one decade left

Science now estimates that we have 10 years left to stabilize carbon emissions before we doom the future to serious problems.

Anyone who has taken chemistry is familiar with the principle behind the threat: the volume of a liquid increases with temperature. When the liquid in question is our ocean, each degree rise in temperature adds about 10 centimeters, not enough to drown coastal cities, but enough to speed up beach erosion and expand flood risk zones.

The tides change sea level by as much as 10 meters, and storms can do the same, so the rise from thermal expansion will not be catastrophic but gradual. It will make coastal storms more lethal and destructive.

Compounding the problem is the fact that the sea erodes glaciers and sea ice like it does beaches, and glaciers and sea ice are themselves melting. Sea level rise from the loss of ice also happens on a centimeter scale, but a little faster than thermal expansion, with the added risk of collapses.

If carbon emissions continue to rise, thermal expansion and ice melt will raise sea level enough to flood coastal land. Researchers estimate that the point at which climate change transitions from making weather harsher to being a destructive force of its own is around a two degree Celsius rise in temperature. At that point, the ocean will be a meter higher and big pieces of Louisiana, Florida and Texas will go underwater, plus a lot more land worldwide. So far industrial consumption of fossil fuels has caused a rise of 0.6 degrees.

To preclude catastrophic coastal floods and the loss of cities and towns, global carbon emissions must peak within the next decade and start to decline. Inaction on carbon emissions is becoming a violent, destructive policy.

hunting sandhill cranes

The Tennessee Wildlife Resources Agency is considering a proposal to allow hunting of sandhill cranes and is accepting public comments through January.

This is a good sign in many ways. Nearly extirpated during our country's industrial expansion, these birds have rebounded to healthy population sizes, thanks mainly to the arrest of wetlands destruction. Another crane, the whooping crane, remains on the brink of extinction, but decades of extraordinary effort have restored an eastern migratory population that produced its first wild-born birds in the past couple of years. These critically endangered birds flock with sandhills during migration and on wintering grounds, and this is the prime reason for concern about this proposed hunt.

TWRA has taken steps to reduce the possibility of a whooping crane being accidentally shot, but they should do more. Hunting will not be allowed on Hiwassee Refuge, where the majority of both species congregate during Tennessee stop-overs, and permits will include identification guides to help hunters learn the differences among sandhills, whooping cranes and snow geese. Crane season coincides with the late duck season, primarily the month of December, when whooping cranes will have mostly moved on to their ultimate winter range in Florida.

This is all good, but the fact of the matter is that whooping cranes are closely monitored, and TWRA could suspend hunts while whoopers are present. In materials describing this proposed hunt, TWRA says, "This population of whooping cranes is an experimental flock. TWRA does not propose to stop hunting sandhill cranes if/when whooping cranes migrate through." Dismissing the whooping crane flock as "experimental" is a profound insult to the hundreds of people who have dedicated themselves to rearing and training the flock, a decades-long effort that culminated in teaching the cranes their route by guiding them behind an ultralight plane.

Whooping cranes from the larger Central Flyway population have been shot accidentally, but by goose hunters, not sandhill crane hunters. A few years ago in West Tennessee, the first wild swan seen in Tennessee since Audubon's time was shot by a goose hunter. It takes minimal competence to distinguish a goose from a crane, but goose hunters have not demonstrated even that baseline skill. Perhaps TWRA should aim its educational efforts more toward that larger population of hunters.

Tennessee farmers have been granted depredation permits for sandhill cranes in recent years, but damage to agricultural crops is a minimal problem, if not entirely exaggerated, since cranes arrive after harvests and leave before planting time. Perhaps there are winter crops I am unaware of. Even so, cranes eat insects and mice and may very well earn their share of grains. Damage to crops is a greater problem in the northern states where cranes are present during growing season. Hunting here can benefit northern agricultural interests, but it provides little value to Tennessee farmers.

Sandhill crane meat is reportedly prized for taste and color, and populations can support the proposed take of up to 2199 birds per year. In principle I have no objection to allowing this hunt, but I believe TWRA should do all it can to prevent the accidental death of an endangered whooping crane.

early adopters

If you are trying to learn tree identification, certain times of year are better than others. Right now is the time to learn black gum, sourwood, sumac and tuliptree. These trees get a head start on fall, turning colors while the rest of the trees remain green.

Tulips are turning yellow, the others red. Sumac tends toward fiery tones like you might see in a sunset. It also has compound leaves, and if it has produced fruit, the red, conical berry clusters are distinctive. Sourwood takes on regal tones that approach purple.

Black gum has the purest reds. Gums start losing leaves as soon as its fruit ripens, possibly as a signal to birds to come eat. Migrating thrushes are especially fond of black gum fruits. Leaves begin to turn red in August, but it takes weeks for all the leaves to turn, so there are always a few bright red ones on any tree at any point during fall migration.

Right now, all these trees are recognizable at a glance, so it's a good time for roadside dendrology. As you drive around, you can get a sense for how abundant these species are, where they grow and what is distinct about their growth form. As other trees start to turn, new colors will appear and the roster of trees you have learned to identify will get a bit longer.

milkweeds

Butterfly weed is a native of meadows and clearings. It's rich orange color is among the most spectacular on the Southern Appalachian palette. Because it produces several flower clusters per stalk and they bloom progressively, its hue accentuates our meadows for weeks on end. The plant may even flower twice in good years.

Pollinated flowers turn into okra-like seed pods that break open and release round seeds attached to long, feathery filaments that lift them off on wind gusts. All milkweeds do this, as do many of their relatives. There are 14 species of milkweed known from Tennessee, plus five more in sibling genera. Nationwide, we are home to about a hundred species of milkweed.

Dogbane, another meadow plant, is a close relative, as are persimmons and blueberries. Flowers on that segment of the evolutionary tree tend to be tubular, fleshy and clustered. Seeds are more variable.

Many native pollinators visit butterfly weed flowers, including bees, wasps, beetles, flies and their namesake. Orange butterflies such as monarchs and fritillaries love butterfly weed, whereas tiger swallowtails prefer the pale pink common milkweed often growing nearby.

origin of bird flight

A Nova episode currently in reruns on PBS features bird fossils discovered in China that have shed new light on the origin of flight in birds. Wind tunnel tests on a life-like model suggest a traditional assumption about hip articulation in fossil birds is wrong.

Instead of attaching in a running posture capable of holding the animal's weight, the hind legs attach at a different angle. Researchers call it "splayed" posture, and it is found in crocodiles and other branches of reptile phylogeny. Splayed articulation allows the legs to extend backwards toward the tail, useful for actions like walking on four legs, diving, leaping and gliding.

Running on splayed legs means less power and speed, so the new fossils make the hypothesis that birds evolved flight by being able to run at flight speed and leap into a glide less likely. Part of that hypothesis is the idea that the large middle claw on the hind legs was a "killing claw" thrust at victims using the same power and articulation needed for running. Splay posture suggests other functional possibilities, and the claw may instead have aided in climbing, perching and propelling the protobird from a branch.

Instead of jumping from the ground into flight, the first birds dove into glides from a perch.

There is one more assumption that must be questioned, that protobirds dove into the air. More likely, they dove into water, a more buoyant fluid that creates lift at lower speeds and weaker wing strokes. The fossil record of birds is consistent with a marine origin, with diving birds like loons resembling fossil ancestors more than other modern lineages.

Swimming is easier than flying, and wings likely evolved as swimming appendages before developing the power for airborne flight.

stone free to ride the breeze

This is the shed skin of a stonefly. Aquatic all its life, the insect crawled from Hazel Creek in July, cracked open its thorax, wriggled out, pumped its wings and took flight on misty night air. The white fibers on its head are like an umbilical cord, a remnant connection to the stonefly's former body.

I found the skin on a rock the next morning. It could not have been there long since the rock had been submerged by the prior day's afternoon rain. As the water receded, the stonefly crawled atop and began its brief aerial adulthood.

It will attempt to mate and contribute to the batch of eggs laid in the creek, timed to hatch as autumn leaves drop into the water, bringing nutrients on which the creek's ecosystem depends. Many types of insects and worms live on the rotting organic material that perpetually washes into a mountain stream, and these are prey for crayfish, darters and salamanders, in turn eaten by trout, raccoons and owls.

More than 100 species of stonefly occur in Southern Appalachain waters, with some likely undiscovered, some lost to science at the turn of the last century due to intensive logging, chestnut blight and slaughter of the passenger pigeon. There are more than 1,000 species of stonefly worldwide. Nine families occur in our region. The age of their oldest fossils (about 250 mya) combined with the geological history of the Appalachians makes it quite likely stoneflies evolved in these here hills.

The first winged insects were mayflies, which soon gave rise to damselflies and dragonflies. It was not long after that another mayfly lineage morphed into the first stonefly. All this took place in the Southern Appalachians some 300 million years ago as the shallow, inland sea west of the mountains receded, leaving behind the Cumberland Plateau and finally the Mississippi basin and the grand river herself.

The pictured skin is about an inch long, not counting the tails, and this is about as big as stoneflies get. They resemble roaches, and the similarity is not coincidence. It is likely the roach branch on the tree of life arose from the stonefly limb. In fact, the common ancestor of roaches, crickets and the whole Orthoptera assemblage may have been a stonefly.

Stoneflies spend most of their lives crawling slowly through the stones and muck of a streambed, grazing on crud, shedding occasionally to grow, then one day crawling from the water to sprout wings. Their flight is weak and slow, and they have little ability to manuever. If they run into something, they cling. Their search for a mate is clumsy and fraught with peril, but they have been succeeding for hundreds of millions of years, long enough to diversify into many genera and spawn a major assemblage of terrestrial insects.

to glorify evolution

Evolution is a scientific theory; it explains much of what we observe in the living world. Atomic theory explains observations in chemistry. Gravity explains observations of the cosmos and movements of earth-bound objects. Theories are grand ideas which illuminate and elucidate what we see around us: life, the universe, all that.

Many refuse to see the beauty and truth of evolution, and a common ingredient among adherents of intelligent design, baraminology or other supernatural explanations is a poor appreciation of the diversity of life. This lack of appreciation is understandable. The modern world frees us from worrying which plants are edible, what kind of wood burns best or which insects are truly a threat, so it is easy to become oblivious to the huge variety of plants, trees, insects and life around us.

No naturalist doubts for a moment that life is a grand tableau of evolutionary lineages changing and diversifying. Doubt comes from not realizing how grand the tableau. We can all tell a pine tree from an oak, but if your curiosity stops there, can you be expected to understand the evolution of flowering plants?

Fortunately, it is not necessary to know every pine tree or moth in order to appreciate life's diversity. Knowing the basic parameters -- about a dozen pines occur naturally in our region a thousand or more moths -- is adequate, or at least a good start. An understanding of biodiversity fosters stewardship and wisdom.

Just as gravity explains Earth's trajectory around the Sun, evolution explains the diversity of life. To appreciate evolution, you must first appreciate what needs to be explained, and that is biodiversity. Plants, fungi, microorganisms, mammals, spiders, birds, insects; evolution explains them all.


Intelligent design and other flavors of creationism explain nothing. They push diversity into the unknowable and render planetary history and the tableau of life an incoherent mess. That is unacceptable. Evolution has no competing theories because nothing else comes close to explaining as much about life as evolutionary theory does.

I have decided a running theme of this blog should be the diversity around us. Southern Appalachian forests are a good classroom for learning what evolution explains. Our mountain's age corresponds to the earliest emergence of terrestrial life, plant and animal, so local natural history encompasses events like the origin of flowering plants, insect flight, mammals, birds and the rise and fall of dinosaurs. Much can be learned from the patterns of diversity around us.

another year of unsustainable emissions

The cowardly era of United States history enters its third decade. This week the U.S. Senate opted not to pursue long-overdue climate controls in favor of an easy cop out: tightening offshore drilling limits.

Never mind that funding for regulators, a purge of corrupt Bush appointees and hires and the market demise of BP is all that is needed to prevent future Deepwater Horizon disasters, the Senate's decision not to control carbon emissions is perverse regardless of its excuses. Top its cowardice off with the death of Stephen Schneider and a federal court's reversal of North Carolina's win over TVA and you have the worst week in air pollution history since the discovery of Appalachian oil.

Schneider was a truth teller who not only understood the science of carbon gases, but also why people have trouble understanding global warming. He stressed the clear and present danger of rising gas concentrations. He died July 18 on a plane to London. Rather than honor his memory, the U.S. Senate chose to spit on science and continue free abuse of the atmosphere as an emissions dump. The cowardly era remains entrenched despite Obama's plain mandate for change.

The U.S. Fourth District overturned a federal indictment against TVA because it claimed nuisance laws, rather than decade-old Clean Air Act deadlines constituted the force of North Carolina's argument. The court said "the injunction would encourage courts to use vague public nuisance standards to scuttle the nation's carefully created" clean-air laws, so TVA need not obey those carefully created laws. Such logic is the hallmark of corporate ownership of government.

Our Senate is desperate for funds to cover its gross bailout of investment firms. Taxes on carbon emissions, lucrative even at rates imperceptible to consumers, could help offset the damage inflicted when Congress repealed Glass-Steagall in 1999 and set the stage for the current economic collapse, but the Senate lacks courage to pass even a trivial tax on a dangerous practice.

Sustainable emissions are the easiest to accomplish and first necessary goal in a transition to a sustainable economy, but the U.S. Senate and the corporations that own it have no interest in a sustainable future for the United States or the planet. Sustainable futures do not maximize profits nor garner huge executive bonuses.

A truly democratic government would tax elite earnings and pollution; our Senate will not.

Rockhouse flowers

The Cumberland Plateau is home to many unusual plants. A seafloor when the Appalachian mountains were younger and taller, the plateau's geology is distinct, but its forests are similar to Appalachian forests. Where the plateau's geological youth is most apparent -- at the eroding rim of the gorge and in the dynamic river channel -- the unique conditions posed an evolutionary opportunity.

Plants that took advantage of that opportunity diverged from their Appalachian ancestors. Numerous species are known only from the Cumberlands. Some of these are found on the river shoals, others in the rockhouses along the rim, like the pictured catchfly. A close relative of fire pink, roundleaf catchfly (Silene rotundifolia) grows only on rock faces in the Cumberlands.

A rockhouse is a cliff that has eroded beyond vertical, creating an overhang and a sheltered space below. These sheltered areas may be large enough for a camp. Some like Hazard Cave in Pickett State Park are large enough for a village. The floor of a rockhouse is sandy, offering a dry, soft place to sleep, and the sloping rock face carries smoke from a fire up and away. Native Americans used rockhouses for shelter, but they considered the Cumberlands dangerous and cursed, so these camps were temporary stopovers during hunting or trading excursions and never as elaborate as cliff dwellings in southwestern states.

To protect endemic plants and animals, camping in rockhouses is now forbidden. One of the most vulnerable endemics is the Cumberland sandwort (Minuartia cumberlandensis), a lacy plant that lines the edges of rockhouse floors, living off what little moisture flows down the rock or blows in during rains. Roundleaf catchfly grows higher up in nooks etched into the sandstone, so it can not be trampled, but heat and smoke from a fire could harm it. Mountain spleenwort (Asplenium montanum), a fern, likes the same sort of nooks as roundleaf catchfly.

In the drip zone along the mouth of a rockhouse you can find lady fern, sedges and rockhouse featherbells (Stenanthium diffusum), a rare lily only recently recognized as a species. University of Tennessee botanist Gene Wofford realized the plant he kept finding in the Cumberland plateau was different than eastern featherbells (Stenanthium gramineum). He published his findings and a new endemic was born to science.

These plants grow happily in a rockhouse's unusual habitat, but how they get there in the first place is a bit of a puzzle. Sandstone in a rockhouse often appears crusted, with a harder layer above eroding more slowly than the rock below. These crusts are curved and irregular, not stratified like typical rock layers.

On my most recent visit to the Cumberlands, a botanist explained how those crusts form. It is a present-day phenomenon, not a trace of an ancient process. Just as tree roots stabilize a riverbank, mosses and lichens protect sandstone from erosion. In particular they slow the impact of winds. On a still day it is hard to imagine what a wind could do when it hits a rockhouse, but if you get caught in one during a storm or just put your imagination to work, you can see the sand at the base of the rock wall kicking up or rain and debris blowing in to knock grains from exposed sandstone.

Those same winds can cast a small seed onto a ledge evolution made its ideal home. Those same winds are what carves a rockhouse from a cliff in the first place. Where winds in the gorge tend to collect and swirl is where rockhouses form, so what looks like shelter from a storm can actually concentrate its power. No wonder native Americans preferred to live elsewhere.

upriver from Nashville

The same storms that flooded Nashville filled the banks of Big South Fork, the major eastern tributary of the Cumberland River. Most of the rocks in this photograph were submerged during the flood, and their surfaces were scoured of soil. Riverbank plant communities took a hit, but these plants are adapted to floods and should rebound before rains that improbable strike again.

Yesterday along Big South Fork, recently deposited debris marked high waters 20 feet above current flow. Tree trunks were submerged at the edge of the gorge's forest, but not much evidence of uprootings or other damage was apparent. Among the rocks along the bank, alders, viburnums, birches, sycamores and other woody plants remained firmly rooted and full of leaves. Royal ferns were abundant; what was missing were last year's fronds.

When this river flooded last month, plants along its banks would have been flush with tender new growth. Shrubs and saplings may have lost leaves, and smaller herbaceous plants may have lost all their above-ground growth. Trees above flood stage had maturing, waxy leaves while those in the river had newer leaves.

Judging from what the riverbank looks like a month later, I would guess the early May flood stripped leaf litter, fresh growth and topsoil, but was not strong enough to cause major damage. Rainfall totals east and north of Nashville were not as epic. An epic Big South Fork storm would tumble most rocks in the photograph a bit further downriver and completely reset riverbank ecosystems.

One plant that may have suffered setbacks in the flood is the Cumberland rosemary, one of several endangered or threatened species found only in the Cumberland and Emory river systems. Yesterday I had the privilege of accompanying professional botanists on a search for rare and endemic plants, and we checked two known populations of rosemary. One population was but a dozen plants in a small span of a large boulder field. The second was not found; we may have misunderstood our map. My guess is the rosemary and other smaller plants got a setback that will limit this year's seed set, but they will recover within a year or three.

cranefly siesta

Craneflies fly at night and seek shade during the day. Many begin life in streams and ponds as long, fat, white worms, and their physiology is geared toward cool and damp.

This orange species sought perch inside a cluster of Virginia creeper leaves, refuge from the sun all afternoon until evening light crept in.

In damp Southern Appalachia, craneflies are among the most speciose insects, coming in a variety of sizes and patterns. Few are as colorful as the one in the photo, but some have black markings on their wings or abdomen that add a bit of flair. Most are weak fliers, slow and drifting, with their long legs serving as bumpers and feelers.

Sometimes called mosquito hawks or mistaken for mosquitoes, crane flies have tiny, weak mouthparts used primarily to slurp water. Their long abdomen is a storehouse of fats eaten during wormhood, so they have little or no need to eat in adult form and are harmless to man and mosquito alike.

yard week

Despite a vigorous spring for the native flora and fauna, bird migration has been slow this year. Not just me but many Southern Appalachian birders report late arrivals and low numbers of warblers and the rest of the lot that winters in the tropics. This week things picked up.

An indigo bunting set up a territory in the front yard, joining the thrasher and field sparrow already raising families in the unmowed scrub. A Cape May warbler and blackpoll sang during a brief feeding stopover, and male grackles displayed amid tuliptree flowers.

I saw something I had never seen before, a traveling flock of kingbirds, and I added gray-cheeked thrush to my life list, though I've seen them in fall several times. Finally I got not only a good look but a chance to hear it sing, go inside to listen to minimus and bicknelli, then hear it sing some more. Check.

I am close enough to a river that I get flyovers by swallows, waterfowl and other riparian birds, so when I spotted a kingbird flying above the trees I was pleased, but not surprised to add eastern kingbird to my yard list. Later I saw first one, then three, then six, ten kingbirds hopping around the treetops. Not only have I never seen a kingbird in my yard, I have never seen them in a flock.

A cedar waxwing flock busied itself gobbling pollen from tuliptrees, while tent caterpillars gobbled the first flush of leaves from black cherries. These caterpillars will not eat the flowers, already fertilized, so the tree will grow new leaves and produce a full crop of fruit by August. It is an agreement between insect and tree which also worked out well for the female tanager gorging herself on caterpillars in the small cherry near my front porch.

It has at least five tents in it, and the caterpillars will eat it bare. Once they have eaten all the leaves, the caterpillars will pupate into a good-sized moth that looks like this. A brood of scarlet tanagers and a flight of brown fuzzies will grow from the cherry tree's sacrifice.

It is tempting to ignore chickadees this time of year in favor of passersby and gladyrbacks, but I watched one long enough to notice it was only visiting the dead tips of oak twigs where wind had ripped leaves or limbs out. It was finding caterpillars, a different species, taking refuge from the afternoon sun. About every third twig the bird checked it swallowed a worm.

A chickadee I saw later in a hickory hopped from one just-opening leaf cluster to another, having similar luck with yet another species of baby moth.

bald-faced hornets

Yesterday I saw my first and second bald-faced hornets of the year but did not get a photo. They were queens looking for a good place to construct a nest. That might seem like something to discourage, possibly even grounds for extermination, but this is our only native hornet, so I tend to cheer for them.

Years of encounters with stinging insects have lead me to be comfortable around them. They will sting ruthlessly if you get near their nest, but outside that danger zone of a couple square yards, they will not sting unless provoked. Unfortunately, many people's reaction is just that: swat, flail and freak out. If human stupidity were met with painful stings more often, the world would be a better place. Perhaps it's a bit misanthropic, but I'm on the side of wasps and hornets and against stupidity.

This is the time of year when being diligent and observant pays off. Inspect your porches and outbuildings for nests now. Early morning is a good time for inspection since wasps fly poorly when they are cold. If you can find nascent nests before the founding queen has hatched her first brood of workers, extermination can be achieved with minimal risk to you or the insect. Once that first brood hatches, there is almost always a sentinel on guard. When it's just the founding queen, she'll be away from the nest often, and when she is, knock it down. When she returns and finds her work destroyed, she will most likely take up her mission elsewhere rather than rebuilding in a cursed location.

Why might you want wasps and hornets around? They are nature's janitors. They spend most of their time hunting for dead insects and animals, which they feed to their larvae. Despite their aggressiveness toward intruders, they are not predators, just opportunists. Adult wasps and hornets feed mostly on nectar, saving richer meals for their brood, so they work a little pollination duty into their routine.

If you are going to get stung by these social insects, it will likely be from wandering too close to a nest you did not know existed. Nests up in a tree or near the peak of your roof are not a danger. If feel safest when I know where the nests are, so I go on inspection runs now when it is easy to respond. Sometimes I choose to let the nest be, knowing I can avoid it. One year bald-faced hornets nested under the awning of a window that is painted shut. It was perfect. I could safely watch them from inside. One day I came home to find the nest in ruins. The summer tanagers, known locally as "bee birds," had found the hornets and made a meal of them.

You might want to keep them around as tanager food.