A cheerful Biology Comic?!
Dooryard Views
Watching from my dooryard I think the local raptor population is increasing. I see more and more small birdeating hawks: sharpshins (a small short winged forest hawk), cooper’s hawks (a larger edition of the same), merlins (a tiny forest falcon, the size of a robin).
Three or four autumns ago I watched an immature Cooper’s hawk perched in the top of a dead aspen in my meadow for an hour. If it hadn’t perched there so long (preening and ruffling its feathers) I wouldn’t have been able to identify it: separating sharpshins and Cooper’s hawks is difficult.
Several times a summer a sharpshin arcs over the yard. If one stands and looks up on a sunny September day with a north wind, one sees them soaring south, flicking their wings like butterflies, among the stately redtails.
The call of our common summer hawk, the broadwing, still drops from the sky on sunny days.
A friend found a Cooper’s hawk nest a few weeks ago in a red pine beside a busy mountain trail. Going to look for the nest, I happened upon the hawk perched in a dead elm next to an abandoned beaver pond. A bronzed grackle was perched in the same tree. Upright and gray, larger than the grackle, the hawk stared straight ahead. Neither bird was moving. Perhaps the hawk wasn’t hungry. The safest thing for the grackle (who glanced at the hawk from time to time) was not to fly.
And so what?
Well such hawks, like the fisheating American mergansers that have become common on the river, occupy the top of the food chain. They eat migratory birds and migrate themselves. Thus they concentrate pollutants (absorbed by the birds with their insect prey) from all over. That, plus shooting during migrations (when they are most vulnerable), is thought to be reason for their enormous decline in the middle part of the last century.
So their increase is a good thing: shooting has stopped; the chemicals that worst affected them are declining in the environment (though many bad boys, including mercury, are rising). Of course their prey species (songbirds) have also been declining.
A good thing in more than one way: raptors (day flying hawks) sculpt their surroundings. Cowbirds are a nest parasite from the prairies. Cowbirds spread east during the last century (clearing the eastern forests for farmland created an eastern prairie habitat for them) and increased in number tremendously. The female cowbird lays its egg in the nests of small songbirds (such as warblers and thrushes). The egg isn’t recognized as foreign by the parents. The young cowbird hatches out quickly, grows quickly and pushes the other hatchlings out of the nest. A warbler raises a cowbird chick several times its size.
A female cowbird will parasitize several nests – nice work if you can get it. So some warblers, wood thrushes and other neotropical migrants have been declining. (There are additional causes for this but abundant cowbirds are a factor.)
Since the 1970s, at least one male cowbird has perched in my apple tree gurgling its liquid notes all spring. Often two females accompany him. This year I saw one once, briefly. Their habit of sitting in a treetop displaying makes them vulnerable to our bright eyed hawks.
Perhaps as a result I have heard wood thrushes singing near the house the last two summers for the first time in 30 years. (But mercury accumulating in the insects of the forest floor also affects wood thrushes, as well as habitat change in the tropical forests where they winter.)
So fewer cowbirds (or scared cowbirds) are a good thing. I see also fewer blue jays. The beautiful blue jay (illuminations in blue and violet) is a nest predator. I once watched a blue jay go from nest to nest in the carved stonework above the doorway of a church, plucking out baby sparrows, one from each nest, while the parents chirped and squawked nearby. What could they do?
Sharpshins enjoy tasty blue jays, though the jays are slightly larger than they. One winter afternoon I watched a sharpie out my window eat the breast meat off a jay too large for it to carry away. Jays eat at feeders and the hawks (not stupid) cruise from feeder to feeder. As the hawk fed, the movements of the jay’s spread wings became feebler and feebler. Finally the little hawk flew off with the still remains through the woods.
So this is good. Though the merlins and the sharpshins will undoubtedly also strike at the indigo bunting that now sings in the dead aspen, the scarlet tanager singing in the pines, the crested flycatcher that whoops from the woods.
That’s how it is! In a better world than ours all these birds would be much more numerous, eat the insects that eat the trees and produce many many young.
Saturday, June 26, 2010
Tuesday, June 8, 2010
Biology Comics
Oily Dreams: the Deepwater Horizon Disaster
The well drilled by the drilling ship Deepwater Horizon in a mile of water continues to pour oil and gas into the deep sea. Some of the oil floats to the surface, where the lighter fractions evaporate (up to half the oil), the rest floats in rafts on the sea, until driven by winds and currents onto the beaches and marshlands of the gulf coast. Turtles or whales that swim through the oil become disoriented; some die. Birds that land in it die. The film of oil kills the larvae of fish and crustaceans that float in the spring waters of the gulf; including the larvae of such long distance swimmers as the western Atlantic population of the bluefin tuna.
Much of the oil and gas disperses underwater to form deep plumes of tiny droplets under the sea surface, that oxidize, or are oxidized by bacteria, and use up the oxygen in the water. The water in the plumes may become too depleted of oxygen for animals to survive. Such plumes are also toxic to the larvae of gulf animals and to the animals (deepwater corals, fish, crustaceans) themselves.
Some summer anoxia in coastal bays and estuaries (like those of the gulf) is normal. The upper layer of the ocean is ventilated by storms mixing surface water, rich in oxygen, with the waters below. Oxygen also diffuses downward into the water column, but slowly. Currents bring deeper waters to the surface, renewing their nutrients and being renewed with oxygen.
In summer storms are fewer. The sun heats the surface waters, which tend to form a lid over the colder waters below. The water column stratifies. Fresh water from rivers pouring into the sea, less dense than salty ocean water, also sits on the sea’s surface, helping keep the lid in place. So the oxygen content of the deeper waters falls.
If the water’s oxygen content falls too low, fish and benthic organisms (corals, anemones, worms, sponges) suffocate. One July evening in 1987, lobsters started crawling out of Long Island Sound onto shore: insufficient oxygen was left in the water. Bluefish gasped in the shallows. Modern summer anoxias are made more extreme by the nutrients (from sewage effluent, pet poop, burning fuel, fertilizer) we put in the ocean. These materials cause algae to grow. The algae grow and die, sink to the bottom of the sea and decay, using up the available oxygen. (This process also sequesters carbon.)
Fertilizer from farms and lawns running off into the Mississippi River has created a so-called dead zone of anoxic water in the Gulf of Mexico for several decades. The size of the zone increased dramatically after the 1993 floods, which increased the runoff of nitrogen and pesticides into the gulf. It continues to grow.
I would guess its growth is related to the size of the American corn crop. The nitrogen runoff is caused by poor agricultural practice in the Mississippi basin: not rotating corn and sod crops; applying too much fertilizer; putting too much land in crops, period. Fertilizing the tens of millions of acres of suburban lawn grasses in the Mississippi basin also adds nitrogen. Rotating cornland into hays would reduce the size of the corn crop by a third and help heal the river and the gulf. With the price of corn so low, people burn it instead of wood and transform it into a motor fuel; but corn is a food. Even agricultural economists say we have too much corn.
The nutrients and soil running off poorly managed farms also degrade rivers, and their fisheries.
So the anoxia caused by the oil adds to the anoxia caused by foolish agricultural policies in the fertile center of the continent.
The rafts of evaporating oil also drift into the marshes at the mouth of the Mississippi and onto coastal beaches.
On the beaches it is removed. (Some sinks below the surface.) Removing it from marshes is more difficult.
Thousands of people have been organized to remove the oil. They drive vehicles through colonies of nesting birds and over low coastal dunes, flattening them. They walk through pelican nests (whose adults will die anyway).
Some biologists say it would be better to leave the oil alone. Over time most of it (perhaps 70%) will evaporate or biodegrade. In Prince William Sound in Alaska, high pressure washing with warm water of rocks along the shore after the Exxon Valdez spill drove the oil underground, where it remains, mobilized from time to time by digging animals or rock shifting storms. (Once out of reach of oxygen oil breaks down extremely slowly. Adding nutrients like nitrogen may help.) The herring fishery in the sound never recovered and other fisheries remain much reduced many years after the spill. Fish living near a 40 year old spill on Cape Cod show elevated levels of liver enzymes many years later. (Fuel oil there also remains under the surface of the beaches, driven down by gravity and storms.) No one knows the continuing effects on fish eggs and larvae and thus on fish abundance; but our use of oil is a sort of tax on the wild world. Oil on the surface of the ocean or land will eventually be broken down by bacteria and archaea (natural asphalt lakes are full of life) but in the case of heavy tarry oils eventually is a long time.
Oil and gas seeps in the gulf may release a million barrels a year (not a small amount). This oil is used by bacteria, which are eaten by large worms and other creatures in so-called dark ecosystems on the seafloor. (‘Dark’ because they are out of the reach of sunlight.) So oil is not new to the gulf.
Booms are used to keep the oil from reaching the beach and people scoop up and bag the oil that does. Hair (human and otherwise) makes an excellent absorbent and afterwards the oil soaked material can be burned. Behind the booms, skimmers remove the oil from the surface of the sea.
Booms and sleeves stuffed with hair are cheap but oil companies don’t want to pay for buying and storing the material against emergencies. (Renting the drilling ship Deepwater Horizon cost about $500,000 a day.) Absorbent booms are probably better than plastic ones but are more expensive.
Any cleanup is a big mess. Nothing really works. Storms and waves cause problems. Marsh vegetation will come back after one oiling but several oilings will kill it, leaving the marshland open to erosion by the sea.
But gulf marshlands have been receding for decades, a matter that is well known. Modern levees keep the muddy waters of the Mississippi from flowing over the marshlands and rebuilding them. Rather, the river water is sent straight out into the gulf, where its muds and fertilizers add to the dead zone, rather than fertilize and maintain the protective marshlands of the delta.
Canals dug by oil companies through the marshes (10,000 miles of them) let the sea in to erode the marshes.
Salt water penetrates inland and as the marshes become more saline, their vegetation changes. They become less desirable to migratory waterfowl. Cypresses and other trees die.
The receding marshlands expose the coast to storms.
The Caribbean, of which the Gulf of Mexico is part, once had tens of millions of sea turtles grazing its seagrass meadows and coral reefs, manatees nibbling seagrasses along its coasts, seals eating its forage fish and many whales. Its spawning fish came from nearby and far away. Like the water birds most of these animals are reduced by 90-95% from their original abundance. Some losses were deliberate (turtles and manatees were hunted for food and oil), some a consequence of human settlement.
The Ixtoc spill of 1979-80 in the Mexican section of the gulf, released 10,000-30,000 barrels a day for ten months until contained. Much of the oil ended up on Texas beaches. The Deepwater Horizon spill is putting out 25,000-60,000 barrels a day. If the relief wells work and end the spill by August, it will only have lasted half as long. (The Ixtoc relief wells did not work at first.)
As of June 5th a temporary containment system seems to be capturing half the oil.
Such oil spills are only a part of our mismanagement of the ecosystems of the gulf. The Louisiana sport and commercial fisheries are worth about 8 billion dollars a year. In general, we have no idea of our place amidst the natural systems of the planet.
And as long as we place no value on nature, we will treat it like shit.
The well drilled by the drilling ship Deepwater Horizon in a mile of water continues to pour oil and gas into the deep sea. Some of the oil floats to the surface, where the lighter fractions evaporate (up to half the oil), the rest floats in rafts on the sea, until driven by winds and currents onto the beaches and marshlands of the gulf coast. Turtles or whales that swim through the oil become disoriented; some die. Birds that land in it die. The film of oil kills the larvae of fish and crustaceans that float in the spring waters of the gulf; including the larvae of such long distance swimmers as the western Atlantic population of the bluefin tuna.
Much of the oil and gas disperses underwater to form deep plumes of tiny droplets under the sea surface, that oxidize, or are oxidized by bacteria, and use up the oxygen in the water. The water in the plumes may become too depleted of oxygen for animals to survive. Such plumes are also toxic to the larvae of gulf animals and to the animals (deepwater corals, fish, crustaceans) themselves.
Some summer anoxia in coastal bays and estuaries (like those of the gulf) is normal. The upper layer of the ocean is ventilated by storms mixing surface water, rich in oxygen, with the waters below. Oxygen also diffuses downward into the water column, but slowly. Currents bring deeper waters to the surface, renewing their nutrients and being renewed with oxygen.
In summer storms are fewer. The sun heats the surface waters, which tend to form a lid over the colder waters below. The water column stratifies. Fresh water from rivers pouring into the sea, less dense than salty ocean water, also sits on the sea’s surface, helping keep the lid in place. So the oxygen content of the deeper waters falls.
If the water’s oxygen content falls too low, fish and benthic organisms (corals, anemones, worms, sponges) suffocate. One July evening in 1987, lobsters started crawling out of Long Island Sound onto shore: insufficient oxygen was left in the water. Bluefish gasped in the shallows. Modern summer anoxias are made more extreme by the nutrients (from sewage effluent, pet poop, burning fuel, fertilizer) we put in the ocean. These materials cause algae to grow. The algae grow and die, sink to the bottom of the sea and decay, using up the available oxygen. (This process also sequesters carbon.)
Fertilizer from farms and lawns running off into the Mississippi River has created a so-called dead zone of anoxic water in the Gulf of Mexico for several decades. The size of the zone increased dramatically after the 1993 floods, which increased the runoff of nitrogen and pesticides into the gulf. It continues to grow.
I would guess its growth is related to the size of the American corn crop. The nitrogen runoff is caused by poor agricultural practice in the Mississippi basin: not rotating corn and sod crops; applying too much fertilizer; putting too much land in crops, period. Fertilizing the tens of millions of acres of suburban lawn grasses in the Mississippi basin also adds nitrogen. Rotating cornland into hays would reduce the size of the corn crop by a third and help heal the river and the gulf. With the price of corn so low, people burn it instead of wood and transform it into a motor fuel; but corn is a food. Even agricultural economists say we have too much corn.
The nutrients and soil running off poorly managed farms also degrade rivers, and their fisheries.
So the anoxia caused by the oil adds to the anoxia caused by foolish agricultural policies in the fertile center of the continent.
The rafts of evaporating oil also drift into the marshes at the mouth of the Mississippi and onto coastal beaches.
On the beaches it is removed. (Some sinks below the surface.) Removing it from marshes is more difficult.
Thousands of people have been organized to remove the oil. They drive vehicles through colonies of nesting birds and over low coastal dunes, flattening them. They walk through pelican nests (whose adults will die anyway).
Some biologists say it would be better to leave the oil alone. Over time most of it (perhaps 70%) will evaporate or biodegrade. In Prince William Sound in Alaska, high pressure washing with warm water of rocks along the shore after the Exxon Valdez spill drove the oil underground, where it remains, mobilized from time to time by digging animals or rock shifting storms. (Once out of reach of oxygen oil breaks down extremely slowly. Adding nutrients like nitrogen may help.) The herring fishery in the sound never recovered and other fisheries remain much reduced many years after the spill. Fish living near a 40 year old spill on Cape Cod show elevated levels of liver enzymes many years later. (Fuel oil there also remains under the surface of the beaches, driven down by gravity and storms.) No one knows the continuing effects on fish eggs and larvae and thus on fish abundance; but our use of oil is a sort of tax on the wild world. Oil on the surface of the ocean or land will eventually be broken down by bacteria and archaea (natural asphalt lakes are full of life) but in the case of heavy tarry oils eventually is a long time.
Oil and gas seeps in the gulf may release a million barrels a year (not a small amount). This oil is used by bacteria, which are eaten by large worms and other creatures in so-called dark ecosystems on the seafloor. (‘Dark’ because they are out of the reach of sunlight.) So oil is not new to the gulf.
Booms are used to keep the oil from reaching the beach and people scoop up and bag the oil that does. Hair (human and otherwise) makes an excellent absorbent and afterwards the oil soaked material can be burned. Behind the booms, skimmers remove the oil from the surface of the sea.
Booms and sleeves stuffed with hair are cheap but oil companies don’t want to pay for buying and storing the material against emergencies. (Renting the drilling ship Deepwater Horizon cost about $500,000 a day.) Absorbent booms are probably better than plastic ones but are more expensive.
Any cleanup is a big mess. Nothing really works. Storms and waves cause problems. Marsh vegetation will come back after one oiling but several oilings will kill it, leaving the marshland open to erosion by the sea.
But gulf marshlands have been receding for decades, a matter that is well known. Modern levees keep the muddy waters of the Mississippi from flowing over the marshlands and rebuilding them. Rather, the river water is sent straight out into the gulf, where its muds and fertilizers add to the dead zone, rather than fertilize and maintain the protective marshlands of the delta.
Canals dug by oil companies through the marshes (10,000 miles of them) let the sea in to erode the marshes.
Salt water penetrates inland and as the marshes become more saline, their vegetation changes. They become less desirable to migratory waterfowl. Cypresses and other trees die.
The receding marshlands expose the coast to storms.
The Caribbean, of which the Gulf of Mexico is part, once had tens of millions of sea turtles grazing its seagrass meadows and coral reefs, manatees nibbling seagrasses along its coasts, seals eating its forage fish and many whales. Its spawning fish came from nearby and far away. Like the water birds most of these animals are reduced by 90-95% from their original abundance. Some losses were deliberate (turtles and manatees were hunted for food and oil), some a consequence of human settlement.
The Ixtoc spill of 1979-80 in the Mexican section of the gulf, released 10,000-30,000 barrels a day for ten months until contained. Much of the oil ended up on Texas beaches. The Deepwater Horizon spill is putting out 25,000-60,000 barrels a day. If the relief wells work and end the spill by August, it will only have lasted half as long. (The Ixtoc relief wells did not work at first.)
As of June 5th a temporary containment system seems to be capturing half the oil.
Such oil spills are only a part of our mismanagement of the ecosystems of the gulf. The Louisiana sport and commercial fisheries are worth about 8 billion dollars a year. In general, we have no idea of our place amidst the natural systems of the planet.
And as long as we place no value on nature, we will treat it like shit.
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