Why we simply must have predators

ALERT member John Terborgh is a scientist of enormous stature, whose many accomplishments include a rare MacArthur 'Genius' Award.  Here he tells us why predators are so crucial for the Earth -- a lesson with big implications for understanding nature and our future:

Amur Leopard -- just 70 left in the wild today.

Amur Leopard -- just 70 left in the wild today.

Forty-five years ago, three leading ecologists asked a question of child-like simplicity, “Why is the world green?”

We take a green world for granted, yet this deceptively simple question goes to the very heart of how ecosystems work.

The world is green, the trio argued, because predators limit the numbers of herbivores, thereby protecting plants and allowing them to flourish.

At the time this idea was floated, other ecologists were busy discovering that plants manufacture a potent arsenal of chemical compounds to deter herbivores -- everything from deadly toxins to chemicals that make them hard to digest. 

Far from being helpless, these other ecologists argued, plants actively defend themselves, and this keeps herbivore numbers down.  Under this scenario, predators aren't really needed to keep the world green.  

Who is right?  In theory, it should be simple to find out: just remove the predators from an ecosystem and see what happens. 

Wolves -- widely persecuted but trying to make a comeback in parts of North America and Europe.

Wolves -- widely persecuted but trying to make a comeback in parts of North America and Europe.

But it's one thing to remove little predators such as insects and spiders.  Getting rid of big predators, such as wolves, lions, or jaguars, is a far taller task.  To perform such an experiment properly, one would need to fence off huge areas, some with predators and prey, some with prey alone, and others with neither. 

The cost of such an ambitious experiment would be so high that, to this day, nobody has tried it.  As a result, ecologists are still arguing about why the world is green.

An Accidental Experiment

But purely by accident, an unplanned experiment in Venezuela created the right conditions to test the 'Green World' hypothesis.  There, a massive expanse of forest flooded by a hydroelectric dam created hundreds of artificial islands.  The smallest islands were barely the size of a tennis court; the biggest, at hundreds of hectares, would span a dozen large golf courses.

My students, colleagues, and I studied these islands for 14 years.  And what we found is enormously exciting -- and scary.

The largest islands had enough habitat to support both predators and their prey.  But as island size declined, fewer and fewer species of predator remained.  Once below 10 hectares in size -- equivalent to about 20 football fields -- the predators vanished entirely. 

The Harpy -- king of eagles.

The Harpy -- king of eagles.

At this point you have an ecosystem with a few species of herbivores -- particularly howler monkeys, an iguana, a type of tortoise, and leaf-cutter ants -- but nothing to eat them.

With little to keep herbivores in check, did these islands stay gloriously green, or collapse ecologically?  

Ecological Collapse

What we observed was ecological chaos.  Herbivores attacked foliage in all parts of the forest. The first plants to be killed were seedlings, cut up and carried away by leaf-cutter ants, while howler monkeys and iguanas defoliated trees and vines in the canopy.

Without predators, leaf-cutter ants can decimate a forest.

Without predators, leaf-cutter ants can decimate a forest.

Small saplings were the next to disappear under the herbivore onslaught, followed by larger saplings and woody vines.  Finally, after a decade or more, big canopy trees began to die, standing leafless, ghost-like.

By the end of our study, the once-verdant forest was a degraded tangle of shrubs and vines -- a pathetic vestige of their original diversity.

And while herbivores had won, they ultimately brought about their own self-destruction.  In the end, the decimated islands barely sustained any life at all.

The trio of ecologists -- the architects of the 'Green World' hypothesis -- were right.  We need predators to keep our planet verdant and healthy, and to maintain biodiversity.

Alternative States

The 'alternative state' of a predator-free island is alarming.  Equally worrisome is that we can get there in a variety of ways.  Killing off predators is one way -- and we humans are very good at doing that.

Another way is flooding an ecosystem with nutrients, a process called "eutrophication".  This can happen, for example, if we carelessly use farming fertilizers, which then leach into waterways and other ecosystems.  Biodiversity depends on a balance, and tip that balance too far one way and nutrient-loving species dominate while excluding many other species.

Depressing 'alternative states' can arise for other reasons too, such as disrupting natural fire regimes or introducing exotic species that fundamentally change ecosystems.

But for me, the widespread decimation of predators is the most worrisome way that we are disrupting the natural world.  For that reason, I strongly support efforts to 're-wild' ecosystems -- to reintroduce big carnivores such as wolves, grizzy bears, and tigers to regions where they once held sway.  

Arctic fox in the summer.

Arctic fox in the summer.

Rewilding sizable parts of the world will not be easy.  There are many who will object -- out of fear or ignorance or potential risks to their livelihoods. 

But the world needs predators.  I have been studying nature for a long time, and one thing I have learned is that biodiversity utterly depends on them.

Bringing the science we need to maturity and explaining it to policymakers and the public is a vital goal for our next generation of conservationists.


Unconventional-gas mining: Are we grabbing a tiger by the tail?

In Australia, as elsewhere, huge efforts are being focused on exploiting unconventional-gas deposits.  Australian ecologist professor Steve Turton explains what it's all about and why it should be making us nervous. 

We hear a lot these days about unconventional gas.  What is it? 

Unconventional gas includes coal-seam gas, shale gas, and tight gas.  There's a heck of a lot of it on Earth but it's found in complex geological systems and can be devilishly difficult to extract. 

In its 2013 report, the U.S. Energy Administration estimated that recoverable supplies of shale gas totaled some 188 trillion cubic meters worldwide.  Known reserves occur in 41 different countries. 

And there's a lot of coal-seam gas too -- about 143 trillion cubic meters worldwide, according to a 2006 study.

This sounds like good news for an energy-hungry world, so what's the downside? 

For starters, like many forms of mining, unconventional-gas extraction has been implicated in a suite of nasty environmental impacts.  Some of these were highlighted in an independent report commissioned by the Australian Council of Environmental Deans and Directors, which focuses largely on coal-seam gas exploitation in Australia.

Why worry about coal-seam gas?  For starters, there are major surface impacts, with native vegetation being bulldozed for often-dense networks of roads and drilling platforms.  Fragmentation of forests is a common result, with potentially serious impacts on biodiversity. 

In farming regions, coal-seam gas operations can have large impacts on agriculture and forestry operations.  They can also pollute surface waters and have largely unknown impacts on vital groundwater resources.

Unconventional-gas production often competes with existing land uses, such as agriculture, plantation forestry, and urban areas, leading to heated conflicts among different users.  The Lock the Gate Alliance in Australia resulted from a conflict between farmers and coal-seam gas companies.  Expect wicked environmental problems to arise for irrigated agriculture and intensive grazing as well.

A big problem is getting rid of dirty water.  For coal-seam gas extraction, high-pressure water is pumped into wells to hydraulically crack ("frack") gas-bearing strata, releasing the gas.  The gas is pumped to the surface along with a lot of dirty water, salt, and chemicals liberated by the fracking process. 

Disposing of all this dirty water is a big problem.  Heavy rains can cause containment ponds to overflow, releasing the dirty water into nearby waterways.  

Compared with the surface risks of unconventional-gas extraction, we know much less about how groundwater is affected when mining shale gas and coal-seam gas.  A key worry is this: Could underground aquifers vital for irrigation and human uses be contaminated? 

What is the way forward for unconventional gas?   There is little doubt that production of unconventional gas poses a risk to biodiversity and groundwater.  We also know the industry often encroaches into high-value landscapes, competing with biodiversity conservation, the production of food and fiber, and sometimes even moving into urban or peri-urban areas.

Because the planet needs energy, it's clear that unconventional gas is not going to go away.  Managing its exploration and production will require a holistic landscape approach, taking into account cumulative impacts and strategic assessment frameworks

Where there are key unknowns –- as often occurs when one is dealing with groundwater –- the precautionary principle should be applied.  If we're uncertain about the environmental impacts that might arise, the wisest choice is simply not to drill.

Otherwise the tiger we're desperately trying to hang onto might just turn around and bite us.

 

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.

 

Protected areas do far better when governments work to make them succeed

Why do some protected areas do a good job of protecting their biodiversity whereas others struggle to keep the poachers and illegal loggers out?

Protecting biodiversity takes effort -- but it's worth it  (photo by William Laurance)

Protecting biodiversity takes effort -- but it's worth it (photo by William Laurance)

In a new analysis published in Biological Conservation, ALERT members Corey Bradshaw and Bill Laurance, along with colleague Ian Craigie, argue that it largely comes down to national commitment.

When you factor out national-level variables like population size, socioeconomic differences, and the like, one big conclusion jumps out at you. 

Nations that are serious about protecting their protected areas -- and by that we mean they designate most of their reserves into IUCN categories I-IV, which enjoy the greatest legal protections -- their reserves and biodiversity fare a lot better.

In many nations -- China being an obvious example -- few reserves are fully protected.  Rather, the reserves can also support a range of human uses, such as limited hunting, natural-products harvests, logging, and land clearing.  Such reserves fall into the IUCN categories V and VI.   

However, reserves that are nominally fully protected include things like national parks, World Heritage sites, and wildlife preserves, where conservation of nature is the top priority.

In their analysis, Bradshaw and colleagues tried to factor out all the complicating factors that can bedevil such national-level comparisons.  The result was that the "high-protection" nations did a lot better overall than the "lower-protection" nations in terms of maintaining the biological health of their reserves.

The answer is appealing intuitively and makes sense.  The more you invest in protecting nature reserves -- and that means not only defending the reserves but also striving the limit the threatening land-use changes immediately around them -- the better their biodiversity fares.

Conserving nature is often not cheap.  For that reason, nations that make a real commitment to protecting their imperiled reserves and biota should be recognized and heartily applauded.

 

The next big environmental crisis: Indonesian New Guinea

We had a bit of fun with our 'Drop Bears' blog last week -- which was based on a legitimate scientific paper but was entirely in jest -- but we're being deadly serious now. 

In brief, the Indonesian half of the island of New Guinea -- one of three great remaining tropical wildernesses on Earth -- is under dire assault.  This is an issue that should light up the radar of conservationists throughout the world. 

Rampant oil palm development in Indonesia New Guinea  (photo (c) Ardiles Rante, Greenpeace).

Rampant oil palm development in Indonesia New Guinea (photo (c) Ardiles Rante, Greenpeace).

The other half of the island of New Guinea -- the nation of Papua New Guinea -- has certainly suffered its share of environmental ills, with rampant industrial logging and mining development, severe fires in the highlands, and the notorious SABLs -- Special Agricultural and Business Leases -- that have often been snapped up by foreign logging firms and now span some 11% of the nation's land area.

But the situation in Indonesian New Guinea -- the Provinces of Papua and West Papua -- is, if anything, even worse.  And it is likely to become one of the major rainforest crises of our time.

People in the know say its only a matter of time before environmental chaos descends in Indonesian New Guinea.  First, the government there places little emphasis on the rights of the island's many indigenous communities, who have lived on their traditional lands for millennia.

Second, the Indonesian government has transmigrated millions of Javanese and other Indonesians to New Guinea, displacing traditional peoples and destroying native ecosystems in the process.  This program has been enormously unpopular with native New Guineans.

Third, oil palm is exploding across Indonesia New Guinea.  The Indonesians have a saying, "Sumatra was yesterday, Borneo is today, and New Guinea is tomorrow", reflecting their wildly ambitious plans to expand oil palm, logging, mining, and other developments across the island at the expense of native ecosystems.

Indonesia now has the world's highest absolute rate of forest destruction  (from Mongabay.com).

Indonesia now has the world's highest absolute rate of forest destruction (from Mongabay.com).

And finally, Indonesia President Joko Widodo has just announced a scheme to build a 4,000 kilometer-long 'Trans-Papuan Highway' across Indonesian New Guinea.  This has the potential to open up the island like a flayed fish, exposing it a range of new environmental pressures -- the results of which are often fatal for forests and biodiversity

We've been accustomed to hearing about environmental crises in Borneo, Sumatra, and the Amazon.  Unless the international community can convince the Indonesian government to change its tack, get ready to start hearing a lot more about environmental crises in Indonesian New Guinea too.

 

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.

 

Why biodiversity is declining even as protected areas increase

Why is biodiversity around the world in so much trouble, even though we keep adding new protected areas?  A new paper led by Australian researcher Ro Hill provides a compelling explanation.  Here, Ro summarizes her and her colleagues' key findings:

We’ve expanded the protected area coverage around the globe, to around 15% of the land surface -- with more than a quarter of all countries already exceeding the agreed global target of 17% by 2020.  But biodiversity loss continues apace.

Biodiversity in trouble...

Biodiversity in trouble...

Why?   Our new paper models how this paradox arises in tropical forests, from competition between governance regimes, and makes four important points:

1. The forces that drive forest protection do not necessarily oppose those that drive forest clearance for development. 

The diagram above says it all: we can keep expanding the developed area of the planet AND expanding protected areas as long as there are still some remaining forested habitats.
 
The power of the “develop” and “protect” governance regimes determines the strength of the forces that move the boundaries between areas under protection, areas of remaining forest habitat, and areas under development.

The leaders of the G20 nations recently gave a huge boost to the power of development regimes by promising to invest 60-70 trillion U.S. dollars on new infrastructure projects by the year 2030.  There is no such investment for conservation -- nothing even close!

2.   The power of the “protect” governance regime can actually be lowered as protected areas increase.
 
People may believe that when new protected areas are created, there are more natural areas –- whereas the reality is that every day there are less.  This lowers public concerns about risks from biodiversity loss, decreasing pressure on politicians and weakening the power of the “protect” governance regime.
 
3.  Prioritizing protected area placement by proximity to active agricultural frontiers would make them more effective.

Targets should include both the desired Area under protection AND the absolute limits on Area under development through habitat conversion.

4.  Strengthening the forces that maintain and restore habitat (and oppose its development) is vital to halt biodiversity loss.

This means we must generally favor land-sharing as a conservation strategy rather than land-sparing.  The governance forces that drive land sparing don’t necessarily oppose the governance forces that drive forest clearance for development, so you still get net loss.
 
Hence, strengthening the relative power of land-sharing governance regimes (i.e. those that maintain traditional, sustainable land use, alternative sustainable land use, or restore degraded habitat) is likely, we argue, to have a greater long-term benefit for biodiversity conservation.

Unraveling how governance and power affect biodiversity conservation is a new frontier in conservation science -– but this paper makes an important start and shows where we need to focus our attention.