Inspecting Invaders: The Finale

Today is a sad day, for it marks the final stage of the Inspecting Invaders journey. We've had 21 posts along the way. There have been highs and there have been lows. Some witty titles and some terrible, terrible jokes. Overall though, I feel like a completely different person from when I came into this process...

...what do you mean this isn't the X Factor? I'm emotional ok...

It's been a long road... but we got there.

At the start of this blog, I set out to explore the impacts that invasive species have had within the context of environmental change. Though, quite frankly, I'm surprised anyone continued to read after my introductory ramble.

We've looked at everything from squirrels to invasive ghost fish, how we used to be invasive species and now, how we manage them. There have been problematic invasive species pretty much on my doorstep and on the other side of the world. Heck, there was even a quiz in there somewhere.

What have I gathered from writing this blog? Well, it may seem obvious but I'm going to reinforce it. Invasive species are a large concern in a variety of ecosystems; they have been in the past and will continue to be in future, as our global environment continues to change.

The funky wordle below also summarises the blog pretty well. Unsurprisingly, the words 'invasive' and 'species' feature heavily, so clearly (and fortunately) my occasional  frequent rambles didn't detract from the focus too much.

Other larger words include the brothers in arms 'et' and 'al', given the group nature of academic research. 'Change', 'impacts' and 'spread' also stand out, perhaps due to the fact that environmental changes can often be key facilitators of invasive species introductions to new areas and their expansion.

Additionally, the words 'negative' and 'positive' are both present in the wordle, highlighting the fact that invasive species do not always have adverse effects within a given environment. 

Where invasive species rank in terms of other issues our planet is facing is open to debate, but having read about their very serious consequences, in certain cases we should be very concerned indeed.

I have very much enjoyed writing this blog and I've learnt a lot at the same time. I hope you've found it interesting and enjoyed reading it too.

Over and out (and this time I mean it)

The Invader Inspector

Humans As Invasive Species, A Major Megafaunal Extinction Cause?

I was going back through some of my blog posts the other day, when I suddenly realised something that I can only describe as appalling.

It seems everything I've done do far has been a bit, well, contemporary. Today, I'm going to put that right, by taking a look at the megafaunal extinctions that took place in the late Pleistocene.

Starting with the general factoids, 50000 years ago, there were >150 species of megafauna. However, by 10000 years ago, at least 97 were gone (Barnosky et al., 2004). Species lost include the Diprotodon and the Mastadon. 

R.I.P. : The diprotodon, otherwise know as 'the giant wombat'.

There are a number of theories for what caused the extinctions, it seems highly probably that each continent experienced extinctions at different times, driven by different... drivers.

Observed and predicted extinction rates for each region. Source: Prescott et al., 2012.

Specific theories include: Climate change, overkill, blitzkrieg (rapid overkill), changes in the nutrient cycling (Faith, 2011).

But where does this fit into the context of invasive species?

Well, Barnosky et al (2004) speculate that the magnitude of extinctions in Africa and Central Europe where milder than elsewhere as humans co-evolved with megafauna there for hundreds of thousands of years. On the other hand, humans were an invasive species in the Americas and Australia.

Now this is interesting. Throughout this blog I've covered several examples of human facilitated invasions, but humans as an invasive species themselves seems like a very intriguing concept indeed...

The theory of humans as invasive species would explain the magnitude of extinctions in the Americas and Australia. The main extinction pulse in Australia came after human arrival and does not seem to match and many regional or global climatic changes (Barnosky et al., 2004).

Summary of megafauna extinctions on each continent. Source: Barnosky et al., 2004.

On the other hand, the theory fails to offer insight as to why any extinctions took place in Africa or why Europe lost 36% of megafauna (Barnosky et al., 2004).

And additionally, the Australian extinction chronology is highly uncertain. Analyses indicate that of 21 extinct megafauna genera, 12 persisted to at least 80000 years ago, and at least 6 persisted to 51-40000 years before present. The arrival of humans can only be said to have been in the range of 71.5-44.2 thousand years ago. Pretty large range there...

There are also situations where it seems climate change is a far bigger player in extinctions than any humans as invasive species cause.

For example, at least 24 large mammals are known to have disappeared from Africa during the Late Pleistocene. However, there is little reason to believe that humans played an important role in African megafaunal extinctions (Faith, 2014).

And briefly going back to Australia, new evidence throws human impact into doubt even there, with suggestions that climate changes, not anthropogenic burning, was responsible for changing conifer dynamics, which would have had a knock on effect on megafauna (Sakaguchi et al., 2013). Though at the same time, the authors do not rule out a hunting effect...

Not a burning issue in this case?

To conclude, the issue of humans as invasive species in the decline of megafauna seems to be incredibly complex. Indeed the relative importance of climate change and impacts of newly arrived human populations remains highly controversial (Prescott et al., 2012).

But hey, I'm sure that as our knowledge and dating techniques improve, the picture will become clearer.

Hope you enjoyed the journey back in time, next time we'll be back in the present day where I'll be wrapping the blog up :'-(

Over and out

The Invader Inspector 



The Walking Catfish, Running Large Risks in Florida?

Hi everyone, happy new year! There's been some decent TV on over the past couple of weeks with new episodes of Sherlock and Dr Who causing excitement for millions. For me, however, the highlight of the winter TV season came on Wednesday during Nature's Weirdest Events.

About two minutes in, Chris Packham starts talking about some unusual events that have taken place in Florida. It seems there have been fish casually walking about on land, as if it's where they belong... Check out the link above for the footage and humorous commentary from astounded Americans.

A walking catfish, out on the land.

According to Packham, the fish normally appear on land after storms, and their numbers are increasing yearly to what now amounts to a very high population.

But how can these catfish even survive on land, let alone walk on it? Well, it seems they have a special organ allowing it to take oxygen from the air. Handy, huh? And they can walk, thanks to their pectoral fins and tail, in the manner of a commando crawl. They can also survive several months without food.

Thanks to these adaptations, the fish have been causing numerous problems. And guess what? They're an invasive species! And listed as one of 100 of the worst invasive species at that (Lowe et al., 2000).

The catfish is native to Southeast Asia, but was imported to Florida in the 1960s by aquaculture farmers (National Geographic). Within 10 years, the fish had spread significantly within the state.

Worldwide walking catfish distribution...

... and the spread of the walking catfish in Florida. Source: Columbia.edu

A tropical fish farmer describes how he used to have 10,000 Rosy Barbs, but now, as a result of ferocious predation, all his pond seems to contain are walking catfish! It seems they move from pond to pond, making use of their unique adaptations, wiping out all the tropical fish. Sad.

Additionally, the invasion has happened quickly, so native wildlife has had little time to adapt and is suffering as a result. The walking catfish feed on other fish, invertebrates, amphibians and aquatic insects. The devastation is described as 'tremendous'. Damage caused by the walkers has cost millions of dollars (National Geographic).

All hope is not lost though. The walking catfish is predated by wading birds including herons and egrets, which means fewer native species are threatened than they otherwise would be.

Even so, it seems the walking catfish is running large risks to Floridian freshwater ecology.

Over and out

The Invader Inspector