Savanna birds show surprising vulnerability to climate change

Dr April Reside of James Cook University has just spent several years studying birds that live in Australia's tropical savannas, with an eye to assessing their potential vulnerability to climate change.  You don't have to be a bird-lover to find some of her conclusions alarming.

Cry for help... the Papuan Frogmouth is vulnerable to climate change.

Cry for help... the Papuan Frogmouth is vulnerable to climate change.

When it comes to species being vulnerable to climate change, many people think of polar bears -- or other species that are highly specialized to local conditions.

A lot of research has focused, for example, on mountain-top endemics -- species reliant on cool, misty mountains whose habitat could shrink and collapse with rising temperatures.

Fewer people are thinking about widespread, generalist, common species -- why would they be of concern?

Many birds in the Australian tropical savannas are widespread generalists.  This is probably because they are adapted to highly variable conditions, and need to continually travel about to find the next source of food –- usually flowering trees or pulses of insects after recent rains.

Vast expanses of northern Australia are dominated by tropical savannas.

Vast expanses of northern Australia are dominated by tropical savannas.

Such ephemeral food sources might become increasingly rare or thin on the ground if conditions get tougher with climate change.  So, these widespread generalist species might be more vulnerable to climate change than many have expected.

I investigated the vulnerability of 243 bird species found in Australian tropical savannas to climate change.  To do this I incorporating a range of different factors: their sensitivity to fire, their dietary breadth, their range size, and their abundance.

I also incorporated the amount of suitable climate space each species was likely to have by the year 2085, under a severe climate-change scenario.

The critically endangered Golden-shouldered Parrot is another big worry  (image from Karl Seddon,

The critically endangered Golden-shouldered Parrot is another big worry (image from Karl Seddon,

I found that many savanna species that are restricted to the Cape York Peninsula are particularly vulnerable to climate change.  Alarmingly, this includes endangered Golden-shouldered Parrot and the endangered Buff-breasted Buttonquail.

However, some species that occur across the northern savannas might actually benefit from climate change -- at least if rainfall changes as some projections indicate.

We will have to keep monitoring the species, particularly those that are already declining and likely to be severely impacted by climate change. 

A key strategy is to devise plans of how to intervene if necessary.  To do that, we might have to make tough choices in the future.  For instance, might some species have a better chance of persisting in zoos than in the wild?  Might major changes in burning, grazing, or land-clearing practices -- possibly putting us as odds with powerful agricultural interests -- become necessary?

My in-depth work on savanna birds shows me that we can't worry just about polar bears or specialized moutaintop species.  We also need to fret about lots of other wildlife in which climate change could make their battered and dwindling populations even more vulnerable to severe stresses in the future.


The scariest things about climate change are what we don't know

Some argue that, when it comes to climate change, we should play down our uncertainties -- because climate-change deniers will just seize on those unknowns as an excuse for inaction.

Clinging to survival

Clinging to survival

But in a brief, highly topical essay just published today, TESS director Bill Laurance argues that scientists have to be entirely frank about uncertainty -- and that many of the scariest things about climate change are in fact the things we don't know.

Read the essay here

In just three minutes you can get a sense of what we we know, what we don't know -- and what we don't know we don't know about climate change.


A drier tomorrow? New study predicts less rain across planet

Expect things to get drier.  That's the alarming conclusion of a new study that projects large swaths of the Earth--including the Amazon, Central America, and Indonesia--to have fewer days with rainfall in the future.

No smoking, please.... (photo by Jedediah Brodie)

No smoking, please.... (photo by Jedediah Brodie)

Precipitation is a notoriously difficult thing to predict.  For instance, different global circulation models--supercomputer simulations of future climates--often make wildly varying predictions about future rainfall.

But the new study, which seems surprisingly robust, focuses on how changing climates could affect daily rainfall in the future.  It finds that rainforests and Mediterranean ecosystems could have as many as 30 fewer days of rainfall each year.

In many parts of the world, such changes could lead to major tipping points.  For instance, large expanses of the tropics support rainforests that suffer periodic droughts and are already near their environmental limits.

The big worry is that declining rainfall could interact with rampant land-use change--such as habitat fragmentation, logging, and slash-and-burn farming--to create massive wildfires. 

In the late 1980s, for instance, wildfires scorched millions of hectares of forest in the Amazon and Borneo. 

The one-two punch of drought and human land-use change was fatal for many forests.

Do forests function like 'biotic pumps' for rainfall?

One of the more striking and controversial hypotheses to emerge in the last decade is the notion that intact tracts of forest, stretching from coastal to inland areas, may help to suck oceanic moisture far inland--functioning like a giant 'biotic pump'. 

This idea might sound slightly prosaic, but its potential implications are so profound and its putative mechanism so controversial that it has created fierce divides within the climatology and environmental-science communities.

No forest, no rain?

No forest, no rain?

The biotic-pump idea was first proposed in 2006 by a pair of Russian biophysicists, Anastasia Makareiva and Victor Gorshkov, in a highly theoretical analysis that even mathematicians found daunting.  The controversy has raged ever since then.

Everyone knows that forests (especially rainforests) emit a lot of water vapor, and Makareiva and Gorshkov argued that when this vapor condensed into rain it created a large suction.  That suction pulled cloudy, rain-bearing water from coastal areas inland, they argued, and thereby was crucial for maintaining rainfall in inland areas.  

The really striking implication of the Makareiva -Gorshkov hypothesis is this: If you break up the forest, you lose the suction, and the biotic pump stops working.  This, of course, would be an enormously important implication for forest conservation, if true.  Imagine millions of farmers clamoring for more forest in their region because their crops were drying up!

But the idea remains intensely controversial, because many physicists simply don't buy the idea of condensing water vapor creating a big suction.  For instance, just one website focused on this issue (and there are quite a number) had hundreds of individual comments, many very impassioned in nature.  This only happens in science if a debate is truly volcanic in nature.

This is a debate to keep your eye on--huge implications, and huge controversy about the biotic-pump idea itself.