GAUGING MANKIND’S ECOLOGICAL FOOTPRINT

In the wake of the World Summit on Sustainable Development in Johannesburg, South Africa, there’s been a lot of talk about how to balance human needs with the health of the planet. Ecologists have been trying to measure the impact of humans on the environment for a number of years, with some sobering results. The Great Lakes Radio Consortium’s Daniel Grossman went to the New York Botanical Garden recently to gauge mankind’s ecological footprint:

Transcript

In the wake of the World Summit on Sustainable Development in Johannesburg, South
Africa, there’s been a lot of talk about how to balance human needs with the health of the
planet. Ecologists have been trying to measure the impact of humans on the environment
for a number of years, with some sobering results. The Great Lake Radio Consortium’s Daniel Grossman went to the New
York Botanical Garden recently to gauge mankind’s ecological footprint.


[Rain forest sounds, misters, tinkling of water, rain falling on leaves]


To get a good sense of the impact humans are having on earth, you could travel for weeks
on intercontinental plane flights, river boats and desert jeeps. Or, as Columbia University
biologist, Stuart Pimm suggested, visit a botanical garden. There, under the glass and
ironwork of a conservatory, Pimm says you can see a resource that humans are
over-using – Earth’s most important resource, its plant-life.


“We’re sitting in the rain forest here at the New York Botanical Society. And it’s a riot of
green.”


Professor Pimm says here beneath the misters in the Tropical Rain Forest Gallery is a
good place to start a whirlwind tour of Earth’s greenery. The air is heavy with moisture
and sweet-smelling.


“Rain forests are some of the most productive parts of the planet. They grow extremely
quickly and they are therefore generating a lot of biological production.”


What Pimm calls biological production most of us know as plant growth. Biologists say
all this green growth in tropical forests and elsewhere on Earth is the foundation upon
which all life rests.


“Everything in our lives is dependent upon biological productivity – everything that we
eat, everything that our domestic animals eat.”


And everything that every other animal eats as well. In a recent book, Pimm painstakingly
tallies up how much biological productivity we use. He starts with the rain forest. In the
last 50 years, loggers and settlers have cut down 3 million square miles of lush tropical
forests. Much was cut down for subsistence agriculture, a purpose Pimm says it serves
poorly.


“Although the tropical forest looks rich and productive, it is a very special place. And
when you chop that forest down the areas that replace it often become very, very much
less productive.”


[Sound of walking around conservatory]


Pimm speaks of the toll on greenery of cities and roads and of land converted to farming
in temperate regions such as the U.S. Midwest. Then, trekking along the botanical
garden’s gravel paths, he leaves behind the tropical mists and steps into the dry heat of a
Southwestern desert. Deserts and other dry lands are not very productive, but they
account for a substantial fraction of Earth’s land surface. Most of it is grazed by flocks of
sheep, goats, camels and cattle, often causing severe damage to vegetation. When these
uses are added to the other impacts of humanity on earth’s bounty, the results are
surprisingly large.


“What silence has shown is that we are taking 2/5ths of the biological production on land,
a third from the oceans. And that of the world’s fresh water supply, we’re taking half.”


[Fade out sound of conservatory. Fade up sound of Texas frogs.]


[Sound of plane engines]


Frogs and toads croak out a spring mating ritual in a concrete drainage ditch. Nearby, a
pilot practices maneuvers in a small plane occasionally drowning out the amphibian
serenade. Living in culverts, sharing the night with droning engines, these wild animals
are never completely free of human influences. From his Stanford University office,
Professor Peter Vitousek says wherever you look, the din of human activities is
interrupting and crowding out other species. Vitousek made one of the first attempts to
tally the impact of people on plant productivity in 1985.


[Frogs fade out in time for Vitousek’s act]


“The message to me was that we are already having a huge impact on all the other species
because of our use of the production of Earth and the land surface of Earth. That’s not
something that our models predict for some time in the future or something that we’re
guessing at on the basis of fairly weak information. It’s something that we’re clearly
doing now. That’s already happening.”


Many ecologists say this conclusion is beyond doubt. What they can’t say is whether
human domination of so much of nature’s output is good or bad. University of Minnesota
Professor David Tilman says as a member of the human race himself, he appreciates the
comforts in clothing, shelter and food our lifestyles buy us. And he acknowledges that the
survival of our own species is probably not imperiled – at least for the moment – by the
destruction of others. Still, he wonders if someday we’ll regret today’s resource intensive
practices.


“I think the more relevant question to me is, ‘Are we doing this wisely?’ ‘Are we wisely
appropriating the resources of the world?’ So, my concern is that we live in a balanced
way – a way that is sustainable through generations – that we leave our children and
grandchildren the same kind of world that we have.”


An expert on the impacts of agriculture, Tilman says we’re using up more resources than
can be replaced. He says if we don’t grapple with these important issues now, by the time
the human population reaches eight to ten billion or so people later this century, it might
be too difficult for us to do enough to save the planet’s life as we know it today.


For the Great Lakes Radio Consortium, I’m Daniel Grossman.

Curbing Nitrogen Pollution

Across the country, forests, streams and coastlines are getting extra doses of nutrients containing the element nitrogen. Researchers say the long-term impact of these unwanted compounds on the environment could be serious. The Great Lakes Radio Consortium’s Daniel Grossman reports on some efforts to reduce nitrogen pollution:

Transcript

Across the country, forests, streams and coastlines are getting extra doses of nutrients
containing the element nitrogen. Researchers say the long-term impact of these unwanted compounds on the environment could be serious. The Great Lakes Radio Consortium’s Daniel Grossman reports on some efforts to reduce nitrogen pollution:


A thunderstorm soaks the land and lights the sky. The electric jolts of the lightning change nitrogen in the air into compounds needed for plants to grow. Lightning, as well as microbes in the soil, converts annually nearly 100 million tons of atmospheric nitrogen into plant nutrients. Humans make the same compounds in factories and call them fertilizer, a mainstay of agriculture. Between these synthetic chemicals and a smaller quantity of related compounds produced when fossil fuels are burned, humans produce more nitrogen-rich nutrients than nature makes on the seven continents. University of Minnesota ecologist David Tilman says such extra nutrients are a concern.


“Right now half or more of the nitrogen we put on a farm field just washes through the soil and down into the groundwater into lakes, rivers, streams and into the ocean.”


This wasted nitrogen often travels great distances causing widespread damage. Tilman says on land, the nutrients cause exotic weeds to outgrow native plants. In the ocean, the nutrients cripple critical habitats. The ecologist says nitrogen pollution must be cut. One place to start is on the farm.


“We have to find some way to grow crops where the crops take up much more of the nutrients that we apply.”


(Sound of walking through grass. Quiet bird calls in background.)


Near Chesapeake Bay, farmer and agricultural scientist Russ Brinsfield walks across a patch of tall dry grass.


We’re on the edge of a field, about a sixty-acre field of corn, on the beautiful Eastern Shore of Maryland.


This field is a research plot at the Maryland Center for Agro-Ecology. Here Brinsfield is studying agriculture’s environmental impact. Chesapeake Bay’s waters have high concentrations of farmer’s nutrients, causing blooms of the toxic algae Pfiesteria. The pollution has also caused declines in sea grass beds. Brinsfield says solutions to the problem fall into two categories.


“The first series of practices are those practices that we’ve been able to demonstrate that by a farmer implementing them he can reduce his inputs without affecting his outputs… that at the end of the year have added profit to his bottom line.”


For instance, testing the soil’s nitrogen level before fertilizing. And splitting fertilizer applications into two doses rather than one so that nutrients are added only when plants need them. Such simple measures are good for environment and the bottom line. Brinsfield says in the last 10 years most farmers on the Eastern Shore of Maryland have cut fertilizer use this way. Then there’s the other category of improvements.


“We’re going to have to do some things-ask some farmers to do some things-that may cost them more to do than what they are going to get in return from that investment.”


For example, in the winter, many fields here are fallow and bare. That means top soil erodes when it rains, taking with it residual fertilizer. It wasn’t always this way.


“I can remember my dad saying to me, ‘every field has to be green going into the winter, Son.’ So all of our fields were planted with rye or wheat or barley. It served two purposes. First, the animals grazed it. And second, it held the soil intact.”


And intact soil retains its fertilizer. Such winter cover crops also prevent fertilizer loss by storing nutrients in plant leaves and stalks. This used to be dairy country and cover crops grazed by cows made economic sense. Now farmers mostly grow grains. Planting a cover crop could cut nitrogen flow from farms by 40 percent but it costs farmers about $20/acre and provides no economic benefit to them. Brinsfield says farmers need an incentive.


“For the most part, farmers are willing to participate and to do those things that need to be done, as long as they can still squeak out a living.”


To help them squeak out a living, the state pays some farmers to sow cover crops. The state also pays them to plant buffers of grass and trees that suck up nutrients before they leave the farm. Today farms in six states that are part of the Chesapeake’s huge watershed contribute about 54 million pounds of nitrogen to the bay. The goal is to cut this figure approximately in half by two thousand and ten. Robert Howarth, a marine biologist and expert on nitrogen pollution at Cornell University, says though ambitious, this target can be achieved.


“I think most of the problems from nitrogen pollution have relatively straightforward technical fixes. So the real trick is to get the political will to institute these.”


Howarth says much of the nitrogen problem could be eliminated with a blend of government subsidies and regulations. But more will be needed as well… solutions of a more personal nature.


(sound of Redbones Barbeque)


There’s a pungent, smoky aroma in the air at Redbones Barbeque in Somerville, Massachusetts. The crowded bistro serves up a variety of ribs, chicken, sausage and other meats, dripping with savory sauces. University of Minnesota ecologist David Tilman says when someone eats a meal they are responsible for the little share of fertilizer a farmer somewhere had to apply to grow a crop. If the meal is from farm-raised animals, like the heaping plates of meat served here, the amount of fertilizer is much greater than if it’s from plants.


“It takes from three to ten kilograms of grain to produce a single kilogram of meat.”


Tilman says if Americans ate less meat, they could dramatically reduce fertilizer usage. However, per capita consumption is rising. Meat consumption is on the rise globally as well. David Tilman would like that to change. He says if current trends continue, human production of nitrogen nutrients will grow to triple or quadruple what nature makes on all Earth’s lands. Professor Tilman says that in many places the impact on the environment would be catastrophic.


For the Great Lakes Radio Consortium, this is Daniel Grossman.

The Threats of Nitrogen Pollution

  • A researcher in Rhode Island collects a sample from an algae bloom. Increased levels of nutrients, such as nitrogen, often lead to these blooms. Photo courtesy of URI Sea Grant.

From mountain summits to ocean shores, plants and animals are suffering from exposure to the chemical nitrogen. Though this element is a key building block of life, it can also be a pollutant so serious that some biologists rank its effects on par with global warming. The Great Lakes Radio Consortium’s Daniel Grossman reports:

Transcript

From mountain summits to ocean
shores, plants and animals are suffering from exposure to the chemical nitrogen. Though this element is a key building block of life, it can also be a pollutant so serious that some biologists rank its effects on par with global warming. The Great Lakes Radio Consortium’s Daniel Grossman reports:


(Sound of farm; fertilizer application)


At Welsch Farms in Jersey County, Illinois, workers are preparing the soil for planting. They’re injecting into the ground anhydrous ammonia, a man-made fertilizer. This is modern agriculture, the foundation of civilization.


“When agriculture first began about 10,000 years ago there were 4 million people living on Earth. There are now 6 billion. And the only reason we can have so many people is that we have been able to perfect agriculture.”


University of Minnesota ecologist David Tilman
says a critical element to perfecting agriculture was inventing synthetic fertilizer containing the element nitrogen, like the ammonia being applied here. Plants need nitrogen to make life’s building blocks, including DNA and proteins. So billions of pounds of factory-made nutrients are applied to crops every year. Of course, nitrogen is all around us. The air we breathe is mostly nitrogen. But this gaseous form is kind of like crude oil to a car — it needs to be chemically modified — the same way oil has to be refined — to be used. The natural refineries of atmospheric nitrogen are soil microbes that convert it to a form plants can use. But today, the dominant source of this key nutrient is not microbes. It’s fertilizer factories. These, along with nitrogen compounds created when fuel in cars and power plants is burned have doubled above natural levels the production of nitrogen nutrients.


“The problem is there can be too much of a good thing.”


Gerry Melillo is a researcher at the Marine Biological Laboratory in Woods Hole, Massachusetts. He says the problem is not just how much of this nutrient is made, but where it goes.


“Once it is biologically available, it can cascade through the environment in a variety of forms, moving to places that we as humans did not intend it to move.”


More than half of the fertilizer applied by growers is never used by plants. It percolates into ground water. It evaporates into the air and flows from fields to streams and lakes. In rare instances, water supplies become so contaminated with excess nitrogen they become unfit for human use. Nitrogen compounds in such water can replace oxygen in the blood of infants, causing a life-threatening condition sometimes called “blue-baby syndrome.”


Waterways polluted with excess nitrogen flow to the ocean. There in shallow coastal waters, it spurs algae growth. When these algae die and decompose they use up oxygen, suffocating fish. Cornell biologist Robert Howarth says this is happening in spades at the mouth of the Mississippi river.


“The nitrogen pollution coming
down the Mississippi River has created an area of about 20,000 square kilometers — that’s an area bigger than the state of New Jersey — where a lot of higher forms of life have just been wiped out by this nitrogen pollution.


The degree of damage there is unique because the mighty Mississippi drains so much farmland, but Howarth says two-thirds of U.S. coastal waters suffer some nitrogen damage. Life on land is at risk as well. Liquid fertilizers evaporate from farmers’ fields. These vapors, combined with smaller amounts of nitrogen compounds from tailpipes and smokestacks drift in the wind and fall to land as acid rain and dust.


(Sound of walking in woods)


The effect of nitrogen pollution on trees is the subject of a study at the Harvard Forest outside Boston.


“As we go up the path here there’s two research plots on either side. The high nitrogen forest is over here…”


Forester John Aber walks briskly up a steep dirt track. For the last 12 years, Aber, a professor at the University of New Hampshire, has been applying fertilizer to this plantation of mature red pine. The scientist turns off the path into a stand of tall trees.


“Some of the trees appear, actually, to be dead. And the remaining trees that are alive, the crowns are very sparse. Some foliage left at the tops and and at the ends of the branches, but it’s very open.”

“Huh, this is a pretty sick-looking forest.”

(laughs) “It is indeed. It’s looking a lot worse than it did than even a year or two ago.”


John Aber say the extra nitrogen
is probably binding up soil minerals, making them inaccessible to roots. The trees in this plot are getting big doses — 20 times the amount of nitrogen falling as air pollution. But Aber has some evidence that even smaller amounts of nitrogen — comparable to that coming from acid rain and dust — could be causing subtle forest damage.


“So it’s kind of a warning that those potential responses are out there, if we didn’t take care in controlling nitrogen pollution.”


(Fade out steps)


It’s not just forests with these responses. Half a continent away, ecologist David Tilman is studying the effects of nitrogent on native grasses. He’s been surprised by his results.


“Adding a small amount of nitrogen; just the amount that falls out of the atmosphere every year in Minnesota, year after year for twenty years, has caused us to lose a little over 30 percent of the plant prairie species that occurred at our site.”


Like many plants, native grasses are adapted
to live in low-nutrient sod. They can’t take advantage of nitrogen-rich soil.
Plants that can — like the European transplant quack grass –out-grow and
replace the natives. Tillman says it’s the gradual erosion of the
diversity of plant and animal life that may be the most serious impact of
nitrogen pollution. Tillman adds U.S. farms and factories must reduce
nitrogen pollution if this country’s diversity of life is to be preserved.


This is Daniel Grossman for the Great Lakes Radio Consortium.

Unraveling Mystery of Birds’ Night Calls

  • Ornithologist Bill Evans has been tracking down avian night flight calls for 17 years.

Many North American birds are in serious decline. But scientists aren’t sure what’s wrong because birds are hard to count. The problem is partly that birds often migrate long distances between wintering sites and summer breeding grounds. Usually, they fly unobserved at night, and in many cases scientists don’t know what route they take. However, a new technique promises to solve this problem. The Great Lakes Radio Consortium’s Daniel Grossman has our story:

Transcript

Many North American birds are in serious decline. But scientists aren’t sure what’s wrong because birds are hard to count. The problem is partly that birds often migrate long distances between wintering sites and summer breeding grounds. Usually, they fly unobserved at night, and in many cases scientists don’t know what route they take. However, a new technique promises to solve this problem. The Great Lakes Radio Consortium’s Daniel Grossman has our story:

(Sound on dock, with Evan’s whispering out bird names fades up under intro.
Continues under Grossman track, then heard in clear.)

It’s a warm spring evening on the south Texas coast. Ornithologist Bill Evans sits on a dock, listening for birds.

“Grey-cheek thrush.”

Grossman: “That high one?”

“Yeah. (makes sound). Moor hen calling behind us on the ground. Oh sorry, that’s a black-necked stilt.”

Evans has been listening to and studying these night calls since he had an epiphany at a Minnesota campground in 1985. Then a recent college dropout and avid birder, Evans was adrift, unsure what to do with his life.

“I was getting back to a campsite about two in the morning and heard an incredible flight.”

Hundreds of birds were passing overhead in nocturnal migration, including what appeared to be about 100 black-billed cuckoos.

“If you go out and look for black-billed cuckoos during the day you may see two or three. And I’m thinking, ‘wow if I had a tape recorder and could somehow document this on audiotape, I might have a pretty powerful conservation document.'”

Bill Evans got a recorder and soon was making tapes of flight calls. But his recordings were of limited use because no one knew which birds made which sounds. The melodious tunes birds perform during the day are well known. But, according to Cornell Professor Charles Walcott, the calls they make during night flights are another matter.

“If you out on an evening and listen to these birds migrating overhead you’ll hear all these twitters, most of which don’t sound anything like what a normal bird sounds like at all.”

Walcott is the former director of the Cornell Ornithology Laboratory. He says night calls may help birds keep from colliding with each other. For decades, researchers hearing these calls were frustrated knowing there were birds in flight, but unable to determine which ones.

“And to be able to recognize individual species by their calls was a dream that many people have had. And Bill is the first one that’s been able to do it on any substantial scale.”

Evans spent the next 17 years prowling migration routes to match birds with their calls. Often his only chance came in the wee morning hours, when sometimes night migrants make a single night call before settling down to eat and rest. Gradually he cracked the code.

“The herons. Amazing squawks. Black-crowned-night heron is a sort of (makes sound). Green heron is a (makes sound). Barn owl. It’s a [makes sound]. Except it’s about ten times louder than that. The dickcissel is actually a sparrow and it’s got sort of a buzzy note (makes sound).

(Sound of truck door closing and truck starting up)

The small, colorful dickcissel is why Bill Evans is here, just north of Brownsville, Texas. He’s set up a network of 15 computerized monitoring stations that listen for dickcissels in flight. It’s the first large-scale effort to track birds using night calls. The network is stretched out along a line he believes these birds cross on their way between Venezuela and the U.S. plains.

Each station has a roof-mounted microphone, connected to a computer. Most of them are at high schools – their large, flat roofs and spacious grounds reduce traffic noise – and they’re generally in a science class. And while Evans does stay up late to listen for pleasure, it’s these computers that are actually doing the work. Each day he collects the past night’s results, in a marathon drive, station by station.

(Sound of high school PA System making announcement cross fades with truck under previous track. Also mixed in sound of crowded high school corridor with students changing classes. Cross-fades with sound of classroom.)

Evans: “Come on over guys. My name is Bill, this is Dan.”

Peter: “Bill and Dan?”

Evans: “What’s your name?”

Tate: “Tate.”

Peter: “Peter.”

Bill: “Nice to meet you guys.”

Some curious students pay Evans a visit at La Ferria High School.

(Evans fades up underneath Grossman. Then heard in clear.)

Evans (to students): “…So anyway the sound comes down this audio cable into this computer. We’re just checking the data from last night…”

(Computer keyboard sounds in actuality fades under track.)

The computer has a program that distinguishes the call of the dickcissel from other birdcalls and extraneous noise. The machine records the call, and saves a picture – or spectrogram – of it. Evans trouble shoots his stations and collects data daily. First he winnows out false positives, sounds that tricked the computer, by inspecting the spectrograms.

Evans (to students): “I’m going to set up one folder to put in the dickcissels’ calls and the other I’m going to put in the noise, the false detections. So now I’ve just classified the detections from last night. We had 28 here that we classified as dickcissels…”

After checking the computer and collecting its data the researcher says he has to run. Each of the 15 stations in his network needs a checkup because this weekend might be the climax of the dickcissel migration, bringing a huge flight of birds.

Evans (to students): “…And this weekend we think there are thousands of them just in Northeast Mexico. They’re going to take off. ‘Cause last year in one night, we had over 3,000 detected at McAllen High School…”

In the end, the big flock didn’t appear until the following week. Though the arrival was delayed for several days compared to the previous year, Evans now has proof that by monitoring night calls he can predict the timing and migration route of an individual bird species.

(Sound of truck door closing and truck starting up.)

Walcott: “It’s really an extraordinary accomplishment.”

Cornell professor Charles Walcott says the migration information Evans is discovering can’t be collected any other way. It’s all the more extraordinary because Bill Evans, who once worked for Walcott, has neither a college nor any other degree.

Walcott: “With Bill’s scheme you can now say, well, this was an evening when we had a huge migration of warblers and they were of the following species. And this is very useful and very interesting information. And it gives you a sense of where the migratory paths for each species of birds might be.”

It’s detailed information like this that conservation specialists need to design plans to protect the most threatened species. In the future Evans hopes several large-scale computer networks of the sort he’s testing in Texas will monitor many species throughout the United States. He hopes the listening posts could help solve the mystery of why so many North American species are in decline. This spring, in an important first step, Evans and collaborator Michael O’Brien released a compact disc with night flight calls of most eastern land birds. Now anyone can learn the secrets Bill Evans has unlocked.

For the Great Lakes Radio Consortium, this is Daniel Grossman.

Related Links

Farming With Computers

You probably have a computer in your car, on your desk and maybe even in your stove. It seems like there are computers everywhere these days helping with everything from our checking accounts to our turkey roasts. Now researchers want to install computers in another place, where most of us would least expect it – in Old MacDonald’s tractor. The Great Lakes Radio Consortium’s Daniel Grossman has this story:

Farming With Computers

You probably have a computer in your car, on your desk and
maybe even in your stove. It seems like there are computers everywhere
these days helping with everything from our checking accounts to our
turkey roasts. Now researchers want to install computers in another
place, where most of us would least expect it – in Old MacDonald’s
tractor. The Great Lakes Radio Consortium’s Daniel Grossman has
this story:

Greenhouse Gas Demystified

Last summer, an international team of scientists announced a startling discovery. Writing in the journal Science, the team reported finding a rare gas in Antarctic snow and in the air. The compound has an unusually powerful ability to trap heat in the atmosphere. The paper did not identify the source of the gas, a riddle that puzzled climate researchers worldwide. Now a surprising announcement appears to solve the mystery. The Great Lakes Radio Consortium’s Daniel Grossman has the story: