Climate explained: humans have dealt with plenty of climate variability

23 09 2020
© Professor John Long, Flinders University, Author provided

(originally published on The Conversation)


How much climate variability have humans dealt with since we evolved and since we started settling (Neolithic times)? How important was migration to human survival during these periods?


The climate always fluctuates as variation in the Sun’s heat reaching Earth drives glacial-interglacial cycles. Over the past 420,000 years there have been at least four major transitions between ice ages and relatively warmer interglacial periods.

Modern humans emigrated from Africa to populate the rest of the globe between 120,000 and 80,000 years ago, which means our species has had to adapt to many massive climate transitions.


Warming and cooling

The Last Interglacial 129,000–116,000 years ago was a period of intense global warming (from around 2 ℃ higher than today to as much as 11 ℃ higher in the Arctic), leading to a large reduction of the Arctic, Greenland and Antarctic ice sheets, and a 6–9 m rise in sea level.

The front of a glacier breaking away and falling into the sea.
Arctic glaciers have melted before. Flickr/Kimberly Vardeman, CC BY

The Last Glacial Maximum from 26,500–19,000 years ago coincided with a large drop in atmospheric CO₂ and a 4.3 ℃ cooling globally.

Read more: Climate explained: will the tropics eventually become uninhabitable?


Low temperatures turned much of the world’s water into ice and expanded glaciers.

Read the rest of this entry »

Environmental damage kills children

1 10 2019

Yes, childrenairpollutionit’s a provocative title, I agree. But then again, it’s true.

But I don’t just mean in the most obvious ways. We already have good data showing that lack of access to clean water and sanitation kills children (especially in developing nations), that air pollution is a nasty killer of young children in particular, and now even climate change is starting to take its toll.

These aspects of child health aren’t very controversial, but when we talk about the larger suite of indicators of environmental ‘damage’, such as deforestation rates, species extinctions, and the overall reduction of ecosystem services, the empirical links to human health, and to children in particular, are far rarer.

This is why I’m proud to report the publication today of a paper on which I and team of wonderful collaborators (Sally Otto, Zia Mehrabi, Alicia Annamalay, Sam Heft-Neal, Zach Wagner, and Peter Le Souëf) have worked for several years.

I won’t lie — the path to publishing this paper was long and hard, I think mainly because it traversed so many different disciplines. But we persevered and today published the paper entitled ‘Testing the socioeconomic and environmental determinants of better child-health outcomes in Africa: a cross-sectional study among nations* in the journal BMJ Open.

Read the rest of this entry »

Increasing human population density drives environmental degradation in Africa

26 06 2019



Almost a decade ago, I (co-) wrote a paper examining the socio-economic correlates of gross, national-scale indices of environmental performance among the world’s nations. It turned out to be rather popular, and has so far garnered over 180 citations and been cited in three major policy documents.

In addition to the more pedestrian ranking itself, we also tested which of three main socio-economic indicators best explained variation in the environmental rank — a country’s gross ‘wealth’ indicator (gross national income) turned out to explain the most, and there was no evidence to support a non-linear relationship between environmental performance and per capita wealth (the so-called environmental Kuznets curve).

Well, that was then, and this is now. Something that always bothered me about that bit of research was that in some respects, it probably unfairly disadvantaged certain countries that were in more recent phases of the ‘development’ pathway, such that environmental damage long since done in major development pulses many decades or even centuries prior to today (e.g., in much of Europe) probably meant that certain countries got a bit of an unfair advantage. In fact, the more recently developed nations probably copped a lower ranking simply because their damage was fresher

While I defend the overall conclusions of that paper, my intentions have always been since then to improve on the approach. That desire finally got the better of me, and so I (some might say unwisely) decided to focus on a particular region of the planet where some of the biggest biodiversity crunches will happen over the next few decades — Africa.

Africa is an important region to re-examine these national-scale relationships for many reasons. The first is that it’s really the only place left on the planet where there’s a semi-intact megafauna assemblage. Yes, the great Late Pleistocene megafauna extinction event did hit Africa too, but compared to all other continents, it got through that period relatively unscathed. So now we (still) have elephants, rhinos, giraffes, hippos, etc. It’s a pretty bloody special place from that perspective alone.


Elephants in the Kruger National Park, South Africa (photo: CJA Bradshaw)

Then there’s the sheer size of the continent. Unfortunately, most mercator projections of the Earth show a rather quaint continent nuzzled comfortably in the middle of the map, when in reality, it’s a real whopper. If you don’t believe me, go to and drag any country of interest over the African continent (it turns out that its can more or less fit all of China, Australia, USA, and India within its greater borders).

Third, most countries in Africa (barring a few rare exceptions), are still in the so-called ‘development’ phase, although some are much farther along the economic road than others. For this reason, an African nation-to-nation comparison is probably a lot fairer than comparing, say, Bolivia to Germany, or Mongolia to Canada.

Read the rest of this entry »

First Australians arrived in large groups using complex technologies

18 06 2019


One of the most ancient peopling events of the great diaspora of anatomically modern humans out of Africa more than 50,000 years ago — human arrival in the great continent of Sahul (New Guinea, mainland Australia & Tasmania joined during periods of low sea level) — remains mysterious. The entry routes taken, whether migration was directed or accidental, and just how many people were needed to ensure population viability are shrouded by the mists of time. This prompted us to build stochastic, age-structured human population-dynamics models incorporating hunter-gatherer demographic rates and palaeoecological reconstructions of environmental carrying capacity to predict the founding population necessary to survive the initial peopling of late-Pleistocene Sahul.

As ecological modellers, we are often asked by other scientists to attempt to render the highly complex mechanisms of entire ecosystems tractable for virtual manipulation and hypothesis testing through the inevitable simplification that is ‘a model’. When we work with scientists studying long-since-disappeared ecosystems, the challenges multiply.

Add some multidisciplinary data and concepts into the mix, and the complexity can quickly escalate.

We do have, however, some powerful tools in our modelling toolbox, so as the Modelling Node for the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH), our role is to link disparate fields like palaeontology, archaeology, geochronology, climatology, and genetics together with mathematical ‘glue’ to answer the big questions regarding Australia’s ancient past.

This is how we tackled one of these big questions: just how did the first anatomically modern Homo sapiens make it to the continent and survive?

At that time, Australia was part of the giant continent of Sahul that connected New Guinea, mainland Australia, and Tasmania at times of lower sea level. In fact, throughout most of last ~ 126,000 years (late Pleistocene and much of the Holocene), Sahul was the dominant landmass in the region (see this handy online tool for how the coastline of Sahul changed over this period).

Read the rest of this entry »

South Australia doesn’t value its environment

5 09 2018

how we treat our environmentThe South Australian State Budget was released yesterday, and as has been the trend for the last ten years or so, the numbers are not good for the State’s environment.

While it has been reported that the budget includes the loss of 115 full-time staff from the Department of Environment and Water, the overall cuts run much deeper. They also herald a new era of not giving a tinker’s cuss for the sorry state of our environment.

I took the liberty of amassing the budget data with respect to environmental spending in this State since 2002-2003 (the earliest year I could find budget papers), and now I’ve just added the 2018-2019 data.

If I’ve selected the appropriate amounts, — side note: someone desperately needs to teach these budget bean-counters how to standardise, report, itemise, and organise data much, much better than they do (my first-year students could do a better job drunk and blindfolded) — then this is what environmental spending (including environment, biodiversity, water, and the Environment Protection Authority) has looked like since 2002: Read the rest of this entry »

Death of the question

17 12 2015

Zombie apocalypse

Zombie apocalypse

It’s something I’ve noticed over the years going to scientific conferences and seminars — the number of questions, and more importantly their quality, have declined.

Sure, it’s anecdotal and it might just be that my perspective has changed, but I’d bet my left testicle that it’s true.

But why? There are possibly many contributing factors, such as increasingly jam-packed conferences with multiple concurrent sessions, a massive and increasing number of participants and less time for each of us to present our work. However, I think the main reason is that we’re now all glued to our electronic devices.

Yes, I’m talking about the Twitteratti, but also the tablet-tossers, laptop-layabouts and the iPhone-idiots. We have a saying in our family when we spot a smartphone zombie oblivious to oncoming traffic that she/he looks like a “… spastic fingering a sandwich” (not my quote, but I am particularly fond of using it).

Read the rest of this entry »

Challenging the traditional conference model

28 08 2015

keeping-the-audience-awakeAn interesting take on conference culture by Diogo Veríssimo (mastermind behind I Fucking Love Biodiversity).

Just a few weeks back, more than 2000 conservationists got together in Montpellier, France, for the 27th International Congress on Conservation Biology (ICCB). I have been attending these conferences since 2008, and once again had a blast. Yet as I went through the usual talks, posters, work meetings, and this and that social, I could not help but feel that the traditional conference model was hindering, not helping me, maximise my benefits.

In my experience of conservation conferences, the content is largely delivered via a one-way channel, and attendees listen passively until the chance for a question or two comes up at the end. If time allows, that is, and it rarely does. Given the huge costs (and the footprint) of these events, how can we maximise the outcomes of these meetings?

Let’s look first at what is currently the backbone of most conferences anywhere: the oral presentation. Currently, the gold standard for the vast majority of ICCB presenters is the 15-min presentation, and those who are denied that chance often say they have been “downgraded”. I find this unfortunate.

My biggest criticisms of our current approach to content management during a conference is that it leaves the discussion to happen informally and without the benefit of the collective knowledge that comes together at these meetings. Many conservationists are keen to avoid long-winded lectures in their classrooms, but when we come together, those concerns seem to go out the window. The Q&A after a talk should be the most important part of a session for either the presenter (expert feedback can save a lot of time and resources) and the audience (who otherwise cannot focus on what they think is important).

Giving sessions enough Q&A time, which I argue would have to be as long as the time given to presentations, would imply having fewer presentations — unless we have shorter presentations. The ICCB already has the speed presentation, a format that lasts just 5 minutes. Why not make that the default? Yes, presenting your content effectively in 5 minutes is an acquired skill, but not much different in kind from writing an abstract to a paper. Having presented in both traditional and speed format, I am convinced presentations strongly suffer from the law of diminishing returns, meaning the difference from the audience point of view ends up being small. This is particularly true if fewer talks means more time for the audience to interact and ask about the things in which they are interested, rather than what the presenter thinks they should learn. Read the rest of this entry »