Monday, 9 February 2015

Ecosystem Services To Suffer Under Invasive Impact?

Been a while since I've been able to pen a post, some inconvenient examinations took up a lot of time over the past couple of months (I learnt so much about carbon sequestration after wildfires that I didn't even get to write *cries*). I was planning to re-launch the blog on WordPress, but that hasn't happened yet and it probably won't for a while....

In any case, I've had time now to put something together, taking a look at the potential impact of invasive species on ecosystem services, using a recent example from Montserrat (Peh et al., 2015)

If you're thinking 'what is an ecosystem service?' it's a fairly straightforward concept, essentially referring to the benefits that an ecosystem provides to humans. A lot of these can be very important, both locally (like food provision) and on larger scales (such as carbon sequestration *painful memories*)

The term is being increasingly used in academic literature , having been popularised by the Millennium Ecosystem Assessment in the early 2000s. The Google Ngram graph below shows how it's usage has really taken off.
In addition to the term's growing usage, there is growing concern that invasive species may negatively impact ecosystem function, thus the services they provide.

So, to Montserrat! Located in the sunny Caribbean, Montserrat may seem like a great place for a holiday. However, half the island is an 'exclusion zone' following a devastating volcanic eruption in 1995. The island also has a growing problem controlling invasive species, which is what the recent study is more concerned with.

In Montserrat, local stakeholders at the Central Hills forest area (Fig.1) are concerned that invasive feral goats and pigs may trigger a chain of events that causes native vegetation to by replaced by alien plum and guava trees.

Fig.1 Map of Montserrat, highlighting the study area
This, of course, will have knock on impacts for the animals of the ecosystem. For example, consumption of native lobster claw plants causes the loss of nests for the Montserrat oriole, an endemic bird which attracts nature tourism (look how cute it is, I'd like to see one)
A Montserrat oriole. Straight up 10/10 but critically endangered.
Staying on the subject of nature tourism, the opportunity to view our feathered friend and walk in the cloud-shrouded tropical forest is a great attraction to international tourists. A survey was carried out on tourists to the Central Hills asking them if they would still visit if the ecosystem was substantially altered by invasive and endemic biota were lost.

In 2009, the reserve made an estimated $419,000 from nature based tourism. The survey revealed that only 54.3% of tourists said they would still visit the reserve if the invasion substantially altered the forest, representing a loss of income of $192,000 per year.
Central Hills. Worth a visit I'd say.
Another service that could be impacted in an invasive takeover is carbon sequestration (nooo not again...). It is estimated that the total carbon stock of the forest is currently 341,000Mg and would shrink to 302,000Mg under the invasive prevalent state.

Taking a Carbon price of $83.61 per tonne, the benefit of maintaining current forest structure would be over $3,000,000, and of course, there would be a little less carbon dioxide in the atmosphere. The resolution of the study is low though, so there is little confidence in this statement.
Trees: sucking up CO2, and savings
Overall, control of feral livestock and suppression of invasive plants in the Central Hills would result in a net benefit of $214,000 per year. Cessation of feral livestock control would reduce benefits to locals (via harvesting wild meat) and global beneficiaries (tourism, carbon sequestration) and would likely cause the disappearance of native species in the reserve. Basically, failure to control invasive species = everybody loses.

In an attempt to manage the 'all-round loser' situation, hunting of livestock has been undertaken since 2009. However, long term funding for this endeavor has not yet been secured. From an economic viewpoint, Peh et al have shown that it needs to continue.

Montserrat has been devastated by a recent volcanic eruption and its ecosystem services in the north of the country are threatened by invasive species. Control needs to be undertaken, the only issue now is who is going to pay for it.

Finally, if invasive species are threatening services in Montserrat, it makes it more likely that services will suffer elsewhere if similar disruption to ecosystem functions occur. Another reason to be wary of invasive species then...

Over and out


Friday, 30 January 2015

My First Poster Presentation

Life is full of big firsts. First steps. First kiss. First time you got drunk and threw up in front of everyone at prom on your 18th birthday (Ok, that last one might just apply to me...)

Recently though, I experienced a new first. My first academic poster presentation. It may not be life defining, but it's definitely been an interesting process to work through, so I thought I'd give my perspective on it as a Masters student doing one for the first time.


We were informed that our poster should be on future anthropogenic environmental change, linked to an element of environmental dynamics, such as Phosphorus, land slides, soil erosion and so forth... we were required to create the poster, which we would then present to the rest of the group.

Naturally, I decided to pick something invasive related.  Invasive plants it turned out to be.

At first, I figured I should just conduct research like I would if I were to write an essay. So I found a bunch of decent looking recent papers, made my notes and had a fairly good idea what I wanted to write.

Then I decided to actually write an essay. I felt that this would help me create a structure, which I could then transfer over to my poster directly, without losing too much wordage.

I had information, but I didn't really know what to do with it in terms of presentation. So,t he next thing I did was look at some of the posters in the department. I also had a read of the British Ecological Society guidelines for creating posters, to get a different perspective. They suggested putting my Twitter handle on it, but my tweets are probably 90% football related (I should really get a separate account for academic-y stuff).

In any case, here's a version of one of the first things I put together....

At this point I thought great, I have created something full of information but it probably needs to be tidied up. I was also lacking a reference list and certain personal information which needed to be added.

But I was still not sure if this is what a poster should be like. So I asked for the opinion of some people who know more about posters than me. The general feedback I received with that my poster was too verbose (at about 600 words), to lead people into the topic but not to be overly detailed.

I was also told about a prize winning poster, with a grand total of 30 words. THIRTY. I did not dare to cut my word count by that much though!

I did, however, hack away with the aim of removing superfluous words, whilst still trying to maintain the same level of information.

I became aware though, that by doing this it would be making certain aspects of the poster more difficult to interpret for people that perhaps may not be so familiar with the topic. Additionally, I did have to remove some information.

But rather than let that fall to the cutting room floor and end up in waste disposal, I thought I should provide additional information on this very blog, which is what I did here. 

After taking away a lot of words, and rearranging the design a bit, the final poster I created looked like this.

A crucial difference between this poster and my previous offering is that I no longer have to squint to read it! I also decided to use bullet points as an effective away to more clearly highlight individual points. I also simplified the aims and introductory information and added a reference list, in the smallest font I dared to use, so as not to take up too much space.

I then began thinking about what I was going to say in my presentation. I figured we might be required to speak for 5-10 minutes, so this was what I aimed for initially.

However, we were then informed that we would only have two minutes each to talk.

My initial reaction to that was something like this:

How was I meant to put across all the things I wanted to say in that short amount of time?! I haven't actually given the talk yet but my last attempt was two minutes thirty seconds, so I'll need to try and become more concise in the coming days.

It seems a shame to me that we don't have longer to talk, but if that's the way things are going in academia, then it's good that we're doing it in that style.

So that's about it for the poster I have created, but I'll leave you with some general feelings.

One big point I'd like to make is I wish we had done a poster in my undergraduate degree. From what I hear, the format of creating a poster and giving a talk for a couple of minutes is becoming more and more popular.

When we did our undergraduate dissertations, I was fortunate enough to present my work to the year group below me in the form of a powerpoint presentation, but many people never got a chance to show off their hard work and efforts to a wider audience. Also, i'm finding there's a big difference between preparing to give a powerpoint, and presenting a poster.

We were in groups of about four or five per supervisor. It might have made a nice tutorial assignment maybe to create a poster (not an A0 beast, even just A3 would be good for the practice) and present it to the people in the rest of the small group. That's just my two cents anyway...

Thanks for reading


Thursday, 20 November 2014

Invasive Plants and Anthropogenic Environmental Change: Will Europe Soon Be Losing Its Rag Over Ragweed?

One of my assignments in the Masters course I'm doing is to make a poster on the theme of future environmental change. Me being me, the topic I chose was how invasive plant species will respond to anthropogenic environmental change. So without further ado, here's what I found out...

First some basic background information...

Invasive plants are non-native plants that spread and rapidly dominate over native species. Over the last century, the number of invasive plants has increased rapidly in many regions as global trade and travel have become more frequent (Vicente et al., 2013).  In recent decades invasive plants have impacted nearly all ecosystems and ecologists have increasingly recognised invasive plants as a major threat to native biodiversity.

Invasive plants compete for space, nutrients, water and light with natives and affect soil, water and light conditions. This can lead to replacement of diverse communities with a single invasive species. Vila et al (2011) showed that in 1041 field studies, invasive plants reduced native plant growth by 22.1%, abundance by 43.5% and diversity by 50.7%.

So as we can see, invasive plants could potentially cause a lot of serious issues, but how will they respond to anthropogenic environmental change?

Well, making predictions around this topic is a daunting task. Plants react to many climatic aspects including temperature, precipitation, length of frost free periods and magnitude and variation of extreme climates. The figure below gives an idea of of the many different forces that can affect invasions and also suggests that a positive feedback could occur with increasing invasions.

Impact of global change on invasions, and feedbacks from invaders to global change.
Climate change is expected to impact 5 key elements in the invasion process (Hellman et al., 2007): pathways, environmental constraints, distributions, impacts and management effectiveness.
The consequences of climate change for the invasion process.
In summary here are some of the things we can expect:

  • Human transport will increase propagule pressure of some invasive plants, possibly beyond thresholds that permit establishment. 
  • Some currently marginal invasive plants will be able to successfully colonise new areas if conditions become more similar to their native range. 
  • Cold-temperature constraints on invasive species will be reduced at their higher-latitude or upper-elevation range limits. Warm-temperature constraints on invasive species will increase at their lower-latitude or lower-elevation range limits. 
  • Relative impact of some invasive plants will increase when the abundance of natives decreases. 
  • Finally, the tolerance of some invasive species to some herbicides will increase (e.g., due to increases in CO2), making management more difficult
We can also expect some other impacts: 
  • Increased temperatures and CO2  may disproportionately favour the spread of invasive plants to new regions as they have traits that help them adapt to new climates. such as rapid dispersal and evolutionary change (Maron et al., 2004), tolerance of a wide range of climate conditions and lack of dependence on co-evolved pollinators (Dukes et al., 2009; Sheppard and Stanley, 2014). 
  • Climate change is also likely to lead to more frequent disturbance in ecosystems, from events such as wildfire, drought and storms (Bellard et al., 2013; CCEW, 2008).  This can also benefit the establishment of invasive species as native species will become stressed (CCEW, 2008) the ecosystem’s resistance to invasion will lower. If keystone species are lost, invasion vulnerability will dramatically increase (Zavaleta and Hulvey, 2004).
  • Additionally,, climate change will affect phenology (Wolkovich and Cleland, 2014). Many invasive species flower later or earlier than natives. Theories around fluctuating resources and opportune invasion periods may be critical. If natives don’t track shifting climate, climate change may create phonological vacant niches which promote invasion success. 
Phenological impacts on invasion. Invasive plants should invade when other species are inactive.
I always like to include examples when talking about topics like this, and to illustrate how climate change could affect invasive plants, I found a cool model of projected increases of ragweed across Europe.
Ragweed: Doesn't look like much of a threat...
Again, first some background information...

Ambrosia ortemisiolia (Common ragweed) is an annual plant which originates from North America (Storkey et al., 2014). It first reached Europe in the mid-19th century. However, rapid spread did not begin until the 1940s due to growing transport networks and contaminated seeds. The plant is highly invasive and rapidly spreading in Europe from its established areas in France, Austria, Hungary and Croatia.

Its pollen is highly allergenic to ~5% of Europeans (Richter et al., 2013), with health problems including hay fever, atopic dermatitis and asthma. A single plant produces 50,000 seeds (Brands and Nitzsche, 2007) and 1 billion pollen grains (Fumanal et al., 2007) and warming has been shown to increase pollen loads. Once established, control is labour intensive and expensive so there’s an urgent need to evaluate spread potential

To evaluate the possible impacts that climate change will have upon the range of Ambrosia ortemisiolia, a process based model incorporating growth, population dynamics and competition was utilised by Storkey et al (2014). Process based models are a useful tool for this purpose as they have the ability to capture interactions between climate change, land use and plant competition at local scales. 

Results of the model show that the European distribution will increase under future climate change. There is a risk of the population spreading to the United Kingdom and Denmark as growing conditions become more favourable. No southerly spread is predicted as lower future rainfall will make Spain, Italy and Greece climatically unsuitable.  This is shown in the figures below; there are a lot more areas that are highly suitable to ragweed in the bottom set of maps, which are for the future, compared to the top maps representing current conditions.

A: European distribution of common ragweed. B: Potential range under current climate. Orange areas are well established, yellow areas suitable for casual populations and blue areas are highly unsuitable.
A: Potential ragweed range in Europe from 2010-2050. B: Potential ragweed range in Europe from 2050-2070. Colour codes are the same as above.
So why is any of this important? And is there anything we can do about it?

Well, the level of management, likely to involve physical or herbicidal removal, will vary by country and have a large bearing on the impact of establishment. The species is ruderal and its persistence requires regular disturbance in the habitat, hence land use factors will be key to the spread.

Furthermore, Richter  et al (2013) produce evidence that a thorough, well executed management plan involving surveys and eradication can drastically inhibit ragweed spread and reduce allergy costs. A cost benefit analysis reveals that total savings from managing ragweed from 2011-2050 range from €9-11 billion for current to extreme climate changes. Without management, mean allergy costs could be as high as €365 million annually for Austria and Southern Germany with an annual temperature increase of 0.04 °C from 2011-2050.  

Those are big numbers, and given that the model discussed before showed that ragweed will soon be much better suited to large swathes of Europe than it is currently, it's not just Austria and Germany that will have to consider the potential economic impacts ragweed could cause them. The UK could also be facing the negative impacts of ragweed establishment unless we have plans in place if it becomes a more common species here. 
So will Europe soon be losing its rag over ragweed? Potentially yes, but time will tell..

Overall. climate change is likely to increase invasive plant prevalence. However, as with most things climate change related, the issues is far from clear-cut. Responses will vary greatly between species and locations (Corlett and Wescott, 2013). Furthermore, how we manage invasive plants under climate change will be key to the impacts they have.

Over and out

The Invader Inspector