Could tropical species be intensively vulnerable to global warming?

On 12 January 2002, Cambridge University doctoral student Justin Welbergen was studying the behavior of a large colony of flying foxes in subtropical eastern Australia.  What he witnessed that day shocked him.

Doesn't like the heat... a grey-headed flying fox.

Doesn't like the heat... a grey-headed flying fox.

It was a hot afternoon, and as the thermostat climbed above 40 degrees Centigrade, the giant bats became obviously distressed.  They began fighting over shady spots in the canopy.  Then they began licking their wrists and flapping their wings in a desperate effort to cool themselves.  

Finally, as the temperature hit 42 degrees C, they began to die -- in the thousands.  On that day at least 3,500 bats died, in nine different nearby colonies.  Females and juveniles were especially vulnerable.

What Welbergen observed was a phenomenon that has now been seen elsewhere -- from mass disappearances of lizards in Mexico to the dramatic population collapse of the white lemuroid possum in north Queensland rainforests.

Possum in peril... the white lemuroid ringtail  (photo (c) Michael Trenerry)

Possum in peril... the white lemuroid ringtail (photo (c) Michael Trenerry)

There are two striking conclusions from these observations.  First, to the surprise of many, tropical species may be the most vulnerable of all organisms on the planet to global warming.  Second, it isn't a steadily rising thermostat that endangers most species, but short, intense pulses of unusually warm conditions -- heat waves.

Why are tropical species so vulnerable?  In short, many are thermal specialists.  Think, for instance, about a polar bear -- our traditional icon for global warming.  It has to deal with temperatures ranging from, say, minus 50 degrees C in winter to plus 35 degrees C in summer -- a huge range of temperatures.

But tropical species are different.  Lowland tropical species, for instance, might see temperatures ranging from just 25 to 35 degrees during the course of a normal year -- a far narrower range.  As a result, they can become much more thermally specialized.

Where temperatures vary the most in the tropics is as a function of elevation.  On average, for every thousand meters that one goes up in elevation, the temperature drops by 6 degrees C.  

What that means is that tropical species are not just thermal specialists, they also tend to be elevational specialists.  Species tend to be adapted for the very warm lowlands, or for the cooler mid-elevations, or for the wet, cloudy high elevations, where conditions are almost chilly.

And it's the high-elevation specialists -- such as the white lemuroid possum -- that a lot of scientists are really worried about.   

Many tend to be locally endemic species, because their populations are genetically isolated from other populations on different mountaintops.  Hence, they have small geographic ranges and, often, small population sizes.

And they may be intensely vulnerable to global warming.  As temperatures rise, the geographic ranges of many high-elevation species in the tropics are predicted to shrink and fragment -- potentially disappearing altogether.  For instance, in the Australian wet tropics, most upland-endemic species of mammals, birds, reptiles, and amphibians are predicted to disappear entirely if temperatures should rise by more than 4-6 degrees C.

It's a frightening prospect, and it suggests that global warming could have far wider-reaching impacts than many might suspect -- especially in the tropics, the world's biologically richest real estate.

ALERT member Pierre-Michel Forget has just given a wonderful 30-minute interview on this topic.  Forget is a highly authoritative scientist -- a former president of the Association for Tropical Biology and Conservation and now Vice-President of the Society for Tropical Ecology.  He asks, what would just a 1 degree C increase in temperature do to tropical forests and their species?

It's definitely worth a half-hour to hear this enlightening lecture -- and to share it with your colleagues and students. 

The bottom line is this: Given that tropical ecosystems are so rich in species and thermal specialists, the best icon for global warming might not be a polar bear -- but a tropical white possum or flying fox.

 

Will mining company save or destroy the species named after it?

ALERT member Gopalasamy Reuben Clements tell us about a conservation drama playing out in Malaysia. 

In Southeast Asia, the mining of limestone karst -- rugged mountains or pinnacles of limestone that are the remnants of ancient coral reefs -- is big business. 

In fact, the entire construction industry would grind to a halt if it wasn’t for a valuable commodity from karsts -- the limestone needed for cement.

Apart from being important sources of groundwater, limestone karsts are also key habitats for certain plant and animal groups that, in turn, provide important ecosystem services for humanity.

In particular, the nectar-feeding Dawn Bat, which is the principal pollinator for fruit-producing durian trees, require limestone caves to roost in.

As limestone karsts disappear across Southeast Asia, so will the bats, and the durian fruits along with them.

The famous durian fruit, much prized in Southeast Asia  (photo from www.molluscan.com)

The famous durian fruit, much prized in Southeast Asia (photo from www.molluscan.com)

In Peninsular Malaysia, more than 500 limestone karsts are scattered across the landscape.  Because of their isolation from one another for millions of years, limestone hills only a few kilometers apart can host unique species found nowhere else on Earth.

 It's no wonder that these rugged geological formations are regarded as arks of biodiversity.

A limestone karst  (photo by Gopalasamy Reuben Clements)

A limestone karst (photo by Gopalasamy Reuben Clements)

From one such limestone karst in the state of Perak, Malaysia, I discovered a bizarre snail species in 2008.  This snail, Opisthostoma vermiculum, is now the only land snail in the world with four axes of coiling.  It was also considered to be one of the top 10 species discovered in 2008.

Within the same state in Malaysia, scientists recently discovered a new snail species on another limestone karst, known as Kanthan Hill, that is currently being mined.  Aesthetically, the shell of this new species makes less of a statement than O. verimiculum, but it is making a huge statement in conservation circles.

The newly discovered Lafarge snail  (from  Vermeulen & Marzuki (2014)    Basteria  78: 31-34)

The newly discovered Lafarge snail (from Vermeulen & Marzuki (2014) Basteria 78: 31-34)

The scientists who discovered this snail named it Charopa lafargei, after the international mining company Lafarge that owns the mining concession in which this snail was discovered. 

Kanthan limestone hill, home to a number of unique endemic species, including a new snail  (photo by Ong Poh Teck/Basteria).

Kanthan limestone hill, home to a number of unique endemic species, including a new snail (photo by Ong Poh Teck/Basteria).

This endemic snail is already threatened with extinction because of Lafarge’s massive quarry.  It will soon be listed as a Critically Endangered Species. 

Apart from this snail species, Kanthan is also home to nine plant species on Malaysia's Red List of Endangered Plants, one Critically Endangered spider, one gecko, and two other land snails found nowhere else in the world. 

Lafarge has undertaken some initial steps to protect the unique Kanthan wildlife, including a biodiversity assessment.  This is, however, considered insufficient to secure the future of the endangered fauna and flora found there.

Now there are calls for Lafarge to engage leading international biologists to conduct surveys of plants and animals in and around the quarry, leading to habitat and species management recommendations that are publicly available and peer-reviewed.  Till then, quarry expansion should be prohibited.

Beyond this issue, what’s urgently needed is a conservation assessment that ranks limestone karsts in Malaysia according to their suitability for preservation or quarrying.  This national-level exercise should consider the biological, geological, economic and cultural importance of each individual hill. 

Unfortunately, getting funding for this from industry and government has been extremely tough.  But it's an urgent task -- the stakes for some of Southeast Asia's most unique biodiversity could not be higher.

Perils growing for Earth's biodiversity hotspots

Biodiversity hotspots are Earth's most biologically important real estate.  An important new study -- which you can download free here -- sees dark clouds on the horizon for many these crucial ecosystems.

Where the rare things live...

Where the rare things live...

There are 35 biodiversity hotspots across the planet.  They encompass a wide range of different ecosystems but they all have two key features:

First, they're jam-packed with species, especially those that don't occur anywhere else on Earth.  These are known as "locally endemic species" and they're notoriously vulnerable, because they live in just one small area.  For instance, the island of Madagascar has lots of species, such as lemurs, that are completely unique to the island.

Second, hotspots, by definition, have been nuked by land-use change: at least 70% of the original vegetation has disappeared.

The new paper, led by geographer Sean Sloan and including ALERT director Bill Laurance, used a rigorous satellite analysis to estimate how much of the original vegetation survives in an intact condition in each hotspot. 

Unfortunately, most hotspots have much less intact vegetation than previously estimated.  Half now have less than a tenth of their original vegetation -- at which points things start to look seriously dodgy for biodiversity, in part because the original habitat gets severely fragmented and reduced.

An interesting finding is that the hotspots that were formerly in the best shape, in terms of having more of their original vegetation, suffered the worst.  Drier habitats, such as dry forests, open woodlands, and grasslands, fared badly, largely because of expanding agriculture.

These findings highlight an important reality.  For biodiversity, the Earth is far from homogenous, with certain crucial regions overflowing with rare species.  Conserving the last vestiges of these endangered ecosystems is simply vital if we're going to ward off a catastrophic mass-extinction event.

 

Species disappearing "1000 times faster than normal"

Want to know one of the most hotly debated questions in environmental science?  It's this: How fast are species disappearing today?  A new paper in the leading journal Science suggests the answer is -- very fast indeed.

Undiscovered species... this Amazonian jay doesn't even have a scientific name yet (photo by Mario Cohn-Haft)

Undiscovered species... this Amazonian jay doesn't even have a scientific name yet (photo by Mario Cohn-Haft)

The paper, led by ALERT member and Duke University Professor Stuart Pimm with a team of eminent coauthors, makes several key arguments:

- Species extinctions today are occurring roughly 1000 times faster than the 'background' (or natural) rate that prevailed before humans appeared on Earth

- We know where the most imperiled species are located, with particularly big concentrations in the tropical Asia-Pacific region, especially in places like the Philippines, Borneo, and Sumatra

-Other regions with lots of extinction-prone species include the Andes mountains, West Africa, Madagascar, and other scattered pockets of the world

- Millions of species have not yet been discovered (scientifically described or studied) by scientists; for example, huge numbers of plant, insect, fungi, and nematode species are undiscovered, among many others

- Many of the undiscovered species are imperiled because they have small geographic ranges and occur in vulnerable parts of the world -- known as 'biodiversity hotspots' -- that have already lost much of their original habitat

- Protecting the surviving habitats in the biodiversity hotspots is crucial if we are to stave off a dramatic collapse of biodiversity on Earth

For those who care about biodiversity, this paper (which you can download free at the link above) is an authoritative and highly readable summary of what we know, think, and suspect about the future of life on Earth.