Forest Restoration #187, treatment January 2012
I made a rather poor choice for January’s Restoration, stuff although it seemed a good idea at the time. Seeing that the summer storms had deposited numerous plastic bottles and other trash in the vicinity of the Bluebelt Pond at Meisner and Rockland, I thought that it would be both a good idea and a change of pace for us to do a clean-up in that area instead of our usual vine cutting and invasive removal. Just after our calendar deadline had passed and there was no turning back, I took part in a night hike in the Greenbelt. Fall had been underway for some time, and as we crunched past the pond I suddenly thought “leaves!” What if all the trash is covered? A few steps further and I thought “SNOW!” Well, I rationalized, purely by chance we usually have good weather on Restoration days, so it will probably be OK, and in preparation I purchased another box of sturdy trash bags and a package of latex gloves to supplement the leather and cotton gloves we already have. In any case, I thought, if necessary we can always change the plan on the fly and cut vines instead.
Of course Saturday morning saw the first significant snow of the season, an inch on the ground by 10:00 and the roads starting to sleet up. When Judy deposited me at our meeting place, only Chuck and Elaine had chosen to brave the weather. Since the day seemed so unfriendly, we really didn’t expect anyone else to appear. We waited for about 10 minutes after the meeting time to see if anyone else would show up, and then walked over toward the pond to see if there was any likelihood that we could collect trash. It was obvious that trash collection would be at best difficult, and not very effective as well, so we decided to make a loop around the adjacent trails and cut vines instead. When I came home that afternoon my wife, Adele, told me that there had been 4 phone calls that morning asking whether the Restoration would take place. I’m sure that some other volunteers had come out but were delayed by the condition of the streets and had been unable to find us.
Our work was very easy although somewhat cold. We had done much invasive removal in that area in the past, so there were few major vines to cut away. We just strolled along, making a loop over the co-aligned Red and Yellow trails to the cross-over to the White trail, and then returned to the pond, pausing whenever we saw saplings entwined with Japanese Honeysuckle. On a few saplings the Honeysuckle had grown woody and thick enough to begin to cut into the bark, but on most the vines were still young, soft and loose. We chatted, cut vines away, and rather enjoyed the morning. Although colder than forecast – the temperature was supposed to rise above freezing by noon, which didn’t happen – the snow tapered off, hardly falling at all while we worked. It was encouraging to see how few heavy vines were there, although we did note that small clumps of Japanese Barberry were again coming up close to the Buttonbush swamp where they had been almost eradicated. Those would have to be tended to in summer when the ground is softer. While uprooting some of the Honeysuckle I noticed small insects bouncing into the shelter of a fallen branch. “It must be 28 degrees,” I said to myself, “how can these cold-blooded bugs be so active?” Then I realized that beneath the snow it would be considerably warmer, and that these creatures had come up with the leaf litter I exposed.
These little bugs were springtails, sometimes called snow-fleas, six-legged creatures that are often seen on winter snow even when air temperatures are below freezing. They are suited to winter because their body fluids have anti-freeze properties which prevent ice crystals from forming and piercing their cell membranes. Destruction of cell membranes by ice crystals cause leakage of vital fluids and death when a cold-blooded animal freezes. Springtails are active and very tiny, appearing like little dark flecks of pepper that jump about. When I was a youngster, these creatures were considered to be a group of primitive insects, called Collembola, but now they seem to have been spun off and are in a group of their own called the Hexapoda (having six legs, just like the Insecta). All insects have external mouthparts (this is one of the things that make them seem so alien to us; take a look at the feeding end of a grasshopper or beetle and see if that doesn’t give you a chill), whereas the mouthparts of springtails are concealed in an oral cavity. In that way they are a little like us; our jaws, teeth and tongue are concealed in the cavity of the mouth, whereas an insect’s feeding equipment is all displayed outside. It was this difference, and a few others, that led entomologists to oust the Collembola from the Insecta and put them in a separate place in the family tree.
Springtails are mostly seen out on the snow, but that’s just because they are most visible that way. It’s easier to see these small black flecks against white snow than it is to see them against dark leaf litter where they live and feed on other, more tiny organisms and decaying organic material. What is surprising is that we don’t see them more often, because they certainly are plentiful; one European study estimates their numbers at over 16 million in each acre of forest. Why they come out on the snow is another question. Entomologists – they’re still interested in springtails even though they kicked them out of the Insecta – have suggested that perhaps this is an easy time to find each other and mate while other aggressive insects that might be predators are not present. This mating business, however, is not necessarily very personal. Springtails don’t have external sex organs. The males of most species produce small packets of sperm called spermatophores that they perch on small columns they excrete and leave about in hopes that a female will wander by and pick them up. No doubt pheromones or some other attractants are involved to entice the female to do so. Other springtail species are more direct, and the males deliver the packets to the females. If springtails come out on the snow to find mates, it must be those that employ the latter personal delivery service. The springtails get their common name because most of them really do have spring tails. Folded up at the rear of their body is a tiny forked appendage called a furcula that is cocked against their abdomen and held under
tension. When the springtail is alarmed, it triggers this fork loose which flips against the ground and flings the springtail away from danger. You could view this organ with a hand lens if you were able to capture and immobilize one of these jumping specks of “snow pepper.”
Given the lack of volunteers, not forgetting my very cold thumbs, we decided to forgo our usual post-restoration walk. This, however, gave me an opportunity to think about some of the factors that may operate to change the composition of our natural environment, some subtlety and some drastically. I mentioned having recently taken part in a night hike of the Greenbelt. That hike made me aware of a disturbance that otherwise would have escaped my notice: light pollution. If you are a birder or have an astronomical bent you are no doubt very aware of light pollution. The brightness of stars is ranked by magnitude: a first magnitude star is a star that appears bright in the sky, while stars of the 2nd magnitude are less bright, 3rd magnitude stars less so and so on. As you might have expected, there are few stars of bright magnitudes and many more less bright stars. In our latitudes, there are only about 20 stars of 1st magnitude or brighter to be seen in the entire sky, and since we only see the stars in that part of the sky visible during nighttime, we see far fewer than that. On the ocean far from land the sky seems painted with thousands of stars, which are visible down to the 4th and 5th magnitudes. On land, however, close to cities with well lighted buildings and roadways it is difficult to see stars even of the 2nd magnitude, and the sky appears impoverished. On a clear night in New York City we can at best see 15 stars at any one time! To see more we have to go to the interiors of large parks or to the waterfront far from roadways and large buildings. City light is reflected from dust and water vapor in the sky, and the bounce-back lightens the sky and obscures the stars. This is one reason that earth-based observatories are built on mountaintops far from city lights. In the past few decades birders have become aware of how light pollution, especially light from tall structures, can affect migrating birds, trapping some of them like moths around a flame so that they circle the lights for hours burning up precious body weight in useless flight, weight that should have been a reserve to help them court and nest when they reached their destination. Locally the concern of birding organizations has persuaded some managers of tall building to darken their upper floors during periods of bird migration, and the operators of the 9-11 tribute to periodically extinguish the powerful spotlights to allow birds to escape the beams.
The concern about birds and light pollution surfaces especially during migration time, and gets a lot of press, but are other effects we know little about. The problem is that in general we just don’t know very much about the different ways light pollution effects our environment. In the long history of the world, apart from lightning during storms, bright nocturnal light has been around for only a brief period. Although in major cities gas light began to be used for street lighting in the early 1800s, it was really only after the introduction of Edison’s electric lamp that the employment of outdoor artificial light began to explode in the late 1880s. Some English birders, observing even then how vast numbers of flying insects were attracted to and killed by outdoor lights at night, began to worry that nesting songbirds, all of whom depend on capturing insects to provide protein for their nestlings, would begin to suffer a lack of food, and that artificial light would have an impact on songbird survival. To my knowledge, no-one has yet thoroughly studied this aspect of light pollution.
There are similar concerns about bats and artificial light, and recent studies suggest that these effects can be very complex indeed. A European researcher examined the activities of one species of bat whose habit was to live in and around human structures and to hunt for flying insects along hedgerows when darkness fell. In this case the researcher was less interested in the effect of light on the insects as she was on the effect of light on the bats. She found that installing a few streetlights drove the bats away from the hedgerows where they hunted and caused them to leave their daytime refuges later than usual. The result was a diminution of the area available for the bats to hunt, and less time spent feeding there. This produced a change in nutrition causing the bats to have less body weight and more feeble offspring. The researcher hypothesized that without interference the bats would have chosen the most optimal routes – routes shortest and safest – to reach their feeding areas, and that when streetlights were introduced they would be more exposed to predation by owls. They would have to fly further afield and spend more time hunting in sub-optimal areas, and that in some case they would be forced to abandon some preferred feeding areas completely.
Light pollution affects other vertebrates as well, some of them very endangered creatures. Sea turtles are for the most part declining in numbers. Much of the decline is due to human intervention, especially to loss of beaches on which they have nested for millennia. Marinas, breakwaters, pilings and seawalls have replaced many of the beaches, and humans swimming, jogging, and driving ATVs on the beach disturb existing successful nests. Dogs, racoons and other nest predators that have been introduced from other areas put paid to many more. However, light pollution plays perhaps the greatest part in the turtles’ decline. Should a nest be successful and young turtles hatch, they must quickly make their way to the sea, running a gauntlet of predators that would snatch them off the beach if they could. Evolution has programmed the young turtles to find the ocean by going toward the brightest part of the horizon, and in an undisturbed environment shrubs, grasses and high dunes will make the horizon on the shore side darker than the horizon on the sea side. With the lighted horizon as their guide the young turtles have a fighting chance to reach the sea before predators find them at first light – or at least have a fighting chance if roadway lights, billboards and the bright windows of beach-front condos don’t lead them astray. As with the birds, turtle rescuers have persuaded some owners of beach-front properties to extinguish their lights during the season of turtle hatching.
But… light pollution in the Greenbelt?? What’s that all about? I mentioned having recently been on a night hike that started at St. George and eventually wound through parts of the Greenbelt. The city part of the hike was uninteresting to me, so I elected to meet the hikers where they entered John Deere Park. They were running a bit behind, so as dusk fell I elected to proceed alone slowly with the plan of meeting the hikers at High Rock Park. The night was overcast with a waning moon, and soon I had to resort to use of a headlamp. When I approached the Overlook at Richmond Golf Course I saw a Greenbelt very different from what I was accustomed: the woods there are but a narrow band, and from one side to the other were brightly lighted by the security lights of a nearby home. By that time my vision had adapted to the night, and unless I completely averted my eyes the light was painful. As far as I could see, trees cast sharp shadows across the winter ground. A poor deer mouse, I thought, would certainly feel exposed and vulnerable to owls or other predators, assuming that the light wouldn’t make those hunters shy as well. No doubt in warm weather it would be a barrier for many other creatures as well. I wondered how many night-flying insects it would pull out of the dark woods and whether it would have an effect on the few remaining large, beautiful silk moths that one might encounter in summer. Wouldn’t it have been better if these security lights had been hooded and directed so as to not waste energy lighting up the woods? And wouldn’t it have been even better if they had been controlled by motion detectors so that they would light only when necessary? That would seem to benefit both the home owner and the environment.
Life has evolved from the ancient past under a set rhythm of light and dark, and we must expect some kind of disruption of ecological relationships when this rhythm is disturbed. Many small mammals beside bats forage under the cover of darkness, and it’s pretty obvious that they do this to avoid predators, not because of fear of sunburn! If the addition of light changes their feeding habits, it must also affect what they feed upon. Night-flying insects are especially susceptible; although parasitic wasps are probably a more significant cause, UV light from mercury-vapor lamps, commonly used to light parking lots and roadways, have been implicated in the decline of Luna Moth populations, (The Luna Moth is the beautiful lime-green moth we see in Lunestra commercials. Low-pressure Sodium Vapor streetlights emit less UV light and are less disruptive to insects, but the well-being of insects is rarely a concern, and many people object to the color of these lights.) Artificial light may interfere with more than feeding. Exposure to light at the wrong time may interfere with finding a mate and successful reproduction. In tropical regions many night-blooming flowers depend upon bats and night-flying insects for pollination, and the intrusion of artificial light is increasingly suspected to be a reason for the failure of some of these plants to reproduce. Luckily, few of the native wildflowers of our locality require nocturnal pollination! One has to wonder how far-reaching and subtle photo-effects are in the natural environment, but little research exists. We all know the light is vital to the growth of green plants, the maturation of seed and the timing of decay and preparation for the winter, but little study has been done on other than upon agricultural plants. We know that small organisms in ponds move up and down the water column depending on the temperature and the amount of light, and that one study has suggested that artificial light aids the growth of algae on the water’s surface by forcing zooplankton that would normally graze the surface algae at night to greater depths. We also know that artificial light can inhibit nocturnal feeding and mating of some frogs and other amphibians, but we have that knowledge for only a very few studied species, not enough to estimate the effect of an additional streetlight on nearby Spring Peepers. There’s very little knowledge of the different ways that artificial light might alter the ecology of a pond. There’s real truth in saying that there is more we don’t know than we do know, especially about ecological relationships. As far as artificial light is concerned and its disruption of the activity of small nocturnal animals, we might as well be “completely in the dark.”