Bird Flew

Snow geese4When the red ants discovered that a new variety of canned goods had arrived, they mounted guard around the cassoulet. It wouldn’t have been advisable to leave a freshly opened can standing; they’d have summoned the whole nation of red ants to the shack. There are no bigger communists anywhere. And they’d have eaten up the Spaniard too. –Louis-Ferdinand Céline (1934)

Conservation biology explores how best to protect and restore biodiversity. The applied science aims at maintaining diversity at a variety of levels of biological organization, including genes, subspecies, species, ecosystems and biomes.

But conservation efforts aren’t interested in preserving things alone. Ecologies are defined by processes; competition, predation, symbioses, and higher-order nutrient cycling among them. Organisms are actualized in part by the actions they take upon, or with, each other.

In any environment we look at we’ll find a food web of some sort. In losing species, local ecologies can degrade and the ability of an ecosystem to buffer a disturbance of one sort of another can be compromised.

What is the current state of biodiversity?

Global extinction rates are clocking in roughly 100-1000 times faster than the historical or natural background. The fossil record indicates that for every thousand mammalian species, less than one on average was lost during any millennium. For birds, mammals and amphibians, the recent rate of extinction is approaching a hundred extinctions per thousand species per thousand years. Incipient losses are projected to be a thousand times the current rate.

Along with losing the natural world as we know it, biodiversity losses, disconnecting ecological relationships, will harm people, and indeed already have. We’ll forever lose sources of food, medicines, industrial products, and, to use a reductionist term, ecosystem services such as water purification, and erosion, pest and climate control.

We are losing cryptic diversity as well. Subspecies, genetically distinct populations of a species, are going bye-bye. The Greater Prairie Chicken, a subspecies of grouse Tympanuchus cupid, lives in the prairies of the Midwest. Its East Coast cousin, The Heath Hen, much smaller and inhabiting coastal heath land, went extinct in 1932. Many other populations across even ‘healthy’ species have declined at rates at which they are in danger of extirpation.

Why are species declining?

Human intervention–logging, agriculture, water diversion, pollution, and development–is destroying and degrading natural habitat.

Much of the habitat that remains is fragmented in such a way that continuous populations are subdivided into smaller populations, placing them in greater danger of winking out if by chance alone. Those which survive, including those of the panda, isolated by China’s new network of roads and rail, are in danger of inbreeding, losing the very genetic diversity needed for the kinds of evolutionary response such changes demand.

Introduced species can destroy native species and ecosystems. Feral cats, accidentally introduced, endanger native birds of Macquarie Island, as is, ironically under the resulting ecological regime, the cats’ removal. On several Caribbean islands the mongoose drove many reptiles and birds to extinction.

Overharvesting can destroy populations. Hunting, fishing or collecting so many young or reproducing individuals can reduce a population’s capacity to replace itself. Overharvesting led to the extinction of the Passenger Pigeon in North America, the Great Auk throughout the North Atlantic, the Tasmanian wolf in Australasia, the Moa in New Zealand, the Dodo of the Indian Ocean island of Mauritius, and increasingly many of our common fish stocks.

The effects are axiomatic, indeed fateful. As Bill Maher recently put it, in what our Soylent Green descendents may consider less pottymouth rant than inspired prophecy,

It’s been big news the last couple weeks that the food supply is not what it appears to be. I hate to break it to you haute cuisiners. But did you know your Chilean sea bass is neither Chilean, nor bass, nor from the sea? It’s koi from the pond out front that the valet guys piss in. And your mahi-mahi is really made of mercury-drenched bottom feeders like tilefish that squirm along the ocean floor, eat feces, and occasionally provide legal representation for Donald Trump…

Y’know one reason why there’s so much fish mislabeling now? It’s because they don’t have the heart to tell you that the fish you like are gone. Eighty-five percent of the world’s fisheries are either fully exploited, overly exploited or collapsed. Y’know where fisherman can’t find cod? Off Cape Cod…

*

Human intervention can destroy habitats in other ways. Sometimes our impact can cause a species’ population to increase to such a size as to annihilate native habitats. Extinction isn’t the only way to rewire an ecosystem.

Ecologist Robert Rockwell and his colleagues have followed the fortunes of the mid-continent population of lesser snow goose, Chen caerulescens caerulescens.

Historically, the geese wintered in a narrow strip of coastal marsh along the Texan and Louisianan Gulf Coast. In the 1940s, developers began to turn the coastal salt marsh into shopping centers and apartment buildings.

The waterfowl—as have many species of bats similarly impacted—wouldn’t just die off nicely, thank you. The geese began to winter elsewhere, specifically in agricultural fields, eating the best rice, corn and wheat the United States can produce as far north as Minnesota. The geese now sup on high-quality food, pudging up to their reproductive weights in a shorter time than it once took on salt marsh grub.

As a result, the snow goose population exploded, growing from 1.5 million in 1970 to more than 12 million today. La Pérouse Bay, only one of many goose summer breeding grounds along and north of Hudson Bay, supported 2500 pairs of geese when Rockwell first started his studies. There are now more than 60,000 pairs.

Canada and the US meanwhile established wildlife refuges for birds during their spring and fall migrations. Snow geese took full advantage. Now with federally protected sanctuaries and an abundance of newly exploited winter grain, lesser snow goose numbers began growing at about 7% per year.

While the flocks thrill bird watchers, the impact of goose numbers on northern ecosystems has entered a critical stage.

During the spring, geese along the Hudson Bay coastline feed by grubbing. By their serrated beaks they pull out and eat the underground portions of the plants. A grassy patch can quickly be turned into bald dirt.

Shoot pulling occurs in more inland settings where the birds grasp the stems of water sedge near their base and pull them from the soil. The nutritious base is consumed leaving the dead leaves of the previous year to accumulate in the fresh water marsh.

With the surface vegetation removed, soil moisture is lost and salinity increases to as high as three times that of sea water. Salicornia (a non-nutritious salt-tolerant plant) replaces the lost grasses and sedges. The salinity also kills willows that typically provide shelter and food to passerine birds and ptarmigan.

Grubbing helps form and enlarge hyper-saline “goose ponds” in the once continuous coastal meadows. Few if any aquatic invertebrates, a key source of nutrition, survive these ponds, reducing the food web’s diversity.

Goose grubbing also destabilizes the soil, leading to still greater erosion during the spring melt and run-off.

*

The goose’s destructive foraging and the attendant erosion can be seen in stunning ‘before’ and ‘after’ shots taken thirteen years apart at one of the primary feeding flats at La Pérouse Bay. A lush landscape circa 1984 turned into a dried-out wasteland by 1997.

Is the salt marsh degradation really the goose’s fault? Rockwell’s team set up exclosures that kept the geese out. The resulting blossoms pinned blame on the birds.

The geese have eaten so much of their own habitat out from underneath themselves that they’ve begun to migrate to finer pastures (which they promptly destroy). South of La Pérouse Bay, goose degradation has extended all the way to the boreal forest where black spruce and tamarack are killed by way of the soil’s hyper-salinization. The forest was once home to many song birds and grouse.

Panning back, remote sensing shows changes in available plant biomass. The migration patterns and attendant habitat loss are, yes, obvious from space. Upon an area’s ruin, the geese move on. The map’s green ‘unchanged’ region, however, gives a false impression of the extent of the remaining ecosystem. In actuality, much of the vegetation there is unusable to the geese (and many other species).

As LPB degrades, the snow geese have swiftly expanded into Wapusk National Park, Akimiski Island, and Cape Henrietta Maria. A combination of factors led to a major influx of snow geese at Thompson Point, for instance, starting 2001.

The snow periodically melts before the geese migrate back from down south. In those years, the Hudson Bay flocks tend to congregate in the Thompson Point region, where drainage is better and the forage more accessible.

Spring 2001 produced a particularly drier Point and over 250,000 snow geese chose to forage and nest there, from the immediate shoreline to five kilometers inland, where the intensity of grubbing and shoot pulling was severe.

To quantify the damage, Rockwell’s team sampled across multiple transects north and south of the Point itself. Over 60% of the landscape north and south was either rendered barren or sustained heavy damage.

How to reverse the damage? Snow fences can keep snow cover over the landscape for a longer time, protecting it from geese grubbing. Hunting and collecting eggs–depending on where such interventions are pursued–are means by which to more directly control the size of the population.

It seems, then, to our surprise given overharvesting, that the stereotypical conflict between hunters and ecologists can be set aside here. Hunting can also play an important role in protecting the integrity of local ecosystems.

*

Ecological impacts clearly can be felt across large geographic extents, including areas which at first glance appear functionally unrelated.

Development along the Gulf of Mexico coastline led to a cascade of effects, including behavioral and geographic shifts in a migratory waterfowl. Wintering lesser snow geese switched to foraging on the great expanse of Midwest agriculture. The resulting population explosion devastated breeding grounds thousands of miles north of the Gulf.

Big Food’s collateral damage meanwhile extends out from beyond diabetic kids in Harlem and South Side. The human impacts driving biome change in the Arctic—deforestation, monocropping, carbon saturation—are being felt through pathways other than just the atmospheric.

There appear disease costs as well. In the course of colonizing our planet’s natural habitats—some 40% of the world’s usable land now supports agriculture—we may have also unintentionally expanded the interface between migratory birds switching ecological regimes and domestic poultry, with fundamental implications for epizooses, including for our poster bug, bird flu.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: