About Brian McGill

I am a macroecologist at the University of Maine. I study how human-caused global change (especially global warming and land cover change) affect communities, biodiversity and our global ecology.

Here we go again – the planet is practically dead

So the 2020 version of the Living Planet Report has been released to massive headlines blaring catastrophe. The central claim is that vertebrate (i.e. fish, amphibian, reptile, bird, mammal) local populations declined, on average, by 68% from 1970 to 2016 (the report is released 4 years after the end of the data). The authors of the report have done a much better job of getting out the notion that this is an average decline. IE they’re not claiming that there are 68% fewer vertebrate individuals on the planet, but that the average decline is 68% (but see footnote)*.

To invert their claim, the average vertebrate population in 2016 is 32%  (100%-68%) of the size that it was in 1970. If we look at the 2018 report it says that the average vertebrate population in 2014 is 40% of what it was in 1970. And the average vertebrate population in 2010 is 48% of what it was in 1970. So if a population in 1970 was of size N then, 2010=0.48N, 2014=0.40N, and 2016=0.32N. Wow! That is a 52% decline in the 40 years from 1970 to 2010, a 16.6% decline in four years from 2010 to 2014 and a remarkable 20% decline from 2014 to 2016. The math is a little complex because it is exponential, not linear, decline but that gives a 1.82% decline per year from 1970 to 2010, a 4.46% annual decline from 2010-2014, and a 10.6% per-year decline from 2014-2016. So not only are there huge declines, but the declines appear to be accelerating (admittedly with small samples for recent years). If we are conservative in the face of this accelerating trend and hold declines constant for the next 10 years (from 2016 so to 2026) at 10.6%/year and start in 2016 at 32% of 1970 numbers then we are down to 10% of the 1970 numbers by 2026. Do you believe that! In 6 years from now the average population will be just 10% of what it was in 1970. (To be clear, the LPI authors did not make this claim – I did, but it is just a 10 year extrapolation from their numbers). You would think such a decline would be more obvious to the casual observer. I’m old enough to remember 1970 and have spent a lot of time in the woods in my life. If there was a 20% decline (or increase) I’m not sure my fallible memory would reliable detect the change (in fact I’m pretty sure it wouldn’t). But if there were 90% less birds on average than my childhood, I would have thought I would have noticed. You would also think the world would be absolutely exploding with things vertebrates eat (e.g. insects and plants).

If this isn’t happening, then what is going on? Well for starters, it is pretty dicey to take short term rates and extrapolate them when things grow or decline exponentially. If you do that you are liable to find out everything is extinct or at infinity pretty quickly. So lets go back to the core claim straight from the report – there has been a 68% decline in the average vertebrate population since 1970. Not quite as extreme, but you would still think I (and a lot of other people) would have noticed declines in vertebrates of this extent not to mention the boom of insects and plants as they’re freed from predation.

If you don’t trust my fond recollections of my childhood nor my extrapolation to what should have happened to insects and plants (as you definitely shouldn’t!), then how about this. The LPI core result is completely different than other studies (not cited in the Living Planet Report for what it is worth). Several, like the LPI, track thousands of populations over decades. All (like the LPI) suffer from some observer bias – scientists have more data in temperate regions and near cities and for bigger animals, but there has been no evidence to date that this fact is biasing the results of any of the three studies. First, here is a plot very similar to the LPI plot but for invertebrates in the UK by Outhwaite and colleagues in Nature Ecology and Evolution:

Now this is invertebrates, not mammals, but what we see is 3 broad groups have abundances higher than they did in 1970 (freshwater species showing a spectacular recovery possibly due to clean water laws), and one broad group that is down just a smidge. The overall balance across all 4 groups is a 10% INCREASE.

Here is a paper by Dornelas and colleagues in Ecology Letters (disclosure I am a co-author):

They (we) used a slightly different method – we calculated the slope of the timeseries and then plotted histograms of the slopes. Note that there is a lot of variability with some real declines and real increases, but the overall trend across populations is strongly centered on (i.e. averages on) about zero (neither up nor down). In fact the title of that paper is “A balance of winners and losers in the Anthropocene” and finds that 85% of the populations didn’t show a trend significantly differently from zero, 8% significantly increased, and 7% significantly decreased. A lot of churn of which species are up or down, but NOT an across the board catastrophic decline. Maybe this is because Outhwaite and Dornelas didn’t study vertebrates? Unlikely. Dornelas et al did pull out different taxa and found that reptiles, amphibians and mammals skewed to more increases than decreases and no real difference from zero in birds and fish (their Figure 4). Or check out Leung et al who analyzed a subset of the LPI data (hence all vertebrates) focusing on the well sampled North American and European regions using a different methodology who got more groups increasing than declining. Or check out Daskalova et al who also found winners and losers were balanced (and most species were neutral). Even the most extreme result of the studies that exclusively use longer term data to look at this question that I am aware of (van Klink et al) shows a 35% decline over 45 years for terrestrial insects and 60% increase over the same period in aquatic insects. I think it is an interesting and challenging question why these studies received little press (despite also being published in high profile journals), but the LPI gets enormous coverage every time it comes out.

These 5 other studies more closely match my childhood memories. There could be weaker trends (+ or – 10 or 20%). And for sure I could be seeing different species (winners replacing lowers). But these 5 studies completely contradict the LPI result (all 5 find a robust mix of increases and decreases and most find something like a balance between increases and decreases). So what is going on?

For one thing, I think the LPI bites off too much – it tries to reduce the state of vertebrates across continents and species to a single number (aka index). That has to sweep a lot of complexity under the rug! There is underlying variability in the LPI too – they just don’t emphasize it as that is not their point. And to a large extent these other papers are just unpacking that complexity by exposing the underlying high variability in trends.

But those other papers find a more neutral balance while the LPI most definitely does not. Something more has to be going on. It could be their data (but some of the aforementioned papers used the same or a subset of the data). Or it could be their methodology (but some of the aforementioned papers used similar methodologies). Personally, I think it is a complex interaction between the data they are putting in and the weaknesses of the methodology (in the sense that every methodology has weaknesses, not that their methodology is fundamentally flawed or wrong). There may be more to say about this in the future. But for now, I hope we can at least pause and think and do a sanity check.

I want to leave no doubt that I am convinced humans are hammering the planet and the vertebrates (and invertebrates and plants) that live on it. We’re removing >50% of the [terrestrial] primary production each year, have removed more than 50% of the tree biomass, modified >50% of the land, use more than 50% of the freshwater, have doubled the amount of nitrogen entering the biosphere each year and nearly doubled the amount of CO2 in the atmosphere since pre-industrial times. But I also don’t think it is possible for there to be a 68% decline in 46 years leading to a projection of a 90% decline over 56 years (10 years from now) nor does a 20% decline in the last two years seem possible. The consequences of 68-90% gone is just too large not to be observed anecdotally and through indirect effects. And the 68-90% decline story just doesn’t align with other major, comprehensive, 1000s of datasets analyses of this question.

What I believe the data show is we’re creating winners and losers – some really big winners and some really big losers and a lot in between, and that’s bad – humans ARE massively modifying the planet in ways that all but the most biodiversity-hating people care about, and the extinctions we are causing are irreversible,so please don’t cite this blog as evidence that “everything is OK”. Its not. Is there room for an “in between”  (bad but not catastrophe) message?

But either way, please think twice before reporting that vertebrates are disappearing from the planet at these incredible rates. Because the logical conclusion is that nothing will be left in a very short time (decade or two) and that doesn’t pass the common sense test. This is not an “all scientists agree” scenario. I personally think the balance of evidence  (such as cited above) points pretty strongly against the LPI conclusion. I worry how many more years scientists (and reporters) can report catastrophic trendlines that predict little to no life of any sort on the planet within our lifetimes and not have people notice that this isn’t actually happening.

 

Note: I am indebted to many colleagues who have talked about this topic with me over the years, some of them co-authors on the paper cited here, some of them co-authors on forthcoming papers, some of them not co-authors, but I want to stress that the opinions here are controversial and my own so I am not listing them here.

 

* The report averaged rates of decline in populations, not total decline in number of individuals (unlike this catastrophic headline). But shouldn’t they be the same thing? Well yes if there were the same number of individuals in each population and each species then a 68% decline of 100 here (to 32) and a 68% decline of 100 there (to 32) would still result in a 68% decline (from 200 to 64). But we know in fact number of individual varies wildly (100x-1000x) across populations and species. So It would be a 68% of 1000 to 320 and a 68% decline of 10 to 3.2 giving 1010 to 323.2 which is STILL 68%. But now the fact the 68% is an average comes in. What if the 1000 declined by 60% to 400 and the 10 declined by 76% to 2.4 or 1010 to 402.4. That’s not a 68% decline but a 60.2% decline even though average the rates 60% and 76% still give an average 68% decline. We don’t know for sure whether large populations are more likely to decline or small populations are more likely to decline, but we do know that at least in birds abundant species are declining while rare species are increasing, so if you assume that it would mean things are actually even worse than the 68% decline in terms of total number of vertebrate individuals increasing, but we don’t know for sure. But I don’t think this is the central reason why the LPI numbers don’t match my childhood memories, nor other studies. With such large data and no truly strong correlations between abundance and decline, most of this comes out in the wash. So theoretically this could be a mathematical reason the total number of individuals has decreased by less than 68% even when the average decline across all populations is 68%. But I don’t think it likely. In fact I think in a weird way, arguing this is a way of distancing the LPI from what it is really claiming/implying.

Ecologists discussing science of coronavirus pandemic – open thread

I don’t know about you but as an ecologist, I am not an expert in disease dynamics nor part of the inner community rapidly exchanging ideas and data. But as an ecologist I have a better handle on notions of population growth, species interactions, individual encounter rates, etc than the average population (and probably the average scientist) and I have felt in a frustrating vacuum of information.

To address this, we’re trying something new here at Dynamic Ecology – an open thread, the main purpose of which is to have a place for the community to have a conversation. Our comments sections have long been the most interesting part of the blog, so now we’re creating a direct path to comments without your having to read 1000s of words of bloviation from me!

First, a few thoughts to give some common terminology/framing to the questions. I think ecologists all know about the power of exponential growth (although this is new and still poorly grasped to most of the world). R0 is the discrete growth rate with no immunity (naive population) and no efforts at social distancing. Best estimates I have seen for Covid 19 is about R0=2.5 which is a good bit higher than flu (and a good bit lower than measles). It seems to be becoming clearer that R0 is as high as it is because people can be infectious before they show symptoms (or even if they never show symptoms like children). Once immunities start to build up or quarantine/social distancing measures start to be put in place a lower growth rate Re (effective growth rate) is observed.  So as far as I can tell there are three strategies.

  1. Squeeze it – extreme social distancing to reduce Re<1. This seems to be what China as well as Japan and South Korea are doing (probably not coincidentally all Asian countries that got hit most by SARS and MERS).
  2. Let it burn – do nothing to lower Re=2.5. Sadly many (all?) countries started down this road – with exponential growth the speed of reaction required seems to be faster than governments can handle.
  3. Stretch it – social distancing to get Re~1.2 (nb 1.2 is an example, not a carefully calculated number, just a wild guess proxy as it is about what influenza does) so that the case load does not exceed hospital capacity. This is what everybody is talking about as “flattening the curve”.

With the stretch it and let it burn strategies the number of people who get sick and then have immunity rises to about 1-1/R0 or about 60% of the population (assuming getting sick once confers immunity – assumed right now but a few counter examples are out there). Then the effective growth rate Re drops below 1 and “herd immunity kicks in”. Individuals can still get sick but it can’t become a self-sustaining epidemic. The primary difference between let it burn and stretch it is the rate at which people get sick which is inversely correlated with how long the epidemic lasts.

I’ve posed several questions below to get this started. I’m not an expert. So the answers to some of these may be obvious in which case, I’d love to know the answer. But I have not seen the answers to any of these despite voracious reading. If they’re not so obvious I expect we could all learn from discussing them.

If you want to respond to a question stay in the same thread (even if the nesting stops at 3 levels). If you want to pose a new question, start a new thread. This is NOT a place for politics, so anything stronger than “many governments have been incompetent at X” (e.g. naming specific individuals, blaming one party or another, or getting distracted off science) will be deleted.

Nominate somebody for International Biogeography Society Awards!

As has been pointed out on this blog before, it does matter who we recognize for society awards. And one of the strongest filters on that is who is nominated. Award committees can’t give an award to somebody who isn’t nominated. It does take a little time and effort to nominate somebody, but not a lot (comparable to writing a letter of reference).

The International Biogeography Society gives out awards at its biennial conference. There is an Alfred Russell Wallace award for lifetime achievement and the MacArthur & Wilson award which targets “relatively early career” (<12 years from PhD).

You can find details on the awards and how to nominate somebody at: https://www.biogeography.org/news/news/2019-call-for-awards/

The deadline is November 29th to nominate somebody for the awards given at the next IBS meeting in Vancouver January 2021 (put it on your calendar to attend too!).

So what are you waiting for? Nominate a deserving biogeographer.

Did North America really lose 3 billion birds? What does it mean?

The journal Science released an article entitled “Decline of the North American avifauna” by Rosenberg et al today (Sep 19, 2019), and already disaster laden headlines are appearing in major newspapers (I’m not going to bother to link to them because they’ll probably change by tomorrow but I bet you’ve already seen this in your favorite news source).

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Statistical Balkanization – is it a problem?

Aside from the question about what statistical methods are appropriate to use in ecology, there is a mostly independent question about how many statistical methods is optimal for use across the field of ecology. That optimum might be driven by how many techniques we could reasonably expect people to be taught in grad school and to rigorously evaluate during peer review. Beyond that limit, the marginal benefits of a more perfect statistical technique could easily be outweighed by the fact only a very small fraction of the audience could read or critique the method. To the extent we exceed that optimum and are using too many different methods, I think it is fair to talk about statistical Balkanization. Balkanization is of course a reference to the Balkans (the region in the former Yugoslavia) and how the increasing splintering into smaller geographic, linguistic and cultural groups became unsustainable and led to multiple wars. I think there is a pretty clear case that too many statistical methods in use is bad for ecology and thus the label of that state as Balkanization is fair (I’ll make that case below). I am less sure if we are there yet or not.

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How badly do authors want open access? What priorities do authors really have? Bringing data to the discussion

If you believe the press, scientists are desperate to publish open access. Is this really true? Turning our scientific method onto ourselves and our peers, let’s see what kind of actual data there is. Every 3 years Ithaka SR (a consulting firm for non-profits) publishes a survey of US faculty for attitudes and behaviors that can help university libraries serve their faculty (https://sr.ithaka.org/publications/2018-us-faculty-survey/). The whole survey is well worth a read. There are interesting questions about social media, data storage, attitudes towards books, etc. But I want to home on their Figure 31 which summarizes data about what kind of journals faculty want to publish in.

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Does the media seize on cases where humans benefit nature?

The single biggest fact about human impact on nature is that it is highly variable. We’re net cutting down forests in the tropics. But we are net increasing forest cover in eastern North America. Farmland birds are in decline in the US and Europe, but that is because farmland – a fairly intense human land use – is decreasing in area in those countries. Eutrophication is harmful to many organisms, but helpful to some. Local biodiversity is trending down in some places but trending up in others. In North America beaver and turkeys, after having been completely eliminated from most of their ranges, have made amazing recoveries trending towards near pre-European levels. Regional diversity, especially in plants, is often increased due to invasive species. Island diversity in birds is often flat or down.

None of those statements contradict the fact that humans are massively changing nature, in many ways for the worse. We have half the tree biomass today compared to what existed pre-human. We appropriate half the fresh water and terrestrial NPP annually. Extinction rates are elevated significantly. We have doubled the rate nitrogen is being introduced to the biosphere. Deer are above pre-European levels in the eastern US with devastating impacts on the structure of forests. Scientists have gotten very good about communicating these negative impacts and maybe have even evolved to a symbiotic relationship with much of the press in communicating this (media loves a disaster whether environmental or human).

But what do we as ecologists do about those facts that can be seen as positive impacts listed in the first paragraph? Continue reading

Bold opinion pieces, RIP?

A few weeks ago, I lamented the passing of papers like Janzen’s Why mountain passes are higher in the tropics (1969) or Janzen’s Herbivore and richness hypothesis (1970) (the Janzen half of Janzen & Connell hypothesis) or the Hairston, Smith & Slobodkin (HSS 1960) paper best known as “why is the world green” even though that is not really the title. These papers were highly speculative, waved a little bit of data around, but mostly put out a hypothesis that attracted researchers for decades. But you don’t really see these kinds of papers any more. Hence my question of whether we should assume this category of paper has come to rest in peace (RIP) (i.e. are dead). Continue reading

How pragmatism resolved the age old battle between rationalism and empiricism (or what is the scientific method?)

If you want to simplify philosophy of science down to the point of gross oversimplification, it has been a millenia long debate between rationalism and empiricism. Although both could be found among the classic Greeks, rationalism was dominate from the time of the Greeks to the Renaissance (almost 2000 years). Rationalism holds that knowledge comes from logical thought. Think Euclid who established the axioms/proofs style of geometry. Or Plato’s cave which emphasized that our senses are crude and misleading (observing mere shadows on the cave wall) in capturing the underlying true essence (the perfect objects outside the cave creating the shadows which we cannot see). Empiricism on the other hand believes that knowledge comes from our sensory experiences of the world outside our mind and mistrusts the mind. Empiricism and rationalism are endpoints of epistemology (the philosophy of how we know things). But they have also been major motivators for scientists framing how to do science.

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ESA seeks input on gold OA, Plan S and the future of publishing

The President of the Ecological Society of America has written a nice blog post on the ESA website about the changing nature of publishing (and how this influences societies and their finances). The short answer is it has big impacts!

As I wrote a few weeks ago, a potentially new seismic shift is happening due to Plan S which seeks to go for pure Gold OA (100% OA journals) and eliminate hybrid OA, green (post a PDF on your website) OA, and other models like JSTOR and old fashioned subscription based models.

ESA is on top of this change and is seeking your input. Read the whole blog post for lots of good thoughts. But if you are tight for time, I have excerpted their request for input:

We are of course very interested in what our members think about this complex issue! Are you currently limited in your ability to access the literature – especially recent papers – and would you be in favor of a rapid shift to open access for ecological research publications? If you are active in submitting and publishing research papers – do you normally have the financial resources to cover the costs of article processing for fully open access journals? Do you have ideas about how to subsidize or afford the publication of papers in these OA journals from authors who cannot afford the processing charges?

ESA will assuredly be affected by continued evolution of the business model for scientific publishing. In order to understand the impact on our members’ professional lives, and not just on our revenues, it is important that we hear from you. I look forward to reading your thoughts. Email (esahq@esa.org), and use “publications” in the subject line. We will keep our members fully informed as Plan S and related developments move forward.