The plight of tropical migratory species

So much remains unknown about the tropics, including the extent to which species living in these environments migrate seasonally.  Dr Lisa Davenport has worked for many years in the tropics, especially the Peruvian Amazon.  Here she tells us about her intriguing work on a particular migrator, and its broader implications for nature conservation:

A foraging Black Skimmer

A foraging Black Skimmer

An unknown number of tropical species, such as certain birds, bats, and moths, migrate up and down elevational gradients over the year, tracking seasonal changes in the abundance of fruits, nectar, or insect prey. 

Others, notably birds such as warblers and some raptors, undertake much longer-distance migrations, wintering in the tropics while breeding in far-away temperate regions.

Manu National Park in Peru, where I have long worked, also has its share of migrators, along with being one of the most biologically stunning places on Earth.  Certain fish, birds, and mammals at Manu appear to move large distances during the course of the year. 

But as we begin to learn more about these migratory species, we increasingly suspect they could be vulnerable to escalating human pressures in this region.

Growing pressures

For instance, just downstream of Manu, on the Madre de Dios River, huge areas of river and riparian forest are being devastated by illegal gold mining.  Among these impacts is contamination of the rivers by toxic mercury, which is used by miners to separate gold from river sediments.

An illegal gold miner scours the forest soil  (photo by William Laurance)

An illegal gold miner scours the forest soil (photo by William Laurance)

Since 2010, biologists at Cocha Cashu Biological Station at Manu have used cutting-edge satellite telemetry to track some of the park’s rare and endangered birds -- many of which are very poorly known.  One key reason to do this is to learn where these species go when they move outside the park, where they may be highly vulnerable.

In a new study, I and my colleagues report our research on Black Skimmers (Rynchops niger), an elegant bird that skims over water surfaces while flying, in order to catch unwary fish.  To do this it uses its uniquely elongated lower beak, which it drags through the water and which instantly snaps shut when it contacts a fish. 

We found that Skimmers tagged in Manu move extremely long distances both during and outside their breeding season. 

A Black Skimmer feeds its chick

A Black Skimmer feeds its chick

'Albatrosses of the Amazon'

I would liken our Black Skimmers to “Albatrosses of the Amazon" -- they fly surprisingly long distances, even in the breeding season, and seem to soar effortlessly. 

We found that some Black Skimmers move not only to other watersheds in Peru but even to other nations, including Brazil and Bolivia, during their breeding season.  Unfortunately, some of these areas are being severely degraded by illegal gold mining. 

Remarkably, some of the birds tagged inside Manu even crossed the Peruvian Andes -- flying above 5,000 meters in altitude to cross the towering Andes mountains -- in order to spend their non-breeding season along the Pacific coasts of Peru and Chile. 

But the Skimmers face hazards on the Pacific coast as well.  Many of the natural wetlands they need for feeding are being severely depleted by the extraction of freshwater for agriculture

Some Skimmers may go even farther afield.  One bird radio-tagged in Manu moved not to the Pacific but southeast to Bolivia and then even further to Paraguay.  Its transmitter stopped at that point but it may have been heading to Argentina’s Atlantic coast, where large numbers of Skimmers are known to summer.

New threats on the horizon

With rising development pressures, threats to large-distance migrators like Black Skimmers will only increase.  Both Peru and Brazil plan to dramatically increasing the damming of wild rivers in the Amazon and Andean headwaters.   Agriculture and mining activities are also expanding apace.

Scores of new dams are being planned (yellow) in the Amazon-Andes region (blue symbols indicate existing dams).

Scores of new dams are being planned (yellow) in the Amazon-Andes region (blue symbols indicate existing dams).

Species that need freshwater for survival and migration, and the ecological processes that sustain such species, will be intensely vulnerable

The recent collapse of a poorly constructed mining dam on the Doce River in Brazil devastated aquatic wildlife across a vast area that stretched for more than 500 kilometers to the sea. 

The lax environmental standards that allowed this catastrophe to occur should give us all pause, as we consider the avalanche of new development projects slated for the greater Amazon region.

Especially alarming is how little we know about the ecology of the Amazon and its many natural denizens -- some of which evidently traverse and require vast areas of habitat for survival.

 

Wildife struggle in an increasingly noisy world

We live on an ever more-populous planet, pulsating with human-generated noises of every description.  As the din of humanity grows ever louder, what will this mean for wildlife?

White-crowned sparrow: stressed-out by noise

White-crowned sparrow: stressed-out by noise

It's an important question.  Across the U.S.A., for example, nearly nine-tenths of the population experiences artificially elevated sound levels.  In the world's oceans, noises from commercial shipping alone have risen an estimated 16-fold in recent decades.

The most ubiquitous noise-making structures humans create are traffic-laden roads, which already crisscross the Earth and are projected to increase in length by some 25 million kilometers by mid-century—enough to encircle the planet more than 600 times.

A recent study by Heidi Ware and colleagues used an innovative ‘phantom road’ to assess how road noise affects migrating bird species.

Working in Idaho, USA, the authors laid out an array of loudspeakers to mimic road sounds, which they turned on and off periodically to judge the birds' responses.  They also captured birds using mist-nets to assess their overall body condition.

The authors found that bird abundance declined by about a third near the phantom road, with some some noise-sensitive species avoiding the area.

In addition, even birds that remained near the phantom road often fared poorly, having lower body weight and worse overall condition than birds captured elsewhere. 

The authors attributed this to the fact that the birds were often startled by sudden road noises -- and so spent more time looking around for predators and less time feeding. 

A graph (sonogram) of road noises, above a logging truck.

A graph (sonogram) of road noises, above a logging truck.

This is particularly bad news for migratory birds, which are already stressed out by the huge exertions of migrating vast distances.  More noise disturbance could mean that more birds will starve to death while trying to migrate.

In an independent perspective piece on this article, ALERT director Bill Laurance emphasizes that the rapidly expanding footprint of roads and other infrastructure across the planet is invisibly degrading habitat quality for noise-sensitive species.

Laurance suggests that many kinds of species could be affected by human-generated noises. 

For instance, might sensitive marine species, such as echolocating whales or migratory fish, avoid noisy regions such as high-volume shipping lanes or areas where naval vessels regularly pierce the oceans with high-intensity sonar?

Could echolocating bats be distressed by roaring airplanes or even by the steady whine of wind farms or other infrastructure? 

For that matter, might even hiking trails frequented by ecotourists or researchers reduce local wildlife activity, as has been observed in protected areas in California and Indonesia?

The oceans are getting noisier too.

The oceans are getting noisier too.

The findings of Ware et al. suggest that human-generated noises can be serious stressors for some wildlife.  This is an alarming prospect in a world ever more beset by human-induced noises.

For instance, nowhere in Costa Rica’s iconic La Selva Biological Reserve can one avoid hearing the incessant thrum of a nearby highway.  Many other nature reserves are suffering a similar fate, underscoring the urgency of limiting new roads in protected areas and devising strategies to limit noise disturbances where roads already exist.

For wildlife and for humans too, quiet places on the Earth are becoming increasingly rare and precious.

The global collapse of the great animal migrations

In our modern world we are accustomed to seeing large-bodied species in decline.  Elephants, rhinos, tigers, whales, sharks, big trees -- the list goes on and on.

But there's another large biological phenomenon that is at least as vulnerable -- the great animal migrations.

Move or die: Cape Buffalo in Africa

Move or die: Cape Buffalo in Africa

Seasonal movements are crucial to the survival of most migratory animals.  And nearly everywhere one looks, migrations are collapsing.

In the plains of the American Midwest, the once-thunderous migrations of Bison and other large wildlife have virtually disappeared.

In northern Cambodia, the great migration of Asian Elephants, Gaur, and other large mammals -- known as the "Serengeti of Indochina" -- have vanished.

On the island of Borneo, large-scale movements of Bearded Pigs and Sun Bears -- in response to pulses of fruit availability -- are collapsing and causing massive animal die-offs, as poignantly illustrated by this video of a starving Sun Bear.

In the western Pacific, stunning annual migrations of shorebirds -- with some species traversing from Alaska to Australia and back each year -- are being rapidly eroded by runaway development of coastal shorebird-foraging sites, most dramatically in China and the Koreas.

Critical feeding ground for stressed-out migrants

Critical feeding ground for stressed-out migrants

In the Mojave Desert, a proposed solar-energy project would imperil the seasonal migration of Bighorn Sheep -- as highlighted recently by ALERT member Thomas Lovejoy and Harvard biologist Edward Wilson.

And in the iconic Serergeti Plain of Africa, a proposed highway would slice directly across the route of migrating wildebeest and scores of other wildlife species, potentially imperiling the greatest surviving migration on Earth.

David Wilcove at Princeton University has long studied animal migrations and their demise.  He makes a key observation: nobody has ever set out to destroy a great migration. 

Instead, migrating animals are being forced to endure an ever-growing array of human pressures -- new roads, dams, farms, cities, overhunting, persecution, and myriad other threats. 

And then, one day -- seemingly without warning -- the migration just stops.  The salmon runs collapse.  The last surviving Passenger Pigeon disappears.

As humans gobble up ever more of the planet, saving the Earth's last great migrations is going to be one of the greatest of all challenges facing conservationists. 

That it is an enormous challenge makes it not one bit less important. 

Heated debate over boreal forests

ALERT is achieving a new milestone today by hosting its first scientific debate.  This focuses on the fate and condition of the world's vast boreal forests.

Clearcut logging in a Canadian boreal forest

Clearcut logging in a Canadian boreal forest

The debate arose over a recent paper led by Nick Haddad and colleagues (of which ALERT members Tom Lovejoy and Bill Laurance were coauthors).  Haddad and colleagues asserted in their paper -- and also conspicuously in their various press coverage -- that the only two remaining areas of large, intact forest on Earth were the Amazon and Congo Basin.

Boreal forest researcher Jeff Wells takes serious issue with this contention.  Below is Wells' complaint, followed by a response from Nick Haddad and another of his coauthors, Joe Sexton, who actually conducted the analyses at the heart of this scientific tussle.

All this is then followed by a synopsis of the debate by boreal forest expert Corey Bradshaw, an ALERT member and professor and senior researcher from the University of Adelaide in Australia.  Bradshaw was not involved in either study. 

Read away!

THE COMPLAINT BY JEFF WELLS

The paper “Habitat fragmentation and its lasting impact on Earth’s ecosystems” by Nick Haddad and 23 co-authors published in the 20 March, 2015 issue of Science Advances provided an incredibly important documentation of the many and varied negative impacts to biodiversity that result from human-caused large-scale fragmentation of intact forest habitats.  Although there are regional differences in the ways in which fragmentation impacts various biodiversity features, the effects are largely generalizable across the world’s forests.

There are a few regions of the globe where there remains large tracts of forest that are not fragmented by human activities—so-called primary forests.  These areas have been mapped in a number of ways over recent decades and all show five large areas of remaining primary forest.

The largest are the North American Boreal Forest, the Siberian Boreal Forest, the Amazon Forest followed by the Congo Basin Forest and the forests of New Guinea and other parts of Indonesia. In fact, some analyses indicate that the world’s largest single intact blocks of forest habitat are now found in the Amazon and in Canada’s Boreal Forest.

Given these facts it was astonishing and disappointing to see in the paper, a map purporting to show forested areas of the globe that are most impacted by fragmentation (defined in the paper as “the division of habitat into smaller and more isolated fragments separated by a matrix of human-transformed land cover”) that portrayed the North American boreal forest as heavily fragmented rather than intact as it truly is.  In the paper the authors write that they are presenting “a global analysis of the fragmentation of forest ecosystems, quantifying for the first time the global hotspots of intensive historical fragmentation.”

They go on to say that their analysis showed that “nearly 20% of the world’s remaining forest is within 100 m of an edge — in close proximity to agriculture, urban, or other modified environments…”

Clearly the implication in this statements and others in the paper is that the mapping analyses presented in the paper intends to portray the world’s forest ecosystems that are most impacted by anthropogenic fragmentation.  In fact, the map in the paper shockingly indicates that the most northern portions of the Boreal Forest region of North America are among the most fragmented in the world.

Anyone with knowledge of northern and Arctic regions would likely be rather astonished by this portrayal given the incredible lack of human industrial fragmentation in this remote and generally inaccessible part of the world. The inaccurate and misleading map and analysis is the result of a mischaracterized data set that labels natural fires, intact peatland and tundra (far from any human industrial footprint) as the same as clearcuts, areas cleared for agriculture or mines, roads, powerlines and other human caused fragmentation.

While as a scientific issue this mischaracterization is serious enough, more troubling is the fact that media stories about the paper included quotes attributed to the first author like this one in a story in The New Yorker:

“There are really only two big patches of intact forest left on Earth — the Amazon and the Congo — and they shine out like eyes from the center of the map.”

Or this statement in Climate Progress:

“Haddad was surprised by the degree that Boreal forest in Canada and Siberia has already been sliced up.”

These statements are fundamentally incorrect and are a serious blow to conservation initiatives in the massively large, truly intact Boreal Forest region of North America where incredible efforts are underway that are succeeding in achieving some of the world’s largest forest conservation gains.

Canada’s Boreal Forest region (an area of approximately 5.6 million square kilometers) is estimated to contain 25% of the world’s remaining primary forest within its Boreal Forest region, storing a minimum of 208 billion tonnes of carbon, supporting some of the world’s largest populations of northern large mammals including some that undertake the world’s last large-scale annual migrations and hosting 1-3 three billion nesting birds, most of which migrate south to populate temperate and tropical forests.

This vast intact forest region continues to be inhabited by to hundreds of indigenous communities that maintain their cultural traditions including harvesting native fish and wildlife for subsistence.

Over 870,000 square kilometers of new protected areas have been established across Canada’s Boreal Forest region in the last 15 years and the governments of Ontario and Quebec are pursuing conservation visions that together would strictly protect (IUCN categories I-IV) an additional 858,000 square kilometers of intact, primary forest. 

In the Northwest Territories, over 425,000 square kilometers of new protected areas and interim protected areas are the result of leadership of indigenous governments that have developed sophisticated land-use plans combining traditional knowledge and Western science approaches.

What is particularly tragic is the portrayal of North America's Boreal Forest as one of the parts of the world that is most highly fragmented by human industrial activities.  Scientists and conservationists working in the world's last wildernesses should become more familiar with the threats across ecosystems and regions, in order to accurately portray reality on the ground.  This will allow us to protect these ecosystems while there is still time to do so.

A boreal forest in flames

A boreal forest in flames

THE RESPONSE BY NICK HADDAD AND JOE SEXTON

Dr. Wells’ comments regarding the ecological importance of boreal forests are valuable.  The boreal forest houses enormous stocks of carbon; is the origin of many major rivers transporting nutrients to and from the Arctic Ocean; and its trophic system provides essential ecosystem services to human communities.  Dr. Wells confirms what is shown in our Figure 1 when pointing out that the boreal forest is one of the greatest remaining expanses of forest on Earth.

We agree with Dr. Wells’ assertion of the conservation value of boreal forest, and our global forest analysis in no way contradicts it.  Compared to temperate and tropical forests, the boreal forest is much less impacted by human land-use change. 

Whereas the forests of temperate and tropical biomes (except the interior forests of the Amazon and Congo Basins) are heavily fragmented by human land use, edges of the boreal forest are primarily natural.  Boreal-forest edges arise predominantly from climatological and edaphic features (i.e., the taiga-tundra ecotone), from hydrological features (the prevalence of rivers and small water bodies), and from acute disturbances such as fires and insect outbreaks (see a recent comparison of natural and human created edge effects in boreal forest).

Whereas logging impacts some regions — including much of British Columbia and Scandinavi— these areas are a comparatively small portion of the total area.  Yet even this distinction is increasingly eroded by human impacts, as recent fires in the Siberian boreal forest have been found to be largely human in origin.

It is currently impossible to discriminate natural from human-induced edges, and so our global analysis did not attempt to do so. This contrasts with our experimental analyses which comprise the bulk of our paper, and which are focused on effects of human-caused fragmentation.

In retrospect, we should have emphasized this distinction; we regret the confusion it created.  Our Figure 1 does not “portray the world’s forest ecosystems that are most impacted by anthropogenic fragmentation,” (Wells’ assertion) but instead simply maps globally the distance of each forest pixel to the forest’s edge.  Regardless, Wells’ assertion that the boreal forest is not fragmented raises an important distinction between natural and human-created edges.

Many of the effects of natural and anthropogenic fragmentation are identical — sunlight and wind penetrate a forest edge regardless of its origin. However, many edge effects — including species invasions, especially by species associated with humans — are not.

As is often the case with the conveyance of scientific findings to the public, the popular media focuses on one or two key points and disregards complexities.  The primary objective of our paper was to synthesize long-term experiments documenting the effects of habitat fragmentation. The spatial analysis of forests was included to alert our audience to its global footprint, whether natural or anthropogenic. 

Given one figure and two short paragraphs, we could only portray this complexity from one aspect — namely habitat edges.  The popular media focused on the Amazon and the Congo forests, the two areas with the least areas of edge, but did not cover the distinction between natural and anthropogenic disturbance.

We share Dr. Wells’ eagerness to overcome the current technical inability to discriminate natural from human-induced vegetation change in the satellite record.  We and a large community of researchers are working on precisely this problem.  We look forward to specifying the agency of habitat fragmentation in the years to come.

To reiterate, we agree with Dr. Wells about the great need to conserve boreal forest.  We are at the same time pleased that Dr. Wells recognizes our study’s central finding: that human-induced habitat fragmentation threatens forests across the globe, leading to long-term decline in the diversity and function of ecosystems.

Long-term experiments and global analysis of the extent, pattern, and dynamics of forest change will continue to advance understanding of the impact of and conservation prospects for landscapes fragmented by people.

Massive stockpile of boreal timber

Massive stockpile of boreal timber

A PERSPECTIVE FROM AN INDEPENDENT EXPERT, COREY BRADSHAW

Missing the forest despite its trees

Despite its immense size, there is little doubt that the ugly second cousin of forest conservation is the boreal region covering much of Alaska, Canada, Fennoscandia, and Russia.  Indeed, extending some 1.4 billion hectares, of which well over 60% is found in Russia alone, the entirety of the boreal forest is more than double the area of the Amazon forest.

Yet despite this massive expanse, the impressive biota it shelters, and its important contribution to the global carbon, nitrogen and oxygen cycles, the boreal is an oft-overlooked region in terms of global conservation priorities and possibilities.

The exchange between Haddad & Sexton and Wells regarding the former researchers’ recent paper highlights this problem, of which even many expert ecologists are often only vaguely aware.  Wells takes particular issue with Haddad and colleagues’ assertion that the boreal forest is highly fragmented, claiming to the contrary that the (North America) boreal forest is “… truly intact … ”.  While Haddad and Sexton respond that they did not differentiate between ‘natural’ and human-caused fragmentation, my view is that the exchange misses some important concerns about the state of the boreal forest.

Wells correctly points out that the boreal zone in North America is “massive”, but can his other claim -- that it is “truly intact” -- stand up to scrutiny?  Citing one of my own papers from 2009 to demonstrate (correctly) that the boreal forest of North America holds a stunning array of species, Wells neglects to highlight that in that same paper we also identified the extensive, artificial fragmentation that has occurred there and in other parts of the boreal zone over the last few decades.

For example, we showed clearly that only 44% of the entire biome is considered to be ‘intact’, defining the term precisely as “areas over 500 square kilometers, internally undivided by infrastructure (e.g., roads) and with linear dimensions greater than 10 kilometers”. 

Satellite imagery has also confirmed that between 2000 and 2005, the boreal biome experienced the largest area of gross forest cover loss compared to any other.  Despite recent evidence that so-called edge effects (characteristics of a disturbed matrix that penetrate some distance into habitat fragments) are probably of a smaller spatial magnitude in boreal compared to other biomes, it is disingenuous to claim that North America’s boreal forests are “truly intact”.

Wells' perspective also ignores the intense historical and current fragmentation to the largest boreal forest region in Russia.  Between 1988 and 1993, Russia lost an average of 1.1 million hectares of forest per year due principally to logging.  An increase in fire and insect outbreaks due to direct (fire) and indirect (climate-driven insect outbreaks) human pressures has eroded the area even further.

Add these observations to mounting evidence that the boreal forest has already or is about to become a net carbon source due to direct (logging, fire) and indirect (climate change, insect outbreaks) human influences, and it is counter-productive in any conservation sense to purport that the boreal zone is anything but a highly modified and increasingly disturbed biome.

I can understand that anyone used to the images of forest devastation from South East Asia, the Amazon, or many parts of Central Africa might be convinced that the boreal forest is comparatively intact -- for it is indeed relatively more contiguous.  However, the extent of the boreal fracturing can be easily missed if not observed from broader spatial scales.

From my own personal experience in northern Alberta over 20 years ago, the sight of a vast expanses of boreal forest criss-crossed with seismic exploration lines and clearcuts from logging testify viscerally to our capacity to modify even the seemingly infinite spans of remote boreal wilderness.  While the boreal forest might not have the same human population densities or experience the same degree of legal and illegal forest conversion as the tropics, it is nonetheless a highly and increasingly stressed ecosystem.

Fortunately, we still do have the opportunity to limit the worst ravages that deforestation, climate change and fire could wreak there, but we have to get a lot more serious about measuring, recognizing, and limiting the damage that we as a society seem so desperate to render.