The ever changing dynamics of biodiversity

May 29 2014 Published by under [Biology&Environment]

Biodiversity is a hot topic these days. By any measure (species counts, genetic diversity, etc.) we appear to be losing it at rates that are uncharacteristic for our current climatic conditions. That is to say, there have been other major extinction events in Earth's history, but our current predicament is not the result of asteroid impact, and ice age or massive volcanic eruptions. Rather, evolution has produced an animal capable of exploiting planetary resources on an unprecedented scale.

But I'm not interested in getting into a climate change discussion today. I don't suffer the deniers of anthropogenic change on a global scale. What I would like to address stems from a conversation this morning that has long been an issue for me. It started simply:

I remarked that lion fish are hardly unusual for classic invasive species that enters a new ecosystem and takes off as food items are plentiful and parasites and predators are not. There's hundreds of examples of this exact pattern playing out, even if most people will only be familiar with ones involving larger animals. But the discussion got a bit more complex and it is here that I have been thinking a lot recently:

Our planet is a complex and very dynamic place. It's a question of scale and most people focus on a scale that they can relate to. When we talk about the disappearance of species, 99% of time we're talking about things that were present within our lifetimes and are either highly restricted in their distribution now, or gone. It's a time frame we can wrap our heads around.

But the planet is more dynamic than that and sea level change, land mass movement and global temperature have fluctuated dramatically over time. We are so hyper-focused on preserving the current status quo or re-establishing the very recent past that it is easy to ignore the fact that biological invasions are the norm at a geological scale, not the exception. I'm not advocating for ignoring human-induced biologic invasions or the short-term havoc they cause on an ecosystem but it's important to keep them in context. We've made the situation worse, but "invasives" are not new. Not even close.

As an example that concerns me, we are rapidly approaching a time when there will be unobstructed ocean flow through the Arctic for much or all of the year. The lack of ice cover for longer periods significantly alters what can live in Arctic waters and current patterns are likely to move Pacific species east*. This is not a situation where we have a single species showing up and bullying a naive ecosystem, but the collision of two ecosystems that have been physically separated for a long time. It'll be the rough equivalent of submerging the isthmus of Panama (no, not the panama canal, which flows through fresh water).

Again, both of these dramatic events have happened before over geologic time. But in stark contrast to worrying about the fate of a single species or the preservation of a particular forest or reef, which is where much of our current conservation effort is focused, we will stand witness to forces far more dramatic. Unlike the lion fish eradication effort in the topical Atlantic, there will be no hope to put this genie back in the bottle**. But as noted here, we still think of conservation as stopping the changing of the tide:

Now I realize this is a fairly rambly post written in multiple interrupted sittings, so I want to make clear I'm not against studying invasive species or using invasions as a model for projecting ecological impacts and niche shuffling. But I do think we need to view species mobility and biodiversity as a dynamic processes, albeit one that is being driven mightily both directly and indirectly by human activities. In fact, I think such research is going to be key to figure out how we mitigate some of the damage. But what we view as an "ideal state" for biodiversity may not be the stable state for the environment in the future, no matter how much we try and force it to be.

*Anecdotally, there are already some disturbing reports here.

**Okay, there's no hope to eradicate the lion fish from the Caribbean either, but this is a different level of crushed hope.

7 responses so far

  • katiesci says:

    This is so far out of my field but I find it fascinating. Great thought-provoking post.

  • pyrope says:

    I completely agree with your assessment of problems with conservation and restoration baselines...but, I haven't seen much in the way of alternatives proposed either. I think part of the problem in the US is that our main conservation legislative tool is the Endangered Species Act. Which, by definition, has a single species focus. There is a fair bit of talk towards managing for diversity because it improves ecological resilience (hypothetically), but beyond that goal and ESA, I think this is a pretty sticky problem.

    As an aside, there is ongoing debate/discussion in invasion ecology literature about whether and how 'alien invasive' species should even be defined. i.e. should we be distinguishing between expanding the 'native' range vs. species introduced into a novel range. There are some very specific ideas in invasion ecology (targeting pathways of introduction, biocontrol, hypotheses related to difference in native/invaded biotic & abiotic conditions) that, I think, necessitate some continued separation. But, other components (dispersal) need not separate the two groups. Okay, that was a long aside.

  • Naj says:

    I've always thought it strange that the field of 'invasion biology' (however they define themselves) defines things as invasive if humans mediated their spread. I've also found the whole thing kind of odd, because, as you say, on a geological scale almost everything has migrated! So really, people studying 'invasion biology' are just studying examples of rapid migration/extensive gene flow, etc. I like your point about bringing whole ecosystems together (not just particular species) and what the implications may be. Curiously, this reverts us somewhat to the time before complete continental breakup -- where presumably there was much more freeflow between ocean waters, and among land masses.

  • proflikesubstance says:

    I'm both fascinated and terrified at the prospect of a Pacific species slosh over into the Atlantic. I think we're going to be hearing a lot about movement of things into the Beaufort Sea much sooner than we would like. I'm already hearing some rumblings about the macrofauna.

  • pyrope says:

    @Naj Like most forms of global change though, there's a huge difference in scale between a geologic baseline of normal long-distance introductions and human mediated introductions. Depending where you look, 4-6 orders of magnitude.

    More fun thoughts about loss of Arctic sea ice related to invasion - I've heard a number of folks at APHIS express concern about what it will mean if a bunch of Chinese goods start getting imported directly to the Northeast US instead of going through LA ports...New York/New Jersey climate/ecosystems are much more similar to much of China than LA is - so how many more unintentional pests & pathogens will we be introducing directly into suitable habitat?

  • proflikesubstance says:

    Compared to the natural invasion of the Pacific into the Atlantic, I imagine that'll be relatively small potatoes. Though, a new mechanism for land-dwelling invasives isn't great news.

  • pyrope says:

    Wood boring forest bugs come in primarily via pallets and packing materials, and are a big risk for northern forests. The asian long-horned beetle is a prime example.

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