemes 
• Deploy rapid removal responses to the detection of the disease 

The schemes suggested are not mutually exclusive but can be used together to detect, destroy and prevent re-infection in plantations efficiently. Such epidemics require cooperation between the governments, local authorities and the farmers themselves in order stand any chance of effective control.

 Do you do think the consumer has any responsibility for making sure they buy bananas from farms that actively try to reduce the spread of BBTV? Should this information be made available?

Whatever your view,  next time you buy a banana, just remember how lucky you are that that one escaped the grasp of the famous Banana Bunchy Top Virus!! 

Climate - the game changer?

'Climate change' is a phrase thrown about by the media and scientists, commonly used to explain the weird and wonderful things that are happening on Earth today. But what affect is it having on Invasive Alien Species?

What does 'climate change' mean?

According to the Metoffice, climate change is:

"A large-scale, long-term shift in the planet's weather patterns or average temperatures."

and the results of this can be seen across the world. For instance, since 1901 there has been a 0.89 degree Celsius rise in the average surface temperature, global sea levels have risen 19cm since the 1900's, rainfall patterns are changing with a major increase in the mid-latitudes of the Northern Hemisphere and Arctic sea ice has reduced 4% since the 1970's.
These telltale signs of climate change, amongst many others, have major impacts on all organisms. But what affect is it having on Invasive Alien Species? Hellmann et al. defined five key consequences that climate change is already having or is expected to have in the future. 

1. Altered transport and introduction methods: 

As previously mentioned in my blog 'Transport and Trade of Invasive Alien Species', how Invasive Alien Species get to new areas is really important. Not only is it changing due to increased transport efficiencies but rises in sea levels mean previous unconnected areas are being joined by water. Also, melting of sea ice means that new shipping routes are becoming available and shipping seasons are being extended meaning more opportunity for pesky species to hitch a ride. 

2. New Invasive Alien Species: 

Non-native species that were not previously unsuccessful at invading, may be able to inhabit new areas that now have climates more suitable to them. Also, Invasive Aliens Species are known to be able to be able to survive in changing environments, where are native species are not as good. With longer dispersal ranges, more tolerances and a shorter juvenile period they are more likely to survive when the going gets tough! 

3. Altered impact of the previous Invasive Alien Species:

The impact an Invasive Alien Species can have, once fully established in an area, is commonly restricted by environmental factors such as temperature and water. For instance, a temperature constraint set by the extreme cold may mean an Invasive Alien Species is unable to survive in winter, allowing the native species to recover and spread. However, with temperature increases, the growing season may be extended, reducing the recovery time of the native species and could result in their extinction. 

4. Altered distribution of the previous Invasive Alien Species:

With changes in climate, the landscapes also change, and the spread of Invasive Alien Species responds to this. Bellard et al. for example, predict that species are likely to move away from lower latitudes due to the already extreme climatic conditions that are likely to become unbearable. This is expected to lead to a loss of tropical Invasive Alien Species but a movement to more temperate mixed forest areas in the Northern Hemisphere. Its already being seen with a reported 76% increase in the number of Invasive Alien Species in Europe in the last 30 years. 

5. Change to the effectiveness of control strategies: 

Check back soon to find out more about this and how scientists and governments are trying to combat the issue of Invasive Aliens Species through control, such as the chemical spraying shown to the right. 

So why is all this climate change occurring? Click the link to find out some more information: http://www.metoffice.gov.uk/climate-guide/climate-change/why

Also, to find out how climate is affecting human health, check out this other blog https://unhealthyplanet.blogspot.co.uk! 

Death of the Dodo

The extinction of the famous flightless bird of Mauritius, the Dodo, tells the sad tale of the effect humans can have when they to colonise another country! 

The Dodo, Raphus cacullatus, used to be found on the isolated, volcanic island of Mauritius, in the middle of the Indian Ocean, as shown by the map to the right. This tiny island was first discovered by the Portuguese in 1507 but did not become popular until the Dutch arrived in 1598, as explored by Gold et al. 

What did the Dutch do?

In 2006, Julian P Hulme created a full account of the history of the Dodo and aimed to solve any of the myths created due to the lack of evidence associated with this fluffy friend. From this he noted that before 1620, there were many Dutch accounts of the Dodo but after this is drastically reduced. Initially, people thought that the hungry sailors that arrived on the island after weeks at sea were to blame, as they'd go for the biggest, easiest to catch food that they could find. As well as Dodo, there was also a rich supply of pigeons and parrots that supposedly tasted nicer and therefore the predation pressure from humans was slightly reduced, meaning that that was not the sole cause of their extinction. 

Unfortunately, however, when the Dutch sailors arrived they didn't just bring themselves, they also brought lots of exotic invasive species that would continue to cause absolute havoc. Hulme explains that in 1600 monkeys were brought over, in 1606 goats, cattle and pigs and finally in 1639, deer made their way on shore. All of these invasions were very successful, being the Dodo's first predator and eventually lead to their extinction in 1662. The pigs were thought to have been the most detrimental due to the habitat destruction they caused and them feeding on the eggs or chicks of the Dodo. 

But that's not all! The colonisation of humans lead to the destruction of the Dodo's home, and feeding on small vertebrates, nuts and fruits, they were very reliant on a large area of land to live off as Gold et al. found through reading Dutch sailors diary entries. This dependence on the forest and the fact they could not fly to escape the invasion lead to their demise. 

It wasn't even just Mauritius!

Sadly, the colonisation of Rodrigues, an island 560km East of Mauritius, saw the extinction of their very own flightless Rodrigues solitare bird due to human activity as explored by Gold et al. As noted in previous posts, islands are at the most risk to extinction from the introduction of Invasive Alien Species and this a classic example to prove this. Their isolation and unique ecosystems leave them very vulnerable to outside influence. So was it the human's fault? Or was it just an unfortunate circumstance? 

Mauritian Identity

Despite the sadness generated from the loss of this bizarre bird, Mauritian people still continue to love and cherish it as part of their culture and identity. Meet Sharvanee Mauree, my best friend and house mate at university who was born and lived in Mauritius until moving to London to study here at UCL. I asked what the Dodo means to her,  and she replied...

"I think it's a symbol of being Mauritian. It's on our passports and all official documents and it's funny because none of us have seen it in real life. I think in a way it's a sign of what we have lost and whether we can preserve the rest of our wildlife now, that's for us to decide!"

Beastly Bullfrogs!

American Bullfrogs around Western North America are being labelled as one of the major causes of amphibian decline! 

The American Bullfrog, Rana catesbeiana, is becoming of great scientific and conservational interest as studies shine light on its impact on native populations of amphibians, especially frogs. With this new information, scientists are hoping to be able to manage this species and potentially eliminate the negative effects it has all together. 

Figure showing the worldwide distribution of the American Bullfrog 

So where have they managed to get to?

Over the years, this Invasive Alien Species has been introduced to over 40 different countries. The world map to the left shows the native distribution in grey and the non-native, introduced areas in black. As you can see, these famous frogs originate in Eastern North America and have managed to spread to areas of Western North America, South America, Europe and Asia due to human transportation and habitat modification.  

Why are they so destructive? 

American Bullfrogs are causing mayhem amongst native frog populations and Blaustein and Kiesecker repeatedly found that at sites where Red-Legged Frogs were absent, American Bull Frogs would be found close by. So what were the Bullfrogs doing that was so detrimental? 

Their studies showed that the American Bullfrog was basically eating the Red-Legged species. At both the tadpole and adult stage they recorded the Bullfrogs feeding on other amphibian species, especially the Red-Legged ones. The middle image to the left shows the scale of the American Bullfrog tadpole compared to the Red-Legged one on the image below that. 

However, this wasn't the only thing that was going on! Sometimes, as a response to the arrival of the American Bullfrog species, the Red-Legged ones would change their microhabitat, possibly by moving somewhere else in the water or changing their feeding habits. Unfortunately, in some cases this pushed the native frogs into an area where they were at increased risk of predation by fish, which in turn reduced the population numbers. 

Similar to this, Kiesecker and Blaustein found in another study that the time took for Red-Legged tadpoles to reach the metamorphosis stage increased and the body mass reached by the end of metamorphosis decreased when in the presence of American Bullfrogs. As a result the Red-Legged frogs that did survive were smaller and less competitive. 

But wait, there's still more!! American Bullfrogs are also causing damage through transmitting the fungus Batrachochytrium dendrobatidis which causes the infectious disease Chytridiomycosis. Greenspan et al explored how this disease does not always lead to death in all species. Unfortunately for the Red-Legged frogs, the disease is lethal and American Bullfrogs are unaffected by it and therefore they act as vectors that spread the disease to new populations they invade.   

   

Have humans had an impact?

Unsurprisingly, yes we have! Blaustein and Kiesecker found that habitat modifications made in Western North America actually led to more optimal conditions for the growth and success of the Invasive Alien American Bullfrogs. Converting large ephemeral wetlands into smaller permanent ponds, possibly though the development of infrastructure, creates prime breeding grounds of the Bullfrogs whilst removing the preferred spaces for other amphibian species. 

Also, American Bullfrogs only made it to places like Europe and Asia through the pet trade and accidental transport, a common way Invasive Alien Species are spread, as mentioned is last weeks post. 

To see The Simpsons experience with Invasive Alien Bullfrog species, click the link 

https://www.youtube.com/watch?v=g3V0wJ3q7l0

Transport and Trade of Invasive Alien Species!

Humans have managed to spread to nearly every corner of the globe, but how have they effected the distribution of Invasive Alien Species? 

As the world becomes more accessible for humans, it also does for other organisms. From species hitching a ride, disturbance of environments and the exchange of non-native species between countries, increased trade and transport has led to more invasions.  

At what point did it start to change? 

Philip E Hulme defines 3 key points in time that have caused a notable change to the spread of Invasive Alien Species: the end of the Middle Ages, the start of the Industrial Revolution and the Era of Globalisation. The Era of Globalisation has been marked with both increased income growth and  transport efficiency with both of these factors having an impact on the spread of non-native species. 

Graph showing the relationship between Alien Plant Richness
and Gross Domestic Product 

Increase income growth

Hulme explores the link between Invasive Alien Species richness and the Gross Domestic Product (GDP) of both continents and islands as displayed by the graph to the left. As GDP increases, so does amount of non-native species. The relationship is also stronger for islands, probably because of increased quantities of merchant imports which transport greater amounts of non-native species. 

Increase transport efficiency

The Industrial Revolution and advances in technology have seen a massive increase in the amount of travel that occurs worldwide. Increases in both personal transportation and global trade has had a knock on affect on invasive plants, animals and microorganisms.
Since the 1970's there has been a four fold rise in the volume of global imports that occur and 46% of this involves dry cargo. The dry cargo, mainly transported by containers, pose threat with Invasive Alien Species hitching a ride both inside and outside the containers and ships that transport them.

Also, between 1984 and 2000, 725,000 pests were recorded entering into US ports and 73% of this was via airports rather than seaports.

Disturbance due to transport!

Increasing demand for transport leads to the creation of more roads, railways and a rising use of waterways. As a result habitats get destroyed to make way for this infrastructure and the surrounding areas are continually disturbed and it allows organisms to travel to areas they may have not previously have been able to reach. Hansen and Clevenger compared the number of non-native species occurring in Canada along some railway lines and highways that were next to either grassland or forest. From this study they found:

• Grasslands had the higher frequencies of non-native species and there were more non-native compared to native species for up to 150m from the corridor edge 
• Forested areas had the lower frequencies and more non-native than native species for only up to 10m from the road or railway edge 
• The frequency of Invasive Alien Species decreased with distance from the corridor edge 
• The frequencies of non-native species along highways and railways was very similar 

These results therefore suggest that the transport corridors are having an impact on the distribution of Invasive Alien Species. Grasslands have shown to be more prone to disturbance than forested areas and non-native species are more able to successfully invade and stay there - which coincides with the idea I explored with Himalayan Basalm in my previous post! 

Graph showing the invasion success of
Wild-Caughtand Captive-Bred bird species 

Global exchange of exotic organisms! 

Interestingly, humans bring a lot of non-native species into other countries on purpose through global trade of plants and pets.  For example, exotic animals that are kept as pets and then escape and non-native plants that are introduced into garden centres, have more of an effect than you might expect. 

Carrete and Tella found that it is not the common caged birds that cause issues if they escape but the wild, exotic birds that are brought to countries through the pet market. The graph to the right shows how successful captive bred and wild-caught pet species are in Spain, where 0 = never seen in the wild and 3 =  breeding regularly in the wild. As it shows, captive bred species do not successfully manage to breed and get to level 3 and are therefore not a threat to the environment they enter. 

An example of a wild caught species that has successfully managed to invade places such as the US, Italy, Spain and Czech Republic is the Monk Parakeet, a bird imported from Argentina as shown to the left!

The ideas explored here are all raising questions when it comes to conservation. It is expected that the amount of transportation and disturbance to the environment is only going to increase in the coming years, so how do we make sure that the numbers of native species do not drop too low?

Click the link to find out more http://www.actionbioscience.org/biodiversity/simberloff.html