What Exactly Does Ecosystem Collapse Mean?

The transition of a coral reef to an algal reef as a result of bleaching and overfishing is one of the most readily identifiable examples of a local ecosystem collapse (Image Credit: Stop Adani, CC BY 2.0, Image Cropped)

Fifth of countries at risk of ecosystem collapse, analysis finds

It’s a bleak headline, and one which was plastered all over my Twitter and Facebook feeds at the start of this week. I’m used to grim news about the environment. It’s part of my job. So there’s nothing particularly surprising about this title.

What it does represent though, is another use of a somewhat sensational term that is ill-defined by scientists and poorly understood by the public. We’ve written about such terms in the past, biodiversity and functional extinction being two examples. Here, I’m referring to ‘ecosystem collapse‘. I get the draw to such a term: people need to be alarmed about climate change and the ongoing loss of biodiversity our planet faces. Ecosystem collapse sounds really alarming.

So I thought I’d swim around in the literature a bit and see if I could figure out what we mean when we talk about ecosystem collapse.

Luckily enough, the first paper I came across is a relatively recent publication by Dr. Lucie Bland of Deakin University, which aimed to create a standardised definition of the term. Dr. Bland has done a lot of work with the IUCN Red List (more on that later), so this was pretty much a goldmine. Bland and her team’s definition early on in the glossary is deliberately vague, and a fair chunk of the paper points out how difficult it is to create a standardised term across a range of ecosystems. It goes like this:

[Ecosystem collapse indicates] a transition beyond a bounded threshold in one or more indicators that define the identity and natural variability of the ecosystem (Bland et al2016). Collapse involves a transformation of identity, loss of defining features, and/or replacement by a novel ecosystem. It occurs when all ecosystem occurrences (ie patches) lose defining biotic or abiotic features, and characteristic native biota are no longer sustained.

Bland et al. (2018) Developing a standardized definition of ecosystem collapse for risk assessment, Frontiers in Ecology and the Environment, https://doi.org/10.1002/fee.1747

So basically, ecosystem collapse occurs when an ecosystem undergoes a complete change which is potentially irreversible. It’s a pretty reasonable definition considering the amount of subjectivity that ‘ecosystem collapse’ actually covers. Let’s leave the subjective for later though, and look at the objective facts first. Almost every type of ecosystem is characterised by different species, and each ecosystem’s health is defined by different indicators. You wouldn’t use presence of hollow trees to assess a coastal strip, and you wouldn’t use water quality to assess a woodland.

The same can be said for similar ecosystems in different parts of the world, eg. a freshwater lake in Uganda and in Norway. And the same can even be said in two similar ecosystems managed by two different government bodies. Ecosystem managers aren’t always going to use the same metrics to define what makes an ecosystem ‘healthy’. Some may use ‘abiotic’ factors, like soil chemistry or presence of heavy metals. Others may rely on the presence of ‘indicator species’, species which indicate good ecosystem health when they occur at a certain abundance.

This all plays into the subjective notion of these terms. People often like to think of nature as having objectively ‘correct’ states. This just isn’t the case. Baselines shift all the time, and what we consider today as an ecosystem’s ‘normal’ state might be far from what it actually looked like two hundred, two thousand, or two hundred thousand years ago.

I’ll get back on track though. What I’m trying to say is that ecosystem collapse is a subjective term, defined by human perceptions of a number of aspects of the environment. The definition of ecosystem health will vary widely depending on who you ask. There’s nothing inherently wrong with this if you have a clear goal. Many organisations choose one ecosystem, region, or species to focus on, even though there are more severely threatened counterparts out there. But if you’re a larger scale organisation – like a federal or state government or the IUCN – and you need to provide reports that cover a complex network of ecosystems, having a standardised definition for their health and risk of collapse certainly helps.

So Is There a Standard Definition?

Bland’s proposal for standardising the definition of ecosystem collapse calls for better definitions of initial states of ecosystems, indicators of ecosystem of health, and thresholds defining the collapse. The study included an analysis of the literature related to ecosystem collapse, and found that many papers which concerned ecosystem collapse don’t have clear definitions for at least one of the three.

This is the Aral Sea now, the only ecosystem thus far to have been defined as ‘collapsed’ (Image Credit: Phillip Capper, CC BY 2.0)

In 2017, Bland’s work with the IUCN Red List of Ecosystems produced a quantitative guide to measuring ecosystem health. The Red List of Ecosystems is analogous to the IUCN Red List of Species. The Species list classifies levels of threats to species, the Ecosystem list does the same for ecosystems. The Species list currently uses ‘Extinct’ as its most dire metric, the Ecosystem list uses ‘Collapsed’. Bland and many of her co-authors came up with a series of quantitative metrics regarding habitat destruction with which they could classify the status of the world’s ecosystems. You can see the results of their work at the interactive map linked below, including the Aral Sea, one ecosystem which is now widely regarded as having collapsed. The Sea is now reduced to a series of lakes as a product of severe irrigation in the 20th century, and many native species are now extinct.

IUCN Red List of Ecosystems: Assessments

Ok, So What’s This A Fifth Of Countries Stuff?

As with Insect Armageddon in 2018 and the Two-Thirds of Wild Animals claim in 2016, the title that many newspapers ran at the start of the week is overblown and somewhat misleading. Don’t get me wrong, the situation is still horrifying. It really is.

The report referenced in these articles is by Insurance Group Swiss Re. That it’s by a Swiss insurance company doesn’t detract from its validity at all – it’s great that international organisations are finally seeing the economic catastrophe that a damaged planet can cause. Here are the most interesting findings:

  • Over half (55%) of global GDP is dependent on biodiversity and ecosystem services (this deserves more attention, but not right now)
  •  In a fifth of all countries, ecosystems that make up more than 30% of the entire country area are in a fragile state

Is it what the newspapers reported? Not really. Is it horrifying. HELL YES IT IS.

Basically, the report re-affirms that in a fifth of countries, there is a real risk of collapse for ecosystems that make up a large part of that country’s total area. This means that they could soon transition from what they look like now to something markedly different, like a vibrant coral reef to a grey algal reef, or a diverse floodplain to a trickle surrounded by farmland and hydropower plants.

Again, for a better overview of what brings about collapse, I encourage you to check out that interactive map that I linked above.

And now that you’ve read this, go and watch David Attenborough: A Life On Our Planet. Best bring the tissues though.

Sam Perrin is a freshwater ecologist currently completing his PhD at the Norwegian University of Science and Technology who got way too emotional watching David Attenborough’s latest film this week and is writing this as a form of catharsis. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.


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