Ice Age? No. Abrupt warmings and hunting together polished off Holarctic megafauna

24 07 2015
Oh shit oh shit oh shit ...

Oh shit oh shit oh shit …

Did ice ages cause the Pleistocene megafauna to go extinct? Contrary to popular opinion, no, they didn’t. But climate change did have something to do with them, only it was global warming events instead.

Just out today in Science, our long-time-coming (9 years in total if you count the time from the original idea to today) paper ‘Abrupt warmings drove Late Pleistocene Holarctic megafaunal turnover‘ led by Alan Cooper of the Australian Centre for Ancient DNA and Chris Turney of the UNSW Climate Change Research Centre demonstrates for the first time that abrupt warming periods over the last 60,000 years were at least partially responsible for the collapse of the megafauna in Eurasia and North America.

You might recall that I’ve been a bit sceptical of claims that climate changes had much to do with megafauna extinctions during the Late Pleistocene and early Holocene, mainly because of the overwhelming evidence that humans had a big part to play in their demise (surprise, surprise). What I’ve rejected though isn’t so much that climate had nothing to do with the extinctions; rather, I took issue with claims that climate change was the dominant driver. I’ve also had problems with blanket claims that it was ‘always this’ or ‘always that’, when the complexity of biogeography and community dynamics means that it was most assuredly more complicated than most people think.

I’m happy to say that our latest paper indeed demonstrates the complexity of megafauna extinctions, and that it took a heap of fairly complex datasets and analyses to demonstrate. Not only were the data varied – the combination of scientists involved was just as eclectic, with ancient DNA specialists, palaeo-climatologists and ecological modellers (including yours truly) assembled to make sense of the complicated story that the data ultimately revealed. Read the rest of this entry »





Statistical explainer: average temperature increases can be deceiving

12 05 2015

Beating-the-Heat-Without-PowerOver the years I’ve used a simple graphic from the IPCC 2007 Report to explain to people without a strong background in statistics just why average temperature increases can be deceiving. If you’re not well-versed in probability theory (i.e., most people), it’s perhaps understandable why so few of us appear to be up-in-arms about climate change. I posit that if people had a better appreciation of mathematics, there would be far less inertia in dealing with the problem.

Instead of using the same image, I’ve done up a few basic graphs that explain the concept of why average increases in temperature can be deceiving; in other words, I explain why focussing on the ‘average’ projected increases will not enable you to appreciate the most dangerous aspects of a disrupted climate – the frequency of extreme events. Please forgive me if you find this little explainer too basic – if you have a modicum of probability theory tucked away in your educational past, then this will be of little insight. However, you may wish to use these graphs to explain the problem to others who are less up-to-speed than you.

Let’s take, for example, all the maximum daily temperature data from a single location compiled over the last 100 years. We’ll assume for the moment that there has been no upward trend in the data over this time. If you plot the frequency of these temperatures in, say, 2-degree bins over those 100 years, you might get something like this:

ClimateVarFig0.1

This is simply an illustration, but here the long-term annual average temperature is 25 degrees Celsius, and the standard deviation is 5 degrees. In other words, over those 100 years, the average daily maximum temperature is 25 degrees, but there were a few days when the maximum was < 10 degrees, and a few others where it was > 40 degrees. This could represent a lot of different places in the world.

We can now fit what’s known as a ‘probability density function’ to this histogram to obtain a curve of expected probability of any temperature within that range:

ClimateVarFig0.2

If you’ve got some background in statistics, then you’ll know that this is simply a normal (Gaussian) distribution. With this density function, we can now calculate the probability of any particular day’s maximum temperature being above or below any particular threshold we choose. In the case of the mean (25 degrees), we know that exactly half (p = 0.50) of the days will have a maximum temperature below it, and exactly half above it. In other words, this is simply the area under the density function itself (the total area under the entire curve = 1). Read the rest of this entry »





InvaCost – estimating the economic damage of invasive insects

7 11 2014

insectinvasionThis is a blosh (rehash of someone else’s blog post) of Franck Courchamp‘s posts on an exciting new initiative of which I am excited to be a part. Incidentally, Franck’s spending the week here in Adelaide.

Don’t forgot to vote for the project to receive 50 000 € public-communication grant!

Climate change will make winters milder and habitats climatically more suitable year-round for cold-blooded animals like insects, but there are many questions remaining regarding whether such insects will be able to invade other regions as the climate shifts. There are many nasty bugs out there.

For example, the Asian predatory wasp is an invasive hornet in Europe that butchers pollinating insects, especially bees, thereby affecting the production of many wild and cultivated plants. I hope that we all remember what Einstein said about pollinators:

If bees were to disappear, humans will disappear within a few years.

(we all should remember that because it’s one of the few things he said that most of us understood). The highly invasive red fire ant is feared for its impacts on biodiversity, agriculture and cattle breeding, and the thousands of anaphylactic shocks inflicted to people by painful stings every year (with hundreds of deaths). Between the USA and Australia, over US$10 billion is spent yearly on the control of this insect alone. Tiger mosquitoes are vectors of pathogens that cause dengue fever, chikungunya virus and of about 30 other viruses. We could go on.

Most of these nasty creatures are now unable to colonise northern regions of Europe or America, or southern regions of Australia, for example, because they cannot survive cold temperatures. But how will this change? Where, when and which species will invade with rising temperatures? What will be the costs in terms of species loss? In terms of agricultural or forestry loss? In terms of diseases to cattle, domestic animals and humans? What will be the death toll if insects that are vectors of malaria can establish in new, highly populated areas?

We’ve proposed to study these and others from a list of 20 of the worst invasive insect species worldwide, and we got selected (i.e., financed!) by the Fondation BNP Paribas. In addition, the Fondation BNP Paribas has selected five scientific programmes on climate change and will give 50,000 € (that’s US$62,000) to the one selected by the public, for a communication project on their scientific programme. This is why we need you to vote for our project: InvaCost. Read the rest of this entry »





Eye on the taiga

24 03 2014

boreal damageDun! Dun, dun, dun! Dun, dun, dun! Dun, dun, daaaaah!

I’ve waited nearly two years to do that, with possibly our best title yet for a peer-reviewed paper: Eye on the taiga: removing global policy impediments to safeguard the boreal forest (recently published online in Conservation Letters).

Of course, the paper has nothing to do with cheesy Eighties music, underdog boxers or even tigers, but it does highlight an important oversight in world carbon politics. The boreal forest (also known as taiga from the Russian) spans much of the land mass of the Northern Hemisphere and represents approximately one quarter of the entire planet’s forests. As a result, this massive forest contains more than 35% of all terrestrially bound carbon (below and above ground). One doesn’t require much more information to come to the conclusion that this massive second lung of the planet (considering the Amazon the first lung) is a vital component of the world’s carbon cycle, and temperate biodiversity.

The boreal forest has been largely expanding since the retreat of the glaciers following the Last Glacial Maximum about 20,000 years ago, which means that its slow progression northward has produced a net carbon sink (i.e., it takes up more atmospheric carbon that it releases from decomposition). However, recent evidence suggests that due to a combination of increased deforestation, fire from both human encroachment and climate change, mass outbreaks of tree-killing insects and permafrost melting, the boreal forest is tipping towards becoming a net carbon source (i.e., emitting more carbon into the atmosphere than it takes up from photosynthesis). This is not a good thing for the world’s carbon cycle, because it means yet another positive feedback that will exacerbate the rapid warming of the planet. Read the rest of this entry »





Shrinking global range projected for the world’s largest fish

7 08 2013
© W. Osborn (AIMS)

© W. Osborn (AIMS)

My recently finished PhD student, Ana Sequeira, has not only just had a superb paper just accepted in Global Change Biology, she’s recently been offered (and accepted) a postdoctoral position based at the University of Western Australia‘s Oceans Institute (in partnership with AIMS and CSIRO). As any supervisor, I’m certainly pleased when a student completes her PhD, but my pride as an academic papa truly soars when she gets her first job. Well done, Ana. This post by Ana is about her latest paper.

Following our previous whale shark work (see herehereherehere, here, here and here), especially the recent review where we inferred global connectivity and suggest possible pathways for their migration, we have now gone a step further and modelled the habitat suitability for the species at at global scale. This paper sets a nice scene regarding current habitat suitability, which also demonstrates the potential connectivity pathways we hypothesised previously. But the paper goes much further; we extend our predictions to a future scenario for 2070 when water temperatures are expected to increase on average by 2 °C.

Sequeira et al_GCB_Figure 3

Global predictions of current seasonal habitat suitability for whale sharks. Black triangles indicate known aggregation locations. Solid line delineates areas where habitat suitability > 0.1 was predicted.

Regarding the current range of whale sharks (i.e., its currently suitable habitat), we already know that whale sharks span latitudes between about 35 º North to South. We also know that this geographical range has been exceeded on several occasions. What we did not know was whether conditions were suitable enough for whale sharks to cross from the Indian Ocean to the Atlantic Ocean – in other words, whether they could travel between ocean basins south of South Africa. Our global model results demonstrate that suitable habitat in this region does exist at least during the summer, thus supporting our hypotheses regarding global connectivity!

It’s true that the extensive dataset we used (30 years’ worth of whale shark sightings collected by tuna purse seiners in the three major oceans – data provided by the IRD, IOTC and SPC) has many caveats (as do all opportunistically collected data), but we went to great trouble to deal with them in this paper (you can request a copy here or access it directly here). And the overall result: the current global habitat suitability for whale sharks does agree well with current locations of whale shark occurrence, with the exception of the Eastern Pacific for where we did not have enough data to validate. Read the rest of this entry »





A carbon economy can help save our species too

20 05 2013

money treeWe sent out this media release the other day, but it had pretty poor pick-up (are people sick of the carbon price wars?). Anyway, I thought it prudent to reprint here on CB.com.

Will Australia’s biodiversity benefit from the new carbon economy designed to reduce greenhouse gas emissions? Or will bio-‘perversities’ win the day?

“Cautious optimism” was the conclusion of Professor Corey Bradshaw, Director of Ecological Modelling at the University of Adelaide’s Environment Institute. He is lead author of a new paper published in the journal of Biological Conservation which reviewed the likely consequences of a carbon economy on conservation of Australian biodiversity.

“In most circumstances these two very important goals for Australia’s future – greenhouse gas emissions reduction and biodiversity conservation – are not mutually exclusive and could even boost each other,” Professor Bradshaw says.

“There are, however, many potential negative biodiversity outcomes if land management is not done with biodiversity in mind from the outset.”

The paper was contributed to by 30 Australian scientists from different backgrounds. They reviewed six areas where Australia’s Carbon Farming Initiative could have the greatest impact on biodiversity: environmental plantings; policies and practices to deal with native regrowth; fire management; agricultural practices; and feral animal control.

“The largest biodiversity ‘bang for our buck’ is likely to come from tree plantings,” says Professor Bradshaw. “But there are some potential and frightening ‘bioperversities’ as well. For example, we need to be careful not to plant just the fastest-growing, simplest and non-native species only to ‘farm’ carbon.

“Carbon plantings will only have real biodiversity value if they comprise appropriate native tree species and provide suitable habitats and resources for valued fauna. Such plantings could however risk severely altering local hydrology and reducing water availability.”

Professor Bradshaw says carefully managing regrowth of once-cleared areas could also produce a large carbon-sequestration and biodiversity benefit simultaneously. And carbon price-based modifications to agriculture that would benefit biodiversity included reductions in tillage frequency, livestock densities and fertiliser use, and retention and regeneration of native shrubs. Read the rest of this entry »





Brave new green world: biodiversity’s response to Australia’s carbon economy

12 03 2013

carbon farming 2I’ve had a busy weekend entertaining visiting colleagues and participating in WOMADelaide‘s first-ever ‘The Planet Talks‘. If you haven’t heard of WOMADelaide, you’re truly missing out in one of the best music festivals going (and this is from a decidedly non-festival-going sort). Planet Talks this year was a bit of an experiment after the only partially successful Earth Station festival held last year (it was well-attended, but apparently wasn’t as financially successful as they had hoped). So this year they mixed a bit of science with a bit of music – hence ‘Planet Talks’. Paul Ehrlich was one of the star attractions, and I had the honour of going onstage with him yesterday to discuss a little bit about human population growth and sustainability. It was also great to see Robyn Williams again. All the Talks were packed out – indeed, I was surprised they were so popular, especially in the 39-degree heat. Rob Brookman, WOMADelaide’s founder and principal organiser, told me afterward that they’d definitely be doing it again.

But my post really isn’t about WOMADelaide or The Planet Talks (even though I got the bonus of meeting one of my favourite latin bands, Novalima, creators of one of my favourite songs). It’s instead about a paper I heralded last year that’s finally been accepted.

In early 2012 at the Terrestrial Ecosystem Research Network (TERN) symposium in Adelaide, the Australian Centre for Ecological Analysis and Synthesis (ACEAS) put on what they called the ‘Grand Challenges’ workshop. I really didn’t get the joke at the time, but apparently the ‘grand challenge’ was locking 30 scientists with completely different backgrounds in a room for two days to see if they could do anything other than argue and bullshit. Well, we rose to that challenge and produced something that I think is rather useful.

I therefore proudly introduce the paper entitled Brave new green world: consequences of a carbon economy for the conservation of Australian biodiversity just accepted in Biological Conservation. The online version isn’t quite ready yet (should be in the next few weeks), but you are welcome to request a preprint from me now. If you attended (the surprisingly excellent) TERN symposium in Canberra last month, you might have seen me give a brief synopsis of our results.

The paper is a rather  in-depth review of how we, 30 fire, animal, plant, soil, landscape, agricultural and freshwater biologists, believe Australia’s new carbon-influenced economy (i.e., carbon price) will impact the country’s biodiversity. Read the rest of this entry »








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