Category Archives: Extinction

Post-2020 Global Biodiversity Framework: 3 pitfalls to avoid when setting ecosystem targets

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Nations of the world will meet in May to negotiate a new Global Biodiversity Framework (GBF) under the Convention on Biological Diversity. It’s a big deal because this framework will define global aspirations for protecting species, ensuring benefits from ecosystem services, reducing pressures on nature, and making biodiversity governance more sustainable.

Part of the post-2020 GBF includes explicit targets for what we hope to achieve in the next decade. Devising these targets is an arduous process, where every word is chosen carefully after hours of negotiation. Using the word ‘and’ instead of ‘or’ could cost millions of dollars in government budgets. Even worse, the wrong word could potentially lead to the permanent extinction of species that have been around for millions of years.

It makes sense that at least one of the targets for the post-2020 GBF should focus on ecosystems. After all, no plant or animal can exist in isolation. Now, while I won’t be so brash to propose my own ecosystem targets, I would like to point out three pitfalls that should be avoided once government negotiators come together at the next COP meeting.

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Scepticism towards the Living Planet Index is unwarranted

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The most recent Living Planet Report was released last year, which showed that vertebrate populations around the world have declined by 68% on average. At the time, Brian McGill wrote a post at Dynamic Ecology expressing his scepticism over these large declines. His doubts stemmed from several related papers, which all showed that vertebrate populations tended to be quite stable on average. While some populations have declined, most have remained stable and others have actually increased.

My understanding of Brian’s message (and the messages of the published papers supporting him) was that while humans do affect vertebrate populations, these effects are not consistently negative. Instead, some species benefit from human actions, so human’s ultimate legacy will be rearranging relative population structure, rather than causing wholesale declines.

While I agree with this interpretation, I worry that it is causing unwarranted mistrust of the Living Planet Index. I was reminded of this last week by a passing comment by Mark Vellend:

“If biodiversity seems intractable, then just think about recent discussions of the Living Planet Index, which is based on pretty simple underlying data.”

His remark was in the context of his post suggesting that ecologists have subconscious biases that cause us to exaggerate how much humans harm biodiversity. Ecologists probably do have subconscious biases, but the Living Planet index shouldn’t be used as evidence of this.

I don’t believe the Living Planet Index exaggerates population declines. However, I also recognise that populations are stable on average. This probably seems contradictory, so I’ll use the rest of this post to explain why it isn’t.

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Trump’s Wall could affect 350 species of amphibians, reptiles and mammals

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I originally started writing this post two years ago, back when Donald Trump had just been elected as President of the USA. I didn’t finished writing it then because I assumed that the topic was just a passing fad, something none of us actually took seriously. Fast-forward to today, the US government has been shut down for more than three weeks as Trump tries to hold the country hostage over his border wall with Mexico. I suppose now is a as good a time to finally publish this post, even though a paper was published on the topic in BioScience last year.

As one of the most absurd campaign promises in recent history, Donald Trump’s commitment to building a wall between the United State and Mexico has attracted many critics. Many scoffed at his claims that such a structure will keep out the make-believe mob of bad hombres chomping at the bit to sell drugs to innocent Americans. Others giggled at Trump’s conviction that those very same bad hombres would pay for his trademark erection.

But this post is not about the fragile justification for building a massive wall. It’s a thought experiment on how many species would be affected by this cross-continent barrier.

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Long-term monitoring generally underestimates negative trends in biodiversity

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Modern conservation and environmental management rely on data. Unless you can actually show cold, hard evidence of natural deterioration, you open yourself up to criticism from denialists and other eco-skeptics. It is too easy for industry lobbyists to dismiss conservation recommendations as tree-hugger scare-mongering.

So conservationists, being the idealists that we are, decide to gather evidence for downward trends of various aspects of biodiversity. Unfortunately, efforts to quantify biodiversity trends are a major challenge. Not because measuring trends in diversity is particularly difficult, but rather because long-term monitoring is susceptible to sampling artefacts.

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Handling cumulative impacts during the environmental decision-making process

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Although ecology doesn’t have many general laws, one most likely to qualify is the species-area relationship. If you walk through a field in a straight line and count all the different species you come across, you’ll notice that the total number of species increases as you progress along your straight path. After a while, however, you’ll start seeing the same species over and over again until you eventually find that you’re no longer spotting any new ones. This is the asymptotic species-area curve. While the exact mathematical form of the relationship is still hotly debated, it is safe to assume that it is an increasing function that reaches a plateau once all the species have been encountered.

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