Friday, August 31, 2007

The Fiddlers

Late summer is the season of Orthopterans (crickets, grasshoppers, katydids and locusts). Named for their straight, hardened forewings, these insects are best known for their jumping ability and for the scratchy "song" that the males deliver; the latter is produced by rubbing their legs or wings together and is used to attract females. Grasshoppers and locusts are diurnal fiddlers while crickets and katydids do most of their courting on cool, late summer nights; the song of the katydid is often heralded as the first sign of autumn.

Orthopterans are among the 15% of insects that undergo partial metamorphosis. The eggs hatch into nymphs, which are small, wingless versions of the adult; several molts (over weeks to months) lead to the adult form, bypassing the pupal stage. The eggs are deposited on vegetation or directly on the ground; in the Temperate Zone, most Orthopterans overwinter in the egg stage and, those not eaten by birds, mice or shrews, hatch in the spring. Primarily herbivorous, these insects (especially the grasshoppers and locusts) can cause significant damage in agricultural areas. Their natural predators include kestrels, screech and burrowing owls, crows, jays, magpies, gulls, frogs, toads, snakes and a variety of small mammals; many human cultures also consume these long-legged insects.

Having evolved back in the Carboniferous Period, some 300 million years ago, there are now over 20,000 species of Orthopterans across the globe; most of these live in the Tropics and about 1200 species inhabit North America.

Thursday, August 30, 2007

The Green Line

On land, photosynthetic plants form the base of the food chain, trapping the sun's energy and passing it along to a web of primary and secondary consumers. So too, in shallow seas and in the upper layer of the deep oceans, a wide variety of marine plants, from tiny phytoplankton to giant kelp, support a fabulous diversity of sealife.

But at depths below 450 feet, the solar radiation is too weak to allow photosynthesis and, below this "green line," living plants do not exist. All life in the deep, dark ocean waters is bacterial or animal, sustaining itself in a variety of ways. Much of the food arrives as an endless "snowfall" of animal and plant debris from the upper ocean waters, including occasional windfalls such as dead sharks and whales. Many deep ocean inhabitants supplement this diet by nightly trips to the rich surface waters where, under cover of darkness, they feed on phytoplankton, krill and other small organisms. Of course, secondary consumers of the deep ocean sustain themselves by feeding on the smaller fish and invertebrates that inhabit their realm.

Along the mid ocean ridges, where ocean crust is forming, colonies of bacteria feed on hydrogen sulfide that spews from the hot, volcanic vents. These, in turn, support an amazing diversity of exotic creatures, most of which are not yet known to science. In similar fashion, other bacteria feed on methane that seeps from the ocean floor at many locations across the globe; these bacteria also form the base for a web of sealife, adapted to their unique environment.
We humans are just beginning to explore the mysteries of the deep, dark ocean, the largest ecosystem on Earth and the least understood.

Wednesday, August 29, 2007

Humans and Stress

As a physician, I am well aware that humans are prone to stress and that many of our maladies are closely linked to this complex phenomenon. Mediated by a network of psychological, neurologic and endocrine factors, chronic stress has been associated with cardiovascular disease, hypertension, tension headaches, muscular pain, peptic ulcers, irritable bowel syndrome, anxiety, depression and chronic fatigue. Though stress is part of life and cannot be totally avoided, there are ways to reduce and manage this health risk; I suggest the following measures:
1. Most stress develops when we feel overwhelmed with respon-sibilities. Make a list of projects or duties at the beginning of each week and plan to complete one (and only one) each day; this controls the demand that you place on yourself.
2. Choose an aerobic exercise that you enjoy (walking, hiking, biking etc.) and commit at least 45 minutes to this activity each day. Exercise is an excellent way to diffuse stress; however, don't bring your cell phone or friend along (a daily period of solitude is essential).
3. Listen to the music of your choice at least 1 hour each day; this can be combined with reading, paperwork, hobbies or other household chores if necessary. The therapeutic effects of music are inherent to the human species.
4. Obtain your news from the print media or stations such as NPR, PBS or the BBC; most cable news programs and radio talk shows inject an excessive degree of stress into our lives with their intensity, sensationalism and confrontational style. Listening to others argue about political or social issues is an unnecessary source of stress.
5. Make sure to get adequate sleep; while this need seems to vary among individuals, 7-8 hours is a good target. Avoid excessive caffeine or alcohol intake, since these agents often interfere with sleep.
6. Finally, eliminate sources of chronic stress over which you have no control. If all reasonable interventions fail to correct the problem(s), more drastic measures (such as changing jobs or ending a relationship) may be necessary to protect your own health.

Tuesday, August 28, 2007

Dean visits the Southwest

After coming ashore last week, Hurricane Dean moved into central Mexico and has since reignited the Southwest Monsoon. Injecting copious tropical moisture into the region, the storm can now be blamed for floods in Las Vegas and a soggy week in Albuquerque.

Of course, the remnants of Dean are only part of the explanation for a resurgence of the monsoon rains. A low pressure "disturbance" off southern California, coupled with the persistent dome of high pressure over the lower Mississippi Valley, are producing southerly winds over northern Mexico and the Four Corners region, pushing the moisture northward. In addition, a cold front has moved into Colorado from the northwest and southwest winds ahead of the front are bringing Dean's gift to the southern Rockies and Front Range cities.

Though hurricanes often devastate coastal areas and spawn destructive inland tornados, they can also bring beneficial rains to drought-plagued regions. Pros and cons can be listed for all of nature's forces; we tend to judge them based on how they affect our personal lives.

Sunday, August 26, 2007

The Central Lowlands

Heading back to Missouri, we entered the Central Lowlands of North America along I-71, between Mansfield and Columbus, Ohio. This vast geophysical province stretches from central Ohio to the eastern Dakotas and from northern Kentucky to the prairielands of Central Canada. To the east, it is bordered by the edge of the Appalachian Plateau while, to the south, it abuts the low plateaus and Shawnee Hills of central Kentucky, southern Indiana and southern Illinois; further west, the southern edge of the Central Lowlands runs along the Ozarks of Missouri and extreme southeastern Kansas. The western extent of the Province is defined by the High Plains escarpments of Kansas, Nebraska and the Dakotas while the Great Lakes, the Canadian Shield and the great Northwoods form its northern boundary.

Underlain with Paleozoic sedimentary rocks, most of the Central Lowlands was plowed flat by the Pleistocene Glaciers and, in these regions, its soil was enriched with glacial till. When white settlers first crossed the Appalachians, a sea of tallgrass prairie covered the Province, home to huge herds of bison. Forest, primarily limited to the stream channels, was kept at bay by high winds, periodic drought, wildfires and the grazing and trampling of the bison themselves. Soon, the bison were decimated and the prairie was plowed, yielding the North American Corn Belt that we see today.

Following I-70 from Columbus, Ohio, to Columbia, Missouri, travelers encounter a gently rolling landscape, covered by croplands and hay fields. Away from the cities and towns, woodlands are still clustered along the streams and rivers, whose valleys provide the only significant topographic relief. While vital to our economy and home to a diverse collection of natural habitats, the Central Lowlands is certainly not the most scenic province for human travelers; but to migrant waterfowl, its lakes, rivers, wetlands and grainfields must look like paradise.

Saturday, August 25, 2007

The Flying Ewe

This weekend, my wife and I had the pleasure of visiting the Flying Ewe Farm, in northeast West Virginia. Nestled in the wooded hills of the Appalachian Plateau, it is the home of Don and Susan, good friends since the late 70s, and their three pooches. A day on the farm offered a chance to catch up with each other's lives and was a welcome escape from the suburban environment of our current daily existence.

In the course of our visit, which included a dip in Big Sandy Creek, a tour of the farm and a wonderful, home-cooked meal, it became clear why our 30 year friendship has persisted. The four of us share common philosophies when it comes to politics, religion and social issues and we are especially committed to conservation and to the environmental ethics of a "low impact" lifestyle.

The older we get, the more important friends and family become. They are the fabric that reinforces our humanity and the lens through which we view our world. My thanks to Don and Susan for a relaxing, enjoyable and inspiring visit to The Flying Ewe.

Thursday, August 23, 2007

Heat, Drought and Floods

The persistent heat and drought in the Southeast and the record floods across the Upper Midwest are related to the same weather system. As mentioned in a few of my earlier blogs, a ridge of high pressure has been sitting over the lower Mississippi Valley and Southeastern States for most of the summer, deflecting Pacific and Canadian fronts to the north. Within the dome, air is sinking, heating and drying out, resulting in triple-digit temperatures and an unrelenting drought.

As excessive moisture was injected into the Southern Plains by the remnants of Tropical Storm Erin, it was swept northward along the western rim of the dome. Once in the Northern Midwest, this moisture spread out along a stationary front that was held in place by the high pressure ridge to the south. Pulses of low pressure, moving along the front, have produced recurrent, heavy rains, which move across the same swath of ground. The results: phenomenal amounts of rain and widespread flooding from Minnesota to Pennyslvania.

Wednesday, August 22, 2007

Coastal Colorado

Should you ask Americans to list wildlife species native to Colorado, most would mention bighorn sheep, elk and mountain lions. Few would include pelicans, ibis, egrets and shorebirds on their list but these birds, usually associated with southern coasts, are common summer residents and migrants on Colorado's Eastern Plains.

Late summer is the best time to observe these aquatic birds as they gather at many of the large reservoirs along the South Platte Valley. By August, large mudflats are forming along the shrinking lakes, providing ideal feeding grounds for migrant shorebirds. Large flocks of gulls also begin to congregate on and along the reservoirs; these include California, ring-billed and Franklin's gulls. American white pelicans, double-crested cormorants and western grebes gather to rest and feed on the lakes prior to migration and smaller numbers of common, Forster's and Caspian terns may also be observed. Wetlands and shallows along the margin of the lakes attract snowy and cattle egrets, long-billed curlews, marbled godwits, American avocets and white-faced ibis.

Some of the better locations to visit include Barr Lake State Park, northeast of Denver, Jackson Lake State Wildlife Area, northwest of Ft. Morgan and the Prewitt Reservoir State Wildlife Area, southwest of Sterling. My favorite spot is Latham Reservoir, southeast of Greeley; the area along County Road 48, on the south side of the Reservoir, is especially interesting.

Tuesday, August 21, 2007

The Chase

As I drove into our Colorado farm this morning, a juvenile red fox ran across the driveway. I initially assumed he had been hunting mice in our front pasture and was scared off by my truck but, within seconds, I learned that assumption was wrong. Close on his trail was a coyote and the high speed chase circled through our property. As they approached a back, enclosed corner, I figured it was all over for the fox; but, once again, I was wrong. Clearly familiar with our farm and having learned escape routes from his parents, the fox scaled a six foot fence, using a wood pile and lower tree limbs. Less agile, the coyote stared at the fence for awhile and then loped away.

Coyotes generally feed on mice, rabbits, ground squirrels, porcupine, skunk and other small mammals. They also consume birds such as grouse and wild turkey and eat a variety of berries. On occasion, especially when hunting in pairs, they may kill small deer, goats and sheep; carrion is an important food source during the winter. While this attack on a fox may have been purely opportunistic, I have found the remains of fox on the farm in the past and have no doubt that a coyote was responsible.

The fact that such an event occured on our 3-acre Littleton farm is yet another example of shrinking natural habitat. While fox and coyotes have adapted well to suburban landscapes, their usual prey is less readily available. Pet owners beware!

Monday, August 20, 2007

High Pressure Rescue

After enduring a summer of relentless rain and floods from Tropical Storm Erin, it looked as if Texas Coast residents would have to flee Hurricane Dean, a category 4 storm that was slicing its way through the eastern Caribbean. A low pressure trough in the western Gulf of Mexico was creating an irresistable target for Dean, drawing it to the northwest.

Fortunately for Texans, a high pressure ridge over the Southeastern U.S. "backed into" the Gulf, changing the wind patterns and deflecting Dean's path to the south. Assuming a more westerly track, Dean strafed the southern coast of Jamaica and is now churning its way toward the Yucatan Peninsula; it will likely end up in northern Mexico.

No doubt, many Texans feel that their prayers have been answered. The Mexican faithful, on the other hand, are left wondering.

Sunday, August 19, 2007


The Southern Rockies and Southwest Ranges have two timberlines. The lower treeline is the border below which annual precipitation is insufficient to support forest growth (20-25 inches per year). At this border, the forest gives way to shrublands, often dotted with juniper, pinon pine and other drought tolerant trees. In Colorado, this lower timberline occurs near 6500 feet; it is higher in southern Colorado and on south-facing slopes where increased temperatures and solar evaporation reduce the soil moisture content.

The alpine timberline is the high altitude border above which forests cannot develop. While low temperatures, intense solar radiation, high winds and heavy snows all play a role, the location of this border coincides most closely with the 50 degree (F) isotherm for the warmest month of the year (usually July in the Northern Hemi-sphere); in other words, along the timberline zone, the average July temperature is 50 degrees F (this average includes all day and night temperatures through the month). Above this border, which has an average elevation of 11,500 feet in Colorado, the July isotherm is below 50 degrees F and the annual growing season is generally less than 2 months. As with the lower timberline, the alpine treeline is higher in southern regions and on south-facing slopes; in this case, greater solar radiation raises the isotherm for any given elevation.

Despite harsh conditions above the alpine timberline, more than 300 plant species (grasses, sedges, low shrubs and wildflowers) colonize the tundra; almost all are perennials, capable of storing nutrients through winter for the short summer of growth and reproduction. Like desert plants, most are also equipped with succulent leaves and extensive root systems, adaptations to the dessicating effects of high wind and intense solar radiation. Readers interested in a thorough discussion of alpine timberline ecosystems are referred to the books by Zwinger, Arno and Hammerly, listed in the right column of this blog.

Saturday, August 18, 2007

Sculptors of the Land

The landscape of our Continent is a product of geology, tectonic forces and the erosive power of wind, water and ice. Though glacial topography abounds in Canada, New England, the Upper Midwest and the high western mountains, rivers and streams are the primary sculptors today. If you want to understand the topography of an area, look at a map of its streams.

Once again, our brief life span leads us to underestimate the power of flowing water. Only the occasional flash flood opens our eyes to the force that, over millions of years, molded the surface of North America. While landscapes such as the Grand Canyon and Columbia River Gorge are usually offered as examples, one might also consider the Western High Plains. Though now semiarid and home to few permanent streams, this Province is covered by a thick veneer of Rocky Mountain debris, spread across the region by large, meandering rivers over the past 65 million years.

Our efforts to harness rivers for power, flood control, irrigation and recreation, while well intentioned and beneficial, are doomed in the long run. Sediments will clog the reservoirs, the dams will eventually fail and the rivers will regain control of the land.

Thursday, August 16, 2007

Peru's Subduction Quake

Yesterday's earthquake in central Peru developed along a subduction zone. The Nazca Plate, a remnant of the Farallon Plate, is being pushed beneath the South American Plate. In such collision zones, the edge of the upper plate (in this case the South American Plate) is forced downward by friction between the plates; on occasion, this building pressure is released, the plate slips upward and an earthquake results.

Centered 90 miles SSE of Lima and 25 miles beneath the surface of the sea, the 7.9 magnitude quake lasted 2 minutes and was followed by at least 11 aftershocks; a small tsunami was also triggered by the quake. Peru officials report more than 330 dead and at least 1200 injured.

This subduction process along the west coast of South America has been going on for at least 180 million years and is responsible for the development of the Andes. As the Nazca Plate moves deeper beneath the Continental Plate of South America, it approaches the Earth's mantle and is melted, producing a chain of volcanoes at the surface. Part of the Pacific "Ring of Fire," volcanism and earthquakes will continue in this region until the entire Nazca Plate is consumed.

Wednesday, August 15, 2007

Jim, Flossie and Dean

Last week, as Hurricane Flossie churned northwestward across the Pacific, the Weather Channel advised that it would likely pass to the south of the Hawaiian Islands. Then, several days ago, the storm changed course, heading straight toward the Big Island of Hawaii. No doubt disappointed by a late start to the Atlantic hurricane season and not willing to defer coverage of Flossie to the local media, the Weather Channel dispatched their superstar, Jim Cantore, to the Islands, stationing him at ground zero to bring the full force of the storm into our living rooms.

Unfortunately, soon after Jim parked himself at the south tip of the Big Island, Flossie changed course once again, moving westward and missing Hawaii altogether. After traveling thousands of miles and adding significantly to his carbon footprint, the Storm Tracker had to be content with shots of big waves and damp pavement. Worse yet, Jim is missing out on the tropical system that is forecast for Texas and, if he doesn't get right back on a plane, might not have the opportunity to stand in the wind and rain of Hurricane Dean, now a Tropical Storm east of the Antilles.

Should all of these storms prove to be duds, Weather Channel viewers can tune into the Climate Change series by Dr. Heidi Cullen, where she will advise them how to minimize their carbon footprint.

Tuesday, August 14, 2007

Blue Whales and Krill

Blue whales, the largest animals to ever inhabit this planet, reach up to 100 feet in length and weigh up to 190 tons; females and those in the Southern Hemisphere tend to be the largest. Numbering 350,000 before the age of modern whaling ships, 99% of their population was decimated during the early-mid 1900s. Slowly recovering since the 1970s, blue whales now number somewhere in the range of 8-15,000 individuals, 2/3 of which live in the Southern Hemisphere.

Protected from human hunting, these marine giants now face a dwindling population of krill, their primary food source. Krill are small, shrimp-like crustaceans that live in the open ocean waters, feeding on phytoplankton and often massing in huge schools, containing billions of individuals. In fact, their vast numbers make krill the most abundant (by mass) animal on the planet; 85 species inhabit the Earth's oceans. Nevertheless, krill populations are diminishing, having dropped by 80% over the past 30 years in some parts of the Antarctic. The cause for their demise remains uncertain but warming sea temperatures and a reduction in sea ice are thought to play a role (krill feed on algae that accumulate on the underside of the ice shelfs). In recent decades, man has also been harvesting krill for use as aquaculture feed and for the production of krill oil, a popular health food item. Should krill populatins continue to decline, the welfare of all baleen whales and many species of penguin, seal, fish and sea birds will be threatened.

To support their massive frame, blue whales consume up to 4 tons of krill each day; much of this consumption occurs in the cold polar seas during the summer months, when the perpetual daylight fosters extensive phytoplankton blooms (and thus phenomenal runs of krill). Moving on to Temperate and Tropical seas to give birth and to breed during the winter months, blue whales feast on other krill populations along the way. Impregnated females carry their calf until the next winter and will then nurse it for another 8 months; mature females generally give birth every 2-3 years. Despite the many threats to their welfare, blue whales may live 80 years or more.

Monday, August 13, 2007

Heat Dome

A stubborn dome of high pressure has been sitting over the Southern Plains and Lower Mississippi Valley for the past two weeks and shows no sign of breaking down. Such atmospheric domes are characterized by sinking air which compresses, dries out and heats up as it drops. Hot sunny days with limited cloud cover result and the vegetation begins to dessicate. Furthermore, "pop-up" thunderstorms, which usually provide intermittent relief during summer heat waves, cannot develop under these conditions.

Since winds move clockwise around zones of high pressure, showers and thunderstorms that develop outside the dome are pushed along its rim, from New Mexico and Colorado across the Northern Plains and into the Upper Midwest and Northeast. Meanwhile, those of us within the dome have experienced a seemingly endless string of hot, sunny days, with highs in the upper 90s and low 100s; even the overnight lows remain in the 70s.

But the daylight is waning, the college kids are back in town and the glorious days of fall are within sight. Soon, this stubborn heat wave will be just another memory to embellish!

Sunday, August 12, 2007

Summer Mornings

During periods of hot, humid weather, early morning is the only comfortable time of day to be outdoors. With afternoon highs near 100, even the hours near dusk remain unpleasantly warm and it takes several hours of darkness to cool the air into the 70s.

By middle age, most of us have outgrown the late night party life and go to bed early enough to rise at dawn. This offers a clear advantage during the summer months, allowing us to enjoy the best part of the day. Wildlife, never subject to hangovers and late night social events, always take advantage of the cool morning hours and those of us who venture out in the early morning are blessed with their company. Birdsong is almost spring-like during those first hours of the day and both nocturnal and diurnal creatures are usually active.

By mid morning, the heat is building, the birdsong is fading and most wild creatures are heading for cool dens or shaded retreats. While they will venture out again in the evening, their songs will be subdued and their movements less vigorous. Only insects thrive in the heat; the rest of us tend to wilt.

Saturday, August 11, 2007

North Park

Colorado, with its alpine scenery, ski resorts, whitewater rivers and rugged canyons, attracts visitors from across the globe. But most of these tourists, and perhaps most Coloradans, are unfamiliar with North Park, my favorite part of the State. Relatively undeveloped, this scenic, intermountain "parkland" teems with a fascinating diversity of wildlife.

Bordered by the Never Summer Mountains and Medicine Bow Range to the east, the volcanic Rabbit Ears Range to the south and the Park Range to the west, this broad valley opens to the north, drained by the North Platte River and its high country tributaries. While much of the Valley is covered with sage grasslands, the upper river channels are lined by extensive willow thickets and rich, riparian woodlands. Moose were reintroduced to these mountain wetlands in 1978-79; numbering more than 600 by the mid 1990s, these large herbivores spread across the southeastern border of North Park, colonizing the Upper Colorado and Fraser River Valleys. Other stream and wetland residents include beaver, mink, muskrats, MacGillivray's warblers, willow flycatchers, Lincoln's sparrows, hermit thrushes and American dippers (not to mention trout).

The sage grasslands of the valley floor (which has an average elevation of 8300 feet) once attracted seasonal herds of bison, causing Native Americans to refer to North Park as "the Bull Pen." The Valley is now home to the Arapaho National Wildlife Refuge, the highest NWR south of Alaska. Established in 1967, this 13000 acre preserve straddles Colorado 125, between Rand and Walden. Numerous ponds dot the Refuge, attracting birds such as eared grebes, soras, American avocets, Wilson's phalaropes, common snipe and a variety of waterfowl. The grasslands of the Refuge are home to mule deer, pronghorn, sage grouse, Richardson's ground squirrels, white-tailed prairie dogs and white-tailed jackrabbits; golden eagles, prairie falcons and coyotes patrol the grasslands throughout the year and herds of elk winter in the Valley.

North Park is accessed via Colorado 14 (westward from Ft. Collins) or Colorado 125 (northward from Granby). Wyoming Route 230 crosses the northern end of the Valley, southwest of Laramie.

Thursday, August 9, 2007

Crowley's Ridge

The Mississippi Alluvial Plain covers the eastern third of Arkansas. Rising amidst this flat landscape of cropfields and wetlands is Crowley's Ridge, a 200 mile chain of forested hills, stretching from southeast Missouri to Helena, Arkansas. This ridge is an erosional remnant from the Pleistocene, a peninsula between the Mississippi River, that flowed to its west, and lower Ohio River, that flowed to its east. Late in the Pleistocene, the Mississippi eroded through its east bank near Cairo, Illinois, joining the Ohio and abandoning its original, western channel.

The bedrock of Crowley's Ridge is composed of late Paleozoic (Cretaceous) and early Tertiary sediments; during the Pleistocene, a thick layer of loess (wind blown glacial dust) was deposited atop the ridge, enriching the soil and setting the stage for its unique flora. Though close to the Ozarks of Missouri and Arkansas, the forests of Crowley's Ridge are more typical of the southern Appalachians, harboring a mix of oak, beech and yellow poplar.

Up to 15 miles wide and with an elevation ranging from 250 to 400 feet, this forested ridge was a magnet for early white settlers in the region, a welcome alternative to the flat wetlands on either side. Named for Benjamin Crowley, who established a homestead on the ridge in the early 1800s, this higher, drier strip of land is now dotted with eastern Arkansas' larger cities (Paragould, Jonesboro, Helena and others); a Scenic Parkway runs atop the ridge, connecting these cities.

Wednesday, August 8, 2007

From Flight to Flippers

Fossil evidence suggests that ancestral penguins first appeared along the coasts of Antarctica and New Zealand about 65 million years ago. It is thought that they evolved from large sea birds, similar to the modern albatross; ancestral penguins apparently found that swimming and diving for their food was more efficient than flying. Likely resembling loons and cormorants in their earliest forms, penguins gradually lost their flight muscles and their wings regressed to shorter, more functional flippers; they also developed streamlined, fat-insulated bodies, equipping them for life in the sea.

When penguins first evolved, earth's climate was much warmer than it is today and there was no Antarctic glaciation. By the mid Eocene, 25 million years later, these marine birds had diversified, spreading northward to the South American coasts, to islands of the Indian Ocean, to southern Australia and to the southern coast of Africa. In the late Eocene and early Oligocene, a dramatic cooling of our planet's climate produced ice formation on Antarctica and forced penguin populations to adapt to local climate conditions. This broader range of regional climate led to the evolution of at least 40 penguin species by the Miocene Period (20 million years ago); seventeen species remain today, living in conditions ranging from the harsh, frozen world of Antarctica to the permanent summer of the Galapagos Islands.

Tuesday, August 7, 2007

The Cascades

The Cascade Range of the Pacific Northwest began to form during the Oligocene, 36 million years ago, as the Farallon Plate subducted beneath the North American Plate. But the major Cascade volcanoes that tower above the landscape today are very young (geologically speaking), having formed within the past 2 million years.

Mt. Ranier, the largest of the Cascade volcanoes, first erupted 500,000 years ago. Much more recently, Mt. Mazama, in Oregon, erupted 6640 years ago, creating the caldera that now holds Crater Lake. The last major eruption of Mt. St. Helens (prior to the 1980 eruption) was in 1800 AD while Mt. Hood last erupted in 1805. Repeated eruptions of Lassen Peak, in northern California, occured between 1914 and 1922 and, as most of us remember, Mt. St. Helens shook our complacency in 1980.

Since the Juan de Fuca Plate, a remnant of the Farallon, continues to subduct beneath the Pacific Northwest, the Cascade volcanoes will continue to form and erupt. Our planet's natural history continues to unfold and, more than just witnesses, we are part of it.

Monday, August 6, 2007

Fear in the Heartland

The warnings began last week. Preparations were advised. Citizens were urged to use caution. Escape was suggested if possible. The news and weather channels blared the dire forecast: this would be a very hot and humid week in the Midwest! But folks, it is August.

In a country were most of us have very little to fear, the cable news channels and the Weather Channel often rely on the entertainment value of worry and fear. Watching their coverage of terrorism, illegal immigration, contaminated foods, global warming, contagious disease and the hazards of travel, it is a wonder any of us leave our homes. Attempting to fill 24 hours with weather forecasts and weather-related news, the Weather Channel has come up with fillers such as "Storm Stories" and "It Could Happen Tomorrow" to keep us tuned in. Focusing on past and future weather disasters, these shows help to ensure that we will rely on their channel to keep us out of danger.

While specific warnings about tornados, hurricanes and flash floods are invaluable in saving lives, the dramatic forecasts of other common weather phenomenon seem to induce more fear and worry than is necessary. How did we ever manage before we had this minute to minute weather coverage? Knowing these dire forecasts and having the temperature flashed at us from every building in town, we just focus more on what we can't control. Common sense is all we really need.

Sunday, August 5, 2007

Heat Shelters

One way to enjoy nature on a hot, humid day is to visit a cave. Caves form in areas with thick layers of soluble bedrock (limestones and dolomites); while these rocks were deposited in ancient seas, hundreds of millions of years ago, most of the cave erosion occured during the wet climate of the Pleistocene, which began 2 million years ago. In areas with significant annual precipitation, the erosion continues today as rainwater and snowmelt drip through the fractured ceiling, creating stalactites, stalagmites and flowstones.

In the U.S., caves are most numerous in a swath across Kentucky, Tennessee and Missouri; Mississippian limestones are the dominant cave-bearing rocks in Kentucky and Tennessee while Ordovician dolomites predominate across the Ozarks of Missouri. Mammoth Cave, thought to be the most extensive cave system on the planet, stretches along the Green River Valley, in west-central Kentucky. Other interesting destinations include Carter Caves State Resort Park, in the Tygart Creek Valley of northeastern Kentucky, and Onondaga Cave State Park, in the Meramec River Valley of southeast Missouri.

Caves are also found in relatively dry areas of the Western U.S., having formed when the regional climate was much wetter. Wind Cave and Jewel Cave, both in the Black Hills region of western South Dakota, were carved from Mississippian limestone. Carlsbad Caverns, one of the most spectacular cave systems on Earth, developed within the Permian limestone of southern New Mexico.

All subterranean caves maintain a relatively even temperature throughout the year, offering a cool retreat in summer and a warm shelter in winter. Of course, wildlife discovered this fact long before man did and a wide variety of creatures use caves on a seasonal or permanent basis. Small caves (or the entry zone of larger ones) are favored by raccoons, ringtails, bears, bobcats, mountain lions and a variety of small mammals; snakes also inhabit these areas. Various bat species are the classic cave inhabitants, using some as hibernation sites and others (especially large, southern caves) as homes for huge, permanent colonies. Deep within the caverns, blind and depigmented creatures (fish, crawfish, crickets) have adapted to the perpetual darkness of these hidden ecosystems.

Saturday, August 4, 2007


Also called barrens or xeric prairies, glades are open, grassy areas that develop on wooded hillsides. They are common throughout the southern Appalachians and Ozarks, where they typically develop on sunny, south-facing slopes.

Glades occur in areas where bedrock lies very near the surface and the soil is relatively thin. Solar evaporation, nutrient-deficient soil and steady erosion combine to keep the forest at bay and the dry, sandy conditions favor the development of prairie ecosystems. These open, rocky meadows usually harbor little bluestem, Indian grass, side-oats gramma and other grasses more typical of western prairies than eastern forest. Prairie wildflowers also adorn these clearings; Indian paintbrush, prairie dock, wild blue indigo, coneflowers, lobelia, rose-pink and prairie rose are among the more common species. Typical avian residents include indigo and painted buntings, yellow-breasted chats, rufous-sided towhees, cedar waxwings, eastern kingbirds, eastern bluebirds and wild turkeys; greater roadrunners inhabit glades of the southern Ozarks.

Over time, pioneer trees, such as cedar, juniper and redbud, begin to invade these glades. Enriching the soil with their own waste, they set the stage for various oaks, locusts and hickories to spread into these pockets of prairie; if drought and erosion do not intervene, the forest will soon cloak the hillside.

Friday, August 3, 2007

The Wild Canary

Gregarious for most of the year, American goldfinches finally pair off by mid summer, much later than most songbirds. Their late nesting behavior is timed to coincide with the lifecycle of native flora; using thistle down to construct their cup-shaped nests, these finches also wait to raise their young until weed and grass seeds are most abundant.

Due to the bright yellow summer plumage of the adult male, American goldfinches are often called "wild canaries." A favorite of naturalists and backyard birders, these small, common birds are easily attracted to Niger "thistle" feeders, where they are more than capable of feeding upside down. In late July or August, they place their nest in the fork of a sapling branch or shrub; a single clutch of 4-6 pale blue eggs is laid each year and the young are fed with softened, regurgitated seeds. By mid September, the males are molting to their dull, gray-olive plumage and the goldfinches begin to gather in large flocks once again.

Thursday, August 2, 2007

Suburban Stalker

Patient, camouflaged and efficient, a stalker haunts the landscape of suburbia. With arms folded as if in prayer, the praying mantis takes his position in the shrubbery, on decks or even on the walls of our home, calmly waiting for victims to wander by. Should another insect get too close, he snatches it with his jagged forelimbs and then patiently devours the hapless victim, one mouthful at a time.

Despite its fearsome reputation, the mantis is of no danger to humans, does not eat our plants and actually kills a large variety of harmful insects. Unfortunately, it also consumes beneficial bees and ladybugs and female mantises occasionally eat their own mates, after fertilization, of course. Eggs are laid in cocoon-like mats, usually attached to the lower branches of shrubs; those eggs not consumed by winter foragers (mice and birds) will hatch in the spring, yielding miniature mantises. Maturing to adulthood by mid-late summer, these silent predators die off with the first hard freeze.

Wednesday, August 1, 2007

Mid Day Siesta

Hot summer afternoons are the worst time of year for birdwatching and wildlife viewing. Unlike many humans, wild creatures have the common sense to escape the heat of the day; in summer, most diurnal mammals and birds tend to be active in the morning and evening hours, retreating to dens or shaded areas at mid day. Only insects and a few high-energy birds (swifts, hummingbirds and wrens) seem unaffected by the hot, humid weather of summer afternoons.

Of course, many creatures, such as raccoons, opossums, bats, armadillos, flying squirrels, fox and owls are primarily nocturnal, remaining in their dens or caves for most of the day. Cold blooded reptiles and amphibians, unable to regulate their own body temperature, are especially vulnerable to the mid day heat and must retreat to ponds, burrows or shady woodlands until the sun's rays are less direct.

Humans are likewise advised not to exercise in the mid day sun, thereby avoiding the risk of heat exhaustion or heat stroke; the latter can be fatal. And, for those of us who combine our exercise with wildlife viewing, an early morning or late day walk will be far more productive.