Ecological Features

The Birds Are Coming – Part 2

April 27, 2022 By crm

By Judy Ferris, Master Naturalist and Guest Blogger

You may not be able to tell by looking out your window, but spring songbird migration has already begun! Songbirds were slowly pushing northward into the U.S. as early as March. The tide of migratory birds will gradually increase through April, then reach a peak here in Maryland in the first two weeks of May. This phenomenon generally occurs at exactly the same time each year no matter how good or how bad our weather is.

Northern Parula – Winters in the Caribbean and Central America. Nests in eastern U. S. and Canada. Breeds and nests at ACLT. One of our first songbirds to arrive in spring. Click on the link below to listen to its song “Pa-ruuuuLA!” You will hear Parulas in the treetops of ACLT about the time the trees start to leaf out. https://www.allaboutbirds.org/guide/Northern_Parula

In light of our recent weather, you might well ask “How do birds who winter in the tropics know when to start migrating?”. They have no idea what sort of weather we are having here. Some bird species are triggered by day length. As we move from winter to spring, the days become longer. This triggers hormones in migratory birds. The most obvious effects of these hormones are 1) polyphagia – the desire to eat lots of food! Glutinous eating ensures that the birds put on plenty of fat – their primary fuel – before they head north. 2) Sexual hormones kick in. Sexual organs which shrank last fall are now reemerging. The birds begin to feel the imperative to fly north in order to be the first to claim territory and mates at their favorite nesting ground.

Scarlet Tanager – Winters in northern South America. Nests in northeastern U.S. Breeding bird at ACLT. Click below for its song which you will likely hear from the upland forests as you hike ACLT. https://www.allaboutbirds.org/guide/Scarlet_tanager

Songbirds generally fly in mixed flocks at night. Yes, these tiny birds take off at dusk, fly through the night, then settle in at a ‘rest stop’ as dawn approaches. Why fly at night? One of the primary reasons is that it is cooler. Songbirds are totally insulated with feathers and can only dump heat through their bare legs. If they flew under the hot sun, the birds would overheat and perish. In addition, winds are generally calmer at night and there is less risk of being picked off by predators.

Veery – a member of the thrush family. Winters in central South America. Breeds and nests in northernmost U. S. and southern Canada. Uses ACLT as a stopover, then continues north. Unfortunately, Veerys don’t get into the singing mood until they reach their nesting grounds. To hear their ethereal song however, click on the link.

https://www.allaboutbirds.org/guide/Veery

How do the migrating songbirds navigate in the dark? Many birds are able to navigate via the moon, the stars, and sun. New research, published in Scientific American, suggests that birds also navigate using their own personal map of the earth’s magnetic field. It takes an understanding of quantum physics to understand the details of how this works, but current thinking indicates that some migratory birds are able to ‘see’ a ‘map’ of the earth’s magnetic field with their eyes! No one knows what this map looks like to a bird, but perhaps it explains how songbirds can mysteriously navigate to exactly the same place year after year.

Most songbirds (even hummingbirds!) fly at a speed of 20-25 miles per hour during migration. They can travel 200-300 miles nightly. Like us humans, they are creatures of habit. If they find a good rest stop like ACLT, they may use that same stopover year after year as they make their way to more northerly nesting grounds. A good stopover has plenty of food for refueling, water to drink, and a nice sheltered spot to rest before departing in the evening.

Barn Swallow – Winters in Central and South America. Nests throughout much of Canada and the U. S. including Maryland. You can listen to their chatty little song by listening to link below. https://www.allaboutbirds.org/guide/Barn_Swallow/overview

Many songbirds migrate in waves. The first wave to head north are the colorful males. They are keen to be the first to return to their nesting ground to claim a good spot. They advertise their presence with their brilliant colors and plenty of singing. They spend lots of time chasing other males away. The next wave is mostly females. Females are generally duller in color than males. They are soon paired up with males and the two start work on a nest. The final wave to arrive is the immature birds. Young birds are often a bit duller in color than the adults. The dull colors help signal that they will not be involved in scrum for territory or mates, thus protecting them from hormone-crazed adults.

Common Yellowthroat – Winters in Central America and the Caribbean – Nests in most of the U.S. and a breeding bird at ACLT. You may well hear this bird sing ‘Witchity, witchity, witchity” as you walk near Parker’s Creek. Click to hear its song. https://www.allaboutbirds.org/guide/Common_Yellowthroat

White-eyed Vireo – Winters in the Yucatan and Caribbean – Breeds in eastern U.S. Breeding bird at ACLT. This bird’s herky-jerky song, sometimes emanating from shrubby areas along Parker’s Creek, is unique and one that everyone can recognize. Click to listen. https://www.allaboutbirds.org/guide/white-eyed_vireo

Whether you are a beginner or an expert, the next few weeks are the ideal time to dust off your binoculars and take to the trails in search of birds. You may see unusual birds that merely pass through the mid-Atlantic on their way north. You may also note breeding birds arriving on territory, finding mates, and nesting. Once you have surveyed every inch of a Cardinal, or better yet, a warbler with a good pair of binoculars, you will never look at them quite the same again!

How You Can Help

Migration in today’s world is a significant challenge for birds. Birds face additional challenges by simply living in the complicated world created by us humans. Since 1970, we have lost 1/3 of our birds – an astonishing 3 billion breeding birds. Each of us, however, by changing our everyday habits, can help save these feathered treasures. The bird folks at Cornell Lab of Ornithology have compiled a list of 7 Simple Actions which each of us can take to make the world a safer place for our birds. The list is summarized on the printable page below.

To learn more about 7 Simple Actions To Help Birds and how you can make a difference, click on the informative Cornell link below. https://www.birds.cornell.edu/home/seven-simple-actions-to-help-birds/

Did you miss Part 1 of this series? Click here to read it now.
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The Birds Are Coming-Part 1

April 8, 2022 By crm

Part 2 Now Available Click to Read

By Judy Ferris, Master Naturalist and Guest Blogger

Though it may be cold and windy outside as you read this, rest assured that a springtime surge of songbirds has already started moving northward. Most of our North American songbirds (warblers, sparrows, orioles, tanagers, and thrushes) head south for the winter.

Pine Warbler – This small but hardy species is one of our first songbirds to arrive in spring to breed and nest. They have already arrived this spring at their territories in southern Maryland. You may hear their warbling trills as they stake out their territories in areas of mature pines. Click on the link below to listen to the Pine Warbler’s melodic warble.

https://www.allaboutbirds.org/guide/pine_warbler

Why would tiny songbirds, most of whom weigh less than an ounce, undertake such a perilous migration each year? It’s all about insects. The timing of bird migration is tied to the springtime emergence of insect abundance which we experience here in North America.

Some species spend the winter only as far south as the southern U.S. Many species, however, are long-distance migrants; traveling to and from the Caribbean, Central America, and even South America. The average distance traveled by birds migrating from South America is about 1500 miles. Their journey may involve hop-scotching across the Caribbean to Florida or include a perilous 500-mile non-stop crossing of the Gulf of Mexico.

Hooded Warbler – Winters in the Caribbean and southern Central America. Crosses the Gulf of Mexico to reach the U. S.. Breeds in the eastern U.S. At ACLT, these warblers are often tucked out of sight in foliage. If you listen, however, you may hear their ringing song.

https://www.allaboutbirds.org/guide/Hooded_Warbler – Hooded Warbler singing. Not all Warblers warble!

Consider the following:

Pound for pound, insects contain 4 times as much protein as beef.
Insect organs are rich in fat – a far better energy source than carbohydrates.
Insects are the ideal fuel for migrating songbirds.
Insects are the baby food of choice for 96% of our songbirds.

Avian migration evolved about 15,000 years ago at the end of the last Ice Age. Many of our migratory warblers, sparrows, tanagers, and orioles evolved from tropical ancestors and have close cousins who live year round in the Caribbean, Central America, and even South America. The tropics have a high density of birds, so competition for nesting sites and food is intense. From an evolutionary standpoint, it was only a matter of time before independent-minded tropical birds broke with tradition and flew to the Florida or the Gulf Coast and beyond. What did they find? A cornucopia of insects and less competition for food and territory! While most tropical birds raise 2 or 3 chicks at a time, migratory birds who head north find enough insects to rear 5 or 6 chicks! The only drawback is that it gets cold in the north in the winter. So an autumn return trip to the tropics is a necessity. Migration is a risky undertaking and some birds are lost each year. In the end, however, both the tropical stay-at-home birds and the migratory birds successfully rear about the same number of offspring.

Our migratory songbirds evolved along with the plants, insects, and other wildlife that populated a North America unmarred by human activity. When these birds flew north from the tropics and reached our shores, they were greeted by pristine beaches and an endless green carpet of forests, grasslands, and wetlands which stretched from Florida to the boreal forests of northern Canada. For a hungry bird, this was a non-stop insect buffet. Stopovers for feeding, drinking, and resting were literally everywhere.

Yellow-billed Cuckoo. Winters in South America. Breeds throughout the eastern U.S. These birds are relatively common at ACLT, but are slow-moving and tough to spot. Your best bet is to listen for them as you walk the trails. Cuckoos make a variety of strange calls which you may have heard, but not known what it was. Click on the link to hear their variety of unusual sounds. Photo by Dominic Sherony CC 2.0.

https://www.allaboutbirds.org/guide/Yellow-billed_Cuckoo/sounds

Summer Tanager – Winters in Central and South America. Breeds in the southern U.S. As you hike in mature forests, you may hear this bird singing in the tallest treetops. Click on the link to listen.

https://www.allaboutbirds.org/guide/Summer_Tanager/overview

Birds today face a very different journey than that of their ancestors. Those previously pristine beaches are now lined with forests of tall condos. Vast tracts of woodlands have been eliminated. Replaced with shopping malls, subdivisions, and farmland. The wild places that remain are becoming so fragmented that they can no longer support wildlife – including insects.

Thus places like ACLT are increasingly precious. For birds who are just pausing in their journey, ACLT is a welcome rest stop. Like us humans, birds appreciate a good layover spot and will return year after year. Many migratory birds stay to breed and raise young at ACLT. This special place hosts a variety of breeding birds including indicator species such as Louisiana Waterthrush, Worm-eating Warbler, Scarlet Tanager, Kentucky Warbler, Wood Thrush, American Redstart, Prothonotary Warbler, and many others.

Other Resources

Calvert County is blessed with numerous areas to hike and explore. As you are out and about welcoming the arrival of spring, take time to pause, look, and listen. You may hear or see a bird that you never noticed before. If you take your binoculars with you, you may even have the privilege of observing these beautiful feathered creatures up close and personal. Be sure to check out the Calvert County Birding Trail link below to find additional areas to visit. Have fun and happy birding!

Calvert County Birding Trail – https://choosecalvert.com/birding

From ACLT's Website:

In 2006, ACLT member Leslie Starr completed ‘Summer Birds of the Parker’s Creek Watershed’, as the capstone project toward a Certificate in Environmental Studies from the Johns Hopkins University School of Business and Professional Studies. The primary goal of the project was to obtain information on the occurrence and relative abundance of bird species found during summer in the watershed. Field work was conducted in summers 1999 and 2004, with particular emphasis on the various habitats of the watershed. Further study of lists of bird species of concern as documented by various bird conservation organizations, including National Audubon, the US Fish & Wildlife Service, and the Maryland Department of Natural Resources, revealed that thirty-three such species have been present in the watershed during summer, of which twenty-nine are known to be or are possibly breeding. Read more and search ACLT’s bird database here.

Continue reading ... The Birds Are Coming Part 2

The Secret Lives of Insects #8

July 20, 2021 By crm

Dragonflies: Jewels of the Insect World

By Judy Ferris, Master Naturalist & Guest Blogger

While brightly colored insects are noticed and admired, Dragonflies are the true jewels of the insect world. Their wings shimmer in a glittering array of patterns. Their huge eyes glow like gems and their bodies are colorfully painted. Add to this their extraordinary flight capabilities and clearly, this is no ordinary creature!

To scrutinize a Dragonfly is to peer into the past. Starting with the head, we note that unlike nearly all insects today, dragonflies have minimal antennae. Their vision, however, is acute. Massive compound eyes encompass nearly their entire head. Each eye has about 30,000 facets; receptors which bring visual information to the dragonfly’s brain. (Olberg 2009) Additional adaptations ensure that their color vision is probably better than ours! (Ryo Futahashi et. al 2014) How generous of Mother Nature to endow a 320 million-year old species with vision that modern insects, and even humans, would envy. Ever had trouble sneaking up on a dragonfly? Now you know why! 60,000 eye facets are monitoring your every move!

But nature’s gifts don’t stop at the dragonfly’s head. Its legs are one of the secrets of its success. A dragonfly’s thorax is specially modified to accommodate all of its legs up front. Pushing the legs forward in this way essentially makes the dragonfly into a flying basket for scooping up food. Spiny legs ensure that no insect escapes capture. The dragonfly then, snags prey on the wing, uses its mouth to rip off the wings so that the captive can’t escape, and feasts on its victim without ever having to land. What does a dragonfly eat? Glad you asked! Dragonflies are exclusively carnivores. Mosquitoes and midges are dietary staples, but anything that can be captured in the air, including Deer Flies, Butterflies, and other dragonflies, is fair game.

Watch this 1-minute video of a dragonfly eating a mosquito. Note the positioning of the dragonfly‘s legs; basket-like and perfect for capturing prey.

Folks who study insects consider dragonflies to be ‘primitive winged’ because unlike modern insects, dragonflies are unable to fold their wings when not in use. Their wings are forever held out at a 90-degree angle to the body. Ah, but this is not just any old set of wings! The front and rear wings of a dragonfly are able to act independently from one another. This unique wing configuration is the reason that dragonflies are Masters Of The Air. They can hover like helicopters, turn on a dime, and dart swiftly from a standing start. Today’s modern insects flap their wings at a speed of about 1000 flaps per minute. Dragonflies? Hardly raise a sweat; flapping only 30 flaps per minute. These amazing flight capabilities are yet another source of envy for today’s insects! Perhaps primitive’ is not so bad after all!

Click below to watch a beautiful slow-motion video by BBC of a dragonfly in flight. 1 ½ minutes in length.

Dragonflies are superb hunters. But mighty though they may be, after hundreds of millions of years, they still remain tied to the water. Dragonfly nymphs (larvae) develop in water for months and sometimes years before becoming adults. You might expect dragonfly babies to be elegant and artistic. But NO! Dragonfly nymphs are the stuff of horror movies! Imagine a small (1/4 to 1 ½ inches long), crayfish-like creature with a large head containing a lethal lower lip (labium). The nymph’s lower lip is hinged, rather like bending your arm and tucking it in to your chest. The lip can shoot out, snag prey, and drag it back into the mouth so fast that if you blink, you’ll miss it!

To check this out for yourself, watch this excellent 3-minute video from PBS ‘Curiosity Stream’ on dragonfly adults and nymphs.

Dragonfly nymphs eat the larvae of mosquitoes and mayflies, as well as tadpoles, and even small minnows. The nymphs themselves, of course, are a favorite food of frogs, fish, and snakes. It is estimated that the mortality rate of dragonfly nymphs may be as high as 99%! (Arnett 2000). Thus, no matter how lethal your lip is, if you are a nymph, it pays to have a good escape strategy. Mother Nature had to work hard on this one but as always, came up with a novel solution.

1. A dragonfly nymph has gills in its rectum. Thus, the nymph continually takes water in and out through its anus to breathe. [No. I am not making this up!]
2. If threatened, the nymph uses the powerful muscles of its rectum to blast water out of the anus.
3. Whoosh! Powered by the blast, the nymph is jet-propelled at high speed away from danger, leaving only a camouflaging plume of disturbed debris in its wake!

Dragonflies were perfect when they were created 320 million years ago and remain so to this day. In both the larval and adult stage they are master predators; helping keep mosquitoes, flies, and other pests in check. They also serve as an important food source for other creatures. Dragonflies are good indicators of a healthy environment and clean water. How wondrous that these jewel-like super-predators, capable of astonishing aerobatic and aquatic feats, still share our world and bedazzle us today.

It ‘s easy to be smitten by these astonishing insects! If you would like to learn how to attract dragonflies to your yard, check out the link below.

Tree hugger; “How to Create a Dragonfly Garden”

https://www.treehugger.com/how-create-dragonfly-garden-4863982

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The Secret Lives of Insects #6

June 17, 2021 By crm

Ground Beetles: Midnight Marauders

By Judy Ferris, ACLT Guest Blogger

Who would imagine that a beetle with a face like this would be a gardener’s best friend? Your first instinct upon seeing this critter may be to stomp it before it hurts someone. But wait a minute!

Ladybugs, move over! It’s time we discovered the nocturnal guardians of our gardens. Night after night, unnoticed and unloved, humble Ground Beetles toil to rid our gardens of pests. They are, in fact, some of the most beneficial insects in our gardens. Since Ground Beetles are nocturnal, however, we seldom notice them. By day they hide in grasses, or beneath rocks, logs, or mulch in order to stay cool and moist. As the sun sets in the evening, however, adult and larval Ground Beetles begin to hunt. They churn below the ground, skitter atop the soil, climb plants, and even ascend trees as they forage. What’s on the menu? It’s an all-you-can-eat buffet at the Insect Smorgasbord! Ground Beetles are prodigious consumers of a wide variety of insect pests that we would happily remove from our gardens; mites, snails, slugs, caterpillars, earwigs, cutworms, vine borers, aphids, and many other insects.

Ground Beetles are members of the Carabid family. With over 2000 Carabid species in North America alone, Ground Beetles are a common insect. They range in size from 1/8 to 1 1/2 inches long. If we examine this beetle closely, we can see that it is configured to be the perfect nocturnal predator. Ground Beetles rarely fly. Instead, they use their long, agile legs to hunt and pursue prey in the darkness. Most Ground Beetles are dark and shiny. They have large eyes as befits a night hunter. Those take-no-prisoners jaws are perfect for processing all kinds of prey; from slimy slugs, to gummy-bear cutworms, to crispy-critter ants. Some Ground Beetle jaws are even designed to puncture the shells of snails.

To watch those intimidating jaws in action, check out the video below Ground Beetle vs Corn Ear Worm. Warning! The video is best not viewed immediately before or after a meal!

An adult Ground beetle can eat its own body weight in prey insects nightly. Beetle larvae are equally voracious. A single beetle larva can eat more than 50 caterpillars during the course of its development.

As a family, Ground Beetles are the master chemists of the insect world. Thanks to chemistry, many Ground Beetle species can emit a lingering noxious smell from their rear ends to discourage predators. One branch of the Carabid family, Bombardier Beetles, has elevated this talent to an art form.

Behold the Bombardier Beetle! When threatened, this elegant little beetle can aim and shoot a hot, chemical cocktail from its butt to a distance of several times its body length. The chemical blast is accompanied by smoke as well as an audible pop as the chemicals detonate. How does the beetle do this? According to researchers at Penn State University, ground beetles have a unique gland system which allows them to store toxic chemicals such as formic acid, concentrated hydrogen peroxide, and phenolics in the tip of their abdomen. When needed, the chemicals are squeezed out of the glands and moved into firing position near the anus. There, the chemicals react with special enzymes to ‘fire’ (oxidize) the chemicals; releasing heat and gaseous oxygen that shoots the boiling hot (212 degrees!) material out of the Bombardier’s butt (Marshall 2006).

For a fascinating 4-minute video from the BBC on chemical warfare in the insect world, click on the link below. You’ll see Bombardier Beetles in action at the end of the video. Impressive!

In case you are wondering… Yes, a blast from the Bombardier Beetle can burn your fingers and stain your hands. Thus, if you are lucky enough to find a Bombardier Beetle, it’s best not to handle it. Personally, however, I’m delighted to know that a squadron of Ground Beetle caretakers patrols my gardens nightly, apprehending and puncturing pests! When I do happen upon them by day, Ground Beetles are not threatening, but are instead, welcome residents. May they live long and have many babies!

To attract beneficial ground beetles to your garden, create a simple beetle refuge as described below by Landscape Designer Darcy Larum.

“Build a small raised garden bed at least 2 feet wide and 4 feet long. Plant native perennials and grasses in this bed and give it a good layer of mulch. Add some large rocks or logs for décor and ground beetle hideouts. Let debris build up enough to encourage ground beetle eggs, but not too much to snuff out plants. Do not mow, till, or spray pesticides in this area.”

Additional information on Beetle Banks: https://savvygardening.com/build-a-beetle-bank-or-bump/

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Quo Vadis, Parkers Creek Preserve

June 4, 2021 By crm

Will rapid sea level rise turn our marsh to mud flats and shallow lagoon?

By Peter Vogt, ACLT Founding Member

In the Spring 2021 Newsletter (pg.8), I speculated on the future of the ACLT as the successful land conservancy it has become. Now about the future of the Parkers Creek Preserve (PCP), its dramatic habitat diversity, an island in a vast urban-suburban sea. Our small but growing oasis is protected into the indefinite future for nature and passive human recreation. The protection is by legal, not physical fencing, and how we manage this oasis. Ecology is the response of life to physical forcing—notably climate. Absent human influences, it would be easy to predict the climate, sea level and ecology even millennia from now.

As is, what will happen especially to the salt marsh and adjoining freshwater swamps in the coming decades and centuries is awash in uncertainty. How fast will humans reduce greenhouse gas emissions? How fast and how much will climates change, and how much and how fast will sea levels rise—largely by ice loss in Greenland and Antarctica? How will tidal Parkers Creek and the PCP respond to those distant and global processes? How will PCP biota respond to warmer climates and higher CO₂? How much will the oceanic and thus the Chesapeake’s acidity increase, impairing carbonate shell growth by oysters and clams? How much will land-falling tropical cyclones intensify due to a warming Atlantic? Will land-fall frequency change? How might multidecadal variability change—confusing long term climate change predictions?

Instead of using fuzzy terms like ‘the middle of the next century’ I will hazard predictions for four “preservation milestone years.” That’s to sharpen our sense of past and future times, relating the ACLT to older Mid-Atlantic land preserves –all of which still exist today! The Boston Common (A, 1634) was the first urban park; Thomas Jefferson’s sale (B, 1815) of Virginia’s Natural Bridge as a ‘trust’; the oldest land conservancy (Trustees of Preservation, C, 1891); and the first Calvert nature preserve (Hellen Creek hemlocks, The Nature Conservancy, D, 1956). The ACLT is 35 years old this year, and will be as old as A in the year 2373, B in 2192, C in 2116, and D in 2051. While 2373 may feel unimaginably far in the future, that year is actually 35 years closer to us than 1634!

I’ll start by predicting that chemical pollution and its longer lasting effects will continue at least for some decades. Additional alien species will surely invade the PCP. These are biota not yet introduced, plus others, like fire ants, which will migrate up here, enabled by climate warming. If alligators get into Parkers Creek by 2192, would ACLT find them interesting or try to kill them off? Thousand Cankers Disease (fatal to black walnuts) is already in Cecil County, and the spotted lanternfly, chowing down on many tree species, is poised to invade from southeastern Pennsylvania. Insect populations are in decline—which would imperil bats and many of our insectivore song birds. However, future gene editing might safely deal with many pathogens, as it has with the chestnut blight. Given time, native plant species might evolve resistance while some native predators might evolve a taste for invasives.

As the Bay widens by wetland loss in Dorchester County, the increasing fetch would increase Calvert Cliff wave erosion, but warming would also decrease the effect of freeze-thaw. Mostly, climate change and sea level rise won’t have major effects on Calvert Cliffs shoreline retreat rates—see more below.

More frequent high rainfall events will increase slope erosion– but scarcely to high historical erosion rates from farmland. Increasing CO₂ will stimulate plant growth (including invasives and poison ivy) but make foliage less nutritious for insects.

Depending on future CO₂(plus other greenhouse gas) emissions, our climate by 2192 and especially 2373 would range from somewhat similar to today to tropical. After that, climates should stabilize and very slowly cool. My optimistic prediction for those distant years is a new Old-Growth forest similar but more bio-diverse than what hikers see today. Some American species will have migrated here from the coastal Carolinas or Georgia. (A pessimist might predict a species-poor environment dominated by invasives, with few trees growing large and old).

The most dramatic change in the PCP future may well be the transformation- by rapid sea level rise- of the salt marsh and adjacent freshwater swamp. They may turn into mud flats and then a shallow lagoon. A marsh doesn’t care how high sea levels will eventually get—provided the rise is not too rapid.

Sea level rise and land subsidence rates are reported in millimeters per year, where 1 mm/year= 0.39 inches/decade: RSLR means Relative Sea Level Rise, which includes any vertical movement of land, in our area subsidence. RSLR has been measured by tide gauges at some coastal sites for more than a century. Since 1993 it has also been measured by radar pulses reflected from the ocean surface by orbiting earth satellites. Land rise or fall rates are today being measured with GPS. Multi-annual fluctuations (winds, precipitation, etc.) create sea level ‘noise’ which must be smoothed out (filtered) to obtain a time series of sea level versus time. These data are then empirically fit with a simple algebraic function. This function can then be interpolated to get the relative sea level for any given time and place, and used to predict the near-term future.

Future climate change and sea level rise in Maryland have been professionally studied for decades. In 2007 the State established the MD Commission on Climate Change (MCCC), which includes a group of experts. The MCCC regularly issues reports, updating projections, and strategies for mitigation and adaptation. The most recent summary of MD sea level rise was issued in 2018. Projections have become more sophisticated, and are now couched in probability and statistics. For example, Baltimore, having Maryland’s longest tide gauge record, has a 66% probability of RSL being between 0.6 ft and 1.6 ft higher in 2050 than it was in 2000. RSLR has been accelerating at 0.084 mm/year per year—meaning +1.68 mm/year from 2000 to 2020! The prediction for Parker’s Creek would be very slightly higher.

Graphs of future sea level (and other parameters such as global temperature, CO₂, and human population) have the alarming, exponential-like shape of explosions. The curves resemble playground slides (if only 1900-2100 is shown), or hockey sticks (if the last 1,000 or 10,000 years are included). Eventually all such parameters will level off or/and decline. The question for humanity—and for the PCP– is what will happen in the interim.

Salt marshes like the one bordering tidal Parker’s Creek grow upwards via new but not decomposing organic matter from plant growth, plus any sediment washed or blown in. Marshes thrive when the RSLR is positive but slow. If RSLR increases too fast, some marshes will just migrate inland, leaving open water in their ‘wakes’. However this is possible only if the land is low and slopes are gentle. The Parker’s Creek marsh and swamp are bordered by relatively high and steep topography, thus preventing migration, i.e., a ‘wetland squeeze’. However, the hilly PCP topography also limits the amount of land flooded by future sea level rise, or land species killed by brackish water, or by shoreline erosion, were the marsh to become a lagoon.

Falling sea levels (caused mainly by ice sheets once again growing) would kill the salt marsh and turn the marsh-swamp of Parkers Creek into forest, somewhat as beaver ponds revert to forest once beavers are gone. However, sea levels won’t fall again for a very long time. Perhaps 15% of the atmospheric CO₂from fossil carbon fuels will stay in the atmosphere for millennia, enough to prevent glacial re-expansion.

What will happen in Parker’s is that the marsh may well not keep up with faster sea level rise, and would essentially drown by flooding. It’s probably not if but when! Scientists will study the process. Whether or not “we” should then artificially maintain the marsh is another matter– for ACLT land managers maybe not yet born.

Salt marshes have become more widespread globally in recent millennia, due to slowing of post-glacial sea level rise. As noted by paleoclimatologist Prof. William Ruddiman, ancient air bubbles trapped in polar ice sheets show that atmospheric methane (CH₄) and CO₂ began to increase again, respectively around 5000-6000 and 7000-8000 years ago. This did not happen during previous post-glacial times, leading Ruddiman to propose modest but significant pre-Industrial man-made greenhouse gas emission increases. The CO₂ increase corresponds to the time of rapid deforestation and farming expansion in Eurasia. The CH₄ increase corresponds to expansion of Chinese rice paddy cultivation. The global warming effects of these emissions happened to cancel out a natural 2^o C cooling and thus prevented some sea level fall. This implies that many modern salt marshes, including Parker’s, are ultimately due to mankind meddling with climate. (As it happens, Bill Ruddiman is a friend and former coworker, who in the early 70s coincidentally lived in Prince Frederick—in the Parkers Creek watershed).

US Geological Survey cores of Chesapeake Bay area salt marsh burial depths, age-dated by C14 (led by Dr. Tom Cronin of USGS), showed RSLR slowing around 6000 years ago, as the last of the Laurentide ice sheet melted away. This was more than five millennia after climate warming began. It takes time to melt a great ice sheet, and melting mostly occurs only in the warm season. There may have been further slowing to very low RSLR rates around 2000 years ago.

Sediment coring in Parkers marsh by a Johns Hopkins PhD student (Norman Froomer) in the 1970s showed the marsh layer is about 10 ft thick and 2000 years old at its base. The long-term average RSLR has thus been 1.5 mm/year, so the marsh kept up with this slow rise. (I suspect an open lagoon existed for some centuries before, but a barrier beach formed, leading to a marsh protected from Chesapeake waves).

New marsh data are being collected at present. In late 2019, the USGS (Dr. Michael Toomey) took three sediment cores in a short transect from the beach berm inland into the Parker’s marsh. This coring is part of a USGS study to see if marsh sediment piles record long-term storm surge frequency – registered by berm overwash sediment. The Covid-19 pandemic delayed analysis.

In the top 84 cm of the cores, inorganic sediment washed in from the Parker’s watershed records land clearing by early English farmers and their American descendants after the middle 17^th century. From this result, Froomer derived an average RSLR of 2.74 mm/year between 1650 and 1975. His other two study marshes, along the tidal Potomac, yielded the same result, but in Parker’s the transition from fresh tidal to brackish had migrated neither towards the Chesapeake (due to sediment input and increased runoff) nor inland (due to sea level rise and westward migration, by shoreline retreat, of the barrier beach). Those 10 ft thick marsh deposits are a priceless archive of past PCP watershed and marsh vegetation, historical land use, and sea level rise. Science has so far barely skimmed this archive.

Meanwhile CBL scientist Dr. Lora Harris and her Lab Assistant Jessica Flester have deployed (2012) four rSETs (rod-surface-elevation tables) in the marsh. The repeated measurements will determine how well the Parker’s salt marsh keeps up with RSLR. The data since 2013-14 offer good news. There is no tide gauge in Parker’s Creek, but Maryland tide gauge data reported in 2018 show RLSR rates since 2000 ranging from 4.2 to 7.3 mm/year. However, Parker’s Creek marsh elevations at the four rSET sites increased even more rapidly (+5.9-+13.9 mm/year), showing the Parker’s marsh (and others in our region) are so far doing well in keeping ahead of the sea level rise. Ironically, the main gas (CO₂) that is increasing global sea levels is also encouraging marsh plant growth.

Any change in living marsh vegetation over time and space can record the response to RSLR acceleration, which would increase both salinities and flooding frequency. For example, we predict the Parker’s salt marsh species like Spartina patens (salt hay) will be gradually displaced by the more salt tolerant S. alterniflora (smooth cordgrass). Upstream in the freshwater swamp, narrow-leaf cattail tolerates a bit more brackishness than the common broadleaf cattail. The May 16, 2020 drone image shows some dying trees in the small swamp forests—is this evidence for accelerated sea level rise and increased flooding, or/and increased brackishness? Or was this forest an ‘unnatural’ consequence of greatly increased sediment input from eroding farmland?

According to Dr. Patrick Megonigal of SERC (Smithsonian Environmental Research Center), recent research in the Kirkpatrick salt marsh shows that sedges tolerate more flooding and thrive more under higher CO₂ concentrations than do grasses like S. patens. Sedges use a different type of photosynthesis than grasses. Being familiar with the Parker’s marsh, Dr. Megonigal pointed out that our marsh vegetation is already dominated by types of plants like sedge, which should help stabilize our marsh against faster RSLR and extend marsh life by several decades.

How fast is sea level rising today? In recent decades relative sea levels have been rising around 3.5 mm/year in our part of the Chesapeake region, including the PCP. Of that, about 1 mm/year is due to land sinking, the remaining Earth response to the giant Laurentide ice sheet once north of here. Humans can’t change that. Of the remaining 2.5 mm/year, about half has been due to ocean warming and expansion, and the other half to glacier/ice sheet melting adding water to the ocean. Satellite sea level measurements beginning in 1993 plus data from ice sheets suggest that the effect of melting now dominates and has accelerated, with present RSLR likely more like 4.5 mm/year. Limited data from other marshes suggest that the Parker’s salt marsh may not keep up if this rate doubles.

An additional effect is possible Gulf Stream weakening, an additional RSLR effect in the Mid-Atlantic. The Gulf Stream circulation ‘holds’ a broad 3 ft high dome of water centered over the Bermuda region. This is the same Coriolis ‘force’ which also causes the counterclockwise circulation of surface Chesapeake Bay waters and thus keeps Parkers Creek tidewater less salty than across the Bay. If the Gulf Stream weakens, the dome height decreases, and water levels rise here, west of the Gulf Stream. For a salt marsh, even a few inches rapid sea level rise matters. Increasingly frequent ‘nuisance flooding’ (during normal high tides) in the Mid-Atlantic may in part reflect Gulf Stream weakening but is scarcely an issue for a nature preserve.

Long-term (multi-year) natural atmospheric fluctuations—reflected in temperature, winds, or precipitation, and unrelated to climate change—complicate identification of true climate change. One such natural multi-decadal oscillation has a quasi-period of 70-90 years and is generated within overturning of the Atlantic Ocean. This oscillation influences the atmosphere and is recorded as precipitation ‘cycles’ in bald cypress tree rings in the coastal Carolinas and by salinity-sensitive Chesapeake plankton sampled in sediment cores east of Parkers Creek (More watershed precipitation in the Bay watershed means lower Bay salinities). Whether climate change will affect this oscillation—which has been happening for millennia—remains unknown, but both the public and politicians may confuse such long term oscillations with climate change. As two possible local examples, the extreme 2002 drought might easily be blamed on climate change, but occurred 71-73 years after a worse drought (1929-31). In 2002 the freshwater tidal part of Parker’s Creek was brackish for weeks, and upstream of that, the creek turned to isolated mud puddles. How freshwater fish species survived or returned to Parker’s Creek remains a mystery. Some very cold Calvert winters during 1893-1905 were followed more than 80 years later by similar exceptional cold in the late 1970s-early 80s. Yes, I even ice skated on the Chesapeake Bay, Patuxent River, and Parkers Creek! Should we experience unusual cold winters in 2050-60, some might argue that climate warming has ended!

By far the most dramatic water level changes are short term storm surges caused by tropical cyclones-especially for storms tracking northeast with centers west of Parker’s Creek. The amplitude of such surges (roughly + 6 ft during Isabel in 2003) dwarfs the normal tidal range (about 1.46 ft at Parker’s Creek). Surge heights will be greater if Chesapeake shorelines become extensively armored. Future surges will at least add to the expected RSLR, and at worst be more severe if tropical cyclones are strengthened by the warming Atlantic. Future surges will carry brackish water up into parts of Parkers Creek presently upstream of the tides. Whether the PCP fully recovers from future extreme droughts, storm surges and widespread tree blowdowns will test its ecological resiliency.

Different future greenhouse gas emission scenarios give widely different model predictions (2017) of the 2100 increase over 2000 sea levels, from the most optimistic (+ 1 ft) to the most pessimistic (+8.2 ft). The +1 ft prediction is scarcely realizable because it assumed anthropogenic emissions would peak by 2020, which they have not, and that they will decline to zero by 2100. These are the mean global values, and sea level will likely be somewhat higher here. Our 1 mm/year land subsidence adds 4” per century, and any Gulf Stream weakening would add more inches. I will guesstimate +3 ft for the Parker’s Creek area between now and 2116. By 2373 a worst case might be up to +15 ft.

If RSL rises more than ca. ca 6-8 ft in the PCP area, the preserved PCP cliffs south of the Parker’s beach will slow their erosion and shoreline retreat rate (presently around 4”-8”/year) by Chesapeake’s waves, while the PCP cliffs north of the beach will start eroding faster. This gradual switch reflects 1) the tilt (dip) of the Miocene layers (strata) downwards to the southeast and 2) a more erodible layer, the Parkers Creek Bone Bed, currently exposed to wave action south of the beach, will disappear below the waves due to rising RSL. Meanwhile the same layer, currently above the reach of waves further north, will become accessible to wave erosion. Because the barrier beach protecting the salt marsh appears ‘pinned’ to -and thus aligned with- the cliffs, the slow clockwise rotation of the beach and cliffs will change to counterclockwise, and loss of salt marsh behind the beach will switch from greater in the south to greater in the north. These gradual changes are driven by the geology exposed in the cliffs but are speeded up by faster SLR.

Shoreline retreat along the PCP cliffs and the 1300 ft long barrier beach have not been specifically studied. The process can be envisioned as giant horizontal band saw cutting into the shore while gradually being raised. The beach and offshore sand bars migrate inland as they follow the saw. For an assumed ball-park average retreat of 3” per year, the PCP 7700 ft long shoreline will have migrated respectively 2.5’, 24’, 43’ and 88’ inland by the milestone years 1951, 2116, 2192, and 2373. By 2116 the Bay will therefore have taken about 4 acres of present PCP (including 0.7 acres salt marsh). By the year 2373 the corresponding land loss would be 16 acres total and 2.6 acres marsh. While sea level rise likely won’t much affect retreat rates, there might be little no shoreline retreat at all had it not been for increased anthropogenic greenhouse gas—but also, as suggested above, no Parker’s Creek marsh.

The sand budget of the Parker’s Creek barrier beach has not been studied. Because long-shore drift causes the beach to gain sand in the north and lose sand at the south, well-intentioned efforts to armor the cliffs and also reduce inland erosion north of the barrier beach may starve the beach. Storm waves would rapidly erode the salt marsh in the absence of the barrier beach. It is unknown whether high rainfall events allow Parker’s Creek to carry sand to the beach from tidewater limits, where the stream flows fast enough to have a sandy bottom. If it does, climate change, causing more frequent high-rainfall events, might help sustain the barrier beach.

RSLR predictions are closely related to greenhouse gas and therefrom temperature rise predictions. If mankind holds the rise to +2^oC, the 2116 RSL global mean may be only +1.5 ft, and the Parker’s marsh (+2 ft) may well survive. My +3 ft guesstimate for 2116 implies an average RSLR of around 9 mm/a, roughly twice the present rate. Will the Parkers marsh keep up? Maybe not—rates later during this century have to rise above 9 mm/year for that to be the average.

The spread of predictions reflects not only the largely geopolitical uncertainties of future greenhouse emissions, but also the response of two of the three major ice sheets—Greenland and West Antarctica. Each of these hides a ‘wild card.’ The current global CO₂ is around 415 parts per million, already the highest in at least the last 3 million years. If the average rate from now to 2100 is held near the present one (2.5 parts per million per year), the concentration would be around 600 ppm then. (900 ppm is a very pessimistic prediction which I think won’t happen: at least in the US, per capita greenhouse gas emissions have begun to fall).

USGS has sampled sediments from 3 million years ago and from 15 million year old Calvert Cliffs sediment—including from the PCP– to understand earlier warmer climates with higher greenhouse gas concentrations. However, there was much less ice on the planet during those warm times. Sea levels were much higher. There were no extinctions. However, we are now in uncharted climate territory—there is no known precedent for this much greenhouse gas and this much land ice at the same time.

Mass loss of the Greenland ice sheet has greatly accelerated in recent years, but this ice sheet is contained in a depression bordered by mountains. However even the mass loss so far has created a large pool of colder, fresher water (from admixed meltwater) south of Greenland. The climate cooling there is not good news, because the Gulf Stream system has a deep return flow. Turn off your water main and no water flows out of any faucet! If the cold ocean water is too fresh, it won’t sink, thus slowing or even stopping the return flow. A return flow shutdown apparently happened by rapid draining of a giant glacial meltwater lake from the Laurentide ice sheet 13,000 years ago, causing a 1200 year return to glacial climates in Europe and here. The climate here turned glacial in less than a century! Is the cold-water pool related to Gulf Stream weakening? A return to cold climates is unlikely because there is no large meltwater lake today, and because ice sheets can’t melt fast enough.Mass loss of the Greenland ice sheet has greatly accelerated in recent years, but this ice sheet is contained in a depression bordered by mountains. However even the mass loss so far has created a large pool of colder, fresher water (from admixed meltwater) south of Greenland. The climate cooling there is not good news, because the Gulf Stream system has a deep return flow. Turn off your water main and no water flows out of any faucet! If the cold ocean water is too fresh, it won’t sink, thus slowing or even stopping the return flow. A return flow shutdown apparently happened by rapid draining of a giant glacial meltwater lake from the Laurentide ice sheet 13,000 years ago, causing a 1200 year return to glacial climates in Europe and here. The climate here turned glacial in less than a century! Is the cold-water pool related to Gulf Stream weakening? A return to cold climates is unlikely because there is no large meltwater lake today, and because ice sheets can’t melt fast enough.

The West Antarctic ice sheet may have tipping points. Major ice streams like Thwaites Glacier that drain it are presently ‘pinned’ by grounding out on the continental shelf. Recently measured melting of ice sheet underbellies by warming sea water, coupled with faster surface melting, may cause this thick tongue of ice to lift from the sea bed. This might trigger rapid retreat by iceberg calving. Rapid collapse of the entire ice sheet may then be irreversible, something not yet captured in computer models. Some glaciologists studying the Thwaites suggest this tipping point may arrive as soon as 2060. By 2051 we will know much more.

The loss of polar ice sheet mass also slightly changes the Earth’s gravity field and thus the shape of the global ocean surface, i.e., sea level. Counterintuitively, the loss of Antarctic ice has more than twice the effect– increasing Maryland sea levels– compared to loss of Greenland ice.

We might take comfort in the resilience of the biosphere to dramatic climate- including sea level- oscillations especially in the last half million years. There have been few if any extinctions due to these changes. The megafauna (e.g., mammoths and sabre tooth cats) extinctions may be the only exception if rapid cooling 13,000 years ago was a cause, but other studies indicate the extinctions and climate change had the same cause).

As recently as 12,000 years ago, when people were already regionally present, the present PCP was forested with taiga conifers, and there was no Chesapeake Bay. Pollen studies suggest that it took only about a century for our present warm temperate hardwood forest ecosystem to migrate up here from the Gulf Coast once climates warmed around 11,300 years ago. Annual layers in Greenland ice cores tell us that this warming came with shocking speed but did not increase extinctions above background levels. The global warming only took about 40 years, in three different 5 -year spurts, probably driven by instabilities in ice sheets no longer present today. A five-year temperature anomaly today would not be recognized as climate change! The subsequent climate stabilization—until now– enabled the spread of agriculture and growth of civilizations.

The species responsible for our climate change and imminent coastal inundations may seem to be the biggest loser, but it’s also about many other biota that may now become extinct or further decline in population and range. Much of this is due to habitat loss-like deforestation and fragmentation- not caused by climate change. Rising temperatures, sea levels and CO₂ concentrations are only a part of how humans have stressed the biosphere. The future of ‘nature’ in the Parker’s Creek Preserve depends very much on what happens beyond the preserve—not only future climate change as discussed above, but also– to name just two examples– habitat destruction in the Latin American wintering grounds of migrant birds which nest in the PCP during summer, and the herbiciding of distant milkweed needed by migrating Monarch butterflies.

The ACLT-managed Parkers Creek Preserve can’t have any significant global impacts (except perhaps by land preservation and management examples). However, the PCP and especially the marsh is a priceless natural laboratory for studying how a relatively pristine Mid-Atlantic ecosystem naturally responds to climate change. This was a major reason for Maryland DNR support for PCP land preservation. The ACLT Science Committee and others have already made a great start in studying diverse components of this natural laboratory.

For helpful corrections and comments, I thank (in alphabetical order): Greg Bowen (Executive Director, ACLT), Denise Breitburg (SERC, ret.; now chair of ACLT science committee), Lora Harris (Chesapeake Biological Laboratory, CBL), Pat Megonigal (Smithsonian Environmental Research Laboratory, SERC), Bill Ruddiman (Univ. of Virginia, ret.), and Deb Willard (US Geological Survey)