Lost Woods (15 page)

The dune land is a place of overwhelming silence, or so it seems at first. But soon you realize that what you take for silence is an absence of human created sound. For the dunes have a voice of their own, which you may hear if you will but sit down and listen to it. It is compounded of many natural sounds which are never heard in the roar of a city or even in the stir of a small town. A soft, confused, hollow rustling fills the air. In part it is the sound of surf on the beach half a mile away – a wide sand valley and another ridge of sand hills between us – the deep thunder of the surf reduced to a sigh by the intervening distance. In part it is the confused whisperings of the wind, which seems to be never wholly still there, but always to be exploring the contours of the land it made, roaming down into the valleys and leaping in little, unexpected gusts over the crests of the sand hills. And there are the smaller voices, the voices of the sand and the dune grass. The soft swish of the grass as it dips and bends in the wind to trace its idle arcs and circles in the sand at its feet. Arcs, especially on the southeast side of the grass, mean unsettled weather, so they say; whole circles foretell fair weather because they show the wind to be blowing alternately from different quarters. I cannot say as to that; but the scribblings of the dune grass always enchant me, though I cannot read their meaning.

I knew the history of that land, and there, under the wind and beside the surf that had carved it, I recalled the story –

I stood where a new land was being built out of the sea, and I came away deeply moved. Although our intelligence forbids the idea, I believe our deeply rooted attitude toward the creation of the earth and the evolution of living things is a feeling that it all took place in a time infinitely remote. Now I understood. Here, as if for the benefit of my puny human understanding, the processes of creation – of earth building – had been speeded up so that I could trace the change within the life of my own contemporaries. The changes that were going on before my eyes were part and parcel of the same processes that brought the first dry land emerging out of the ancient and primitive ocean; or that led the first living creatures step by step out of the sea into the perilous new world of earth.

Water and wind and sand were the builders, and only the gulls and I were there to witness this act of creation.

Strange thoughts come to a man or woman who stands alone in that bleak and barren world. It is a world stripped of the gracious softness of the trees, the concealing mercies of abundant vegetation, the refreshment of a quiet lake, the beguilement of shade. It is a world stripped to the naked elements of life. And it is, after all, so newly born of the sea that it could hardly be otherwise. And then there is the voice of the sand itself – the quick sharp sibilance of a gust of sand blown over a dune crest by a sudden shift of the breeze, the all but silent sound of the never ending, restless shifting of the individual grains, one over another.

I am not sure that I can recommend the dunes as a tonic for all souls, nor for all moods. But I can say that anyone who will go alone into the dune lands for a day, or even for an hour, will never forget what he has seen and felt there.

18

[1953]

The Edge of the Sea

THIS PAPER,
given the same title as her forthcoming book, was presented at the American Association for the Advancement of Science Symposium, “The Sea Frontier,” and was the only purely scientific paper Carson ever gave to a professional academic organization. In it she pursues such broad ecological questions as “Why does an animal live where it does?” and “What is the nature of the ties that bind it to its world?” The paper reflects Carson’s meticulous field research and the imagination with which she could apply the latest theoretical research on climate and temperature change to her general investigation of the evolution of life along the shoreline.

Although she defined herself as a scientist who wrote for the public, Carson could hold her own with the most advanced research biologists and earn their respect. In a letter to a friend, however, she admitted she was uncharacteristically nervous about her presentation at this symposium because her mentor, Henry Bryant Bigelow, Harvard scientist and former director of the Woods Hole Oceanographic Laboratory, was in the audience. Carson later dedicated the 1961 edition of
The Sea Around Us
to Bigelow.

IN RECENT YEARS
I have been dealing with the ecology of the seashore: with the animal and plant communities of the rocky coasts, the beach sands, the marshes and mud flats, the coral reefs and mangrove swamps. I have been thinking about the relations of one animal to other animals, of animals to plants, and of the animal or plant to the physical world about it. Always in such reflections one is made aware of the complex pattern of life. No thread is found to be complete in itself, nor does it have meaning alone. Each is but a small part of the intricately woven design of the whole, for the living organism is bound to its world by many ties, some of them relating to biology, others to chemistry, geology, or physics.

For example: perhaps we discover that an animal we have found year after year in the same place suddenly is found there no more, and eventually it appears that the whole population of this creature has shifted its range; that it has done this, moreover, in response to a change in a single factor of its physical environment – the temperature of the water.

Or we may find that a certain marine worm is so specialized in its living requirements that it can live in one kind of sand and one only; and moreover, that its very young stages – the larvae whose age is measured in hours or days – are able to find and to recognize sand of these particular qualities with a precision that few human students of geology could match.

Or again perhaps we discover a sudden and quite mysterious change in the ability of a marine animal to grow or to reproduce, or in the ability of its larvae to exist in the accustomed places, and perhaps we are led to suspect a subtle change in the biochemical nature of the seawater.

All or any of these things are enough to convince us that we, as biologists, cannot exist in a comfortable ivory tower of our own; that it is quite necessary that we concern ourselves with the related sciences if we are to understand the creatures of the marine world.

The edge of the sea is a laboratory in which Nature itself is conducting experiments in the evolution of life and in the delicate balancing of the living creature within a complex system of forces, living and non-living. We have come a long way from the early days of the biology of the shore, when it was enough to find, to describe, and to name the plants and animals found there. We have progressed, also, beyond the next period, the dawn age of the science of ecology, when it was realized that certain kinds of animals are typical of certain kinds of habitats. Now our minds are occupied with tantalizing questions. “Why does an animal live where it does?” “What is the nature of the ties that bind it to its world?”

One of the physical ties is especially interesting in this, our present period of earth history. It is a force that is omnipresent; no living thing is exempt from its influence. For life in the aggregate is lived within a relatively narrow range of temperature. The fact that our planet Earth has a fairly stable temperature helps to make it hospitable to life. In the sea, especially, temperature changes are gradual and moderate and many animals are so delicately adjusted that they cannot tolerate an abrupt or extensive change in the temperature of the surrounding water. If such occurs they must migrate or die.

Now our climate is changing and we are moving into a warm cycle of unknown duration. Ocean temperatures are slower to reflect the change than the air, but there has been a measurable warming of Atlantic coastal waters. The winter temperatures, which may be the critical ones for some marine animals, are less severe. Also, the water is warmer in summer. Records of winter temperatures for the Gulf of Maine (based on an average of records for Boston, Boothbay Harbor, Eastport, and St. Andrews) show an impressive rise. In 1918, for example, surface temperatures during the coldest month of the year averaged about 28°, and in the 1910–1919 decade, temperatures below 32° occurred almost every winter. During the 1930’s, however, in only three years of the decade did the water temperatures of the coldest month average below 32°, and this has not happened in any year since 1940. Last winter’s coldest month averaged 38°, or ten degrees warmer than the winter of 1918 – a very substantial increase as sea temperatures go.

It is not surprising that such a change in the oceanic climate should have caused many shifts of distribution among marine faunas. It is well known that the waters around Greenland and Iceland have been invaded by animals from regions to the south. This has been well documented in papers by Jensen and others. Less has been said about corresponding changes in the waters off the east coast of the United States. But many are occurring, and collectively they seem to form a significant picture.

Take, for example, the green crab. This is a member of the family of swimming crabs to which the blue crab also belongs. Once its range was very restricted. S. I. Smith, in Verrill’s report on the Invertebrate Animals of Vineyard Sound, gave its distribution as “Cape Cod to New Jersey.” More than a quarter of a century later, in 1905, Dr. Mary Rathbun placed its northward limit in Casco Bay. As late as 1930 she reported only one record of its occurrence east of Casco Bay. The 1929 biological survey of Mt. Desert Island did not include it. However, in 1930, two lots of green crabs were collected in the vicinity of Brooklin, in Hancock County, Maine. These were sent to the National Museum because they had been taken so far beyond the limits of their normal range. Nine years later, Leslie W. Scattergood [an FWS scientist of lobster culture] found the species at Winter Harbor, and in 1951 he was able to report its eastward spread to Lubec. A few months later he found it on the Maine shores of Passamaquoddy Bay, and Canadian biologists reported it from Oven Head on the eastern shores of this bay the same year. According to the Biological Station at St. Andrews, the green crabs were very abundant on all the flats of Passamaquoddy Bay in the summer of 1953, when they were also found across on the Nova Scotian shores – in St. Mary Bay in August and in Minas Basin in November. There the record stands for the moment. The spread of the green crab is better documented than that of most species for a practical reason. Its invasion of the soft clam areas of Maine has, in some localities, almost wiped out the industry, for the crab preys so extensively on the young stages that farming of clams can hardly be practiced in its presence.

However, there are other occurrences perhaps equally interesting. For these largely unpublished records I am indebted to a number of biologists, including various members of the Fish and Wildlife Service, John [N.J.] Berrill of McGill University, and Fenner Chace of the National Museum.

With warming water temperatures, the sea herring is becoming scarce in Maine. Whether this is entirely a matter of temperature or whether diseases or other factors enter the picture I suppose no one can say with assurance. But as the herring declines other fish, members of the same family but of more southern distribution, are moving in. Back in the 1880’s there was a substantial fishery for the menhaden at East Boothbay and some other Maine ports. Then the fish disappeared from Maine and for many years has been yielding enormous catches in New Jersey, Virginia, North Carolina, and other southern states. But about 1950 the menhaden came back into Maine waters in numbers, followed by Virginia boats and fishermen. Then there is another member of the same family, the round herring. In the 1920’s Bigelow [Henry Bigelow of Harvard University] and Welsh reported it as occurring from the Gulf of Mexico north only as far as Cape Cod. But it was rare anywhere on the Cape, and two that had been caught at Provincetown were preserved in the Museum of Comparative Zoology. Now, however, immense schools of this fish have been appearing in Maine waters for several years, and the fishing industry is experimenting with canning it.

There are negative responses, too. One of the hydroids, a member of the genus
Syncoryne
, is so delicately adjusted to water temperatures that it has been considered by some a key temperature-zone organism. Professor [N.J.] Berrill tells me that 6 years ago this species was common at Ocean Point, near Boothbay Harbor, in June. So was the hydroid
Clava.
But two years later, in 1950, Professor Berrill could find only a trace of
Syncoryne
, and since then none whatever, even in mid-winter. Apparently temperatures on this part of the coast have become too warm for it. The same appears to be true of
Clava
, of which none has been found during the past three years in the Boothbay region.

If we knew the whole story of each of these examples of a change of distribution we should very probably find the focus of our attention shifting to the larval stages of the animals that are involved. Often the adults might perfectly well be able to establish themselves in new areas outside of the normal temperature range of the species, but they cannot do so – that is, they cannot reproduce and have their young survive – because the waters are too cold or too warm for the welfare of the larvae. More and more it is becoming clear that the ecology of the adult marine animal is dependent upon the ecology of the larvae.

This fact is reinforced with beautiful clarity in another field of research, that has to do with the relations of the larval forms of some invertebrates to the substratum. This has been the subject of brilliant and significant work by Douglas Wilson at the Plymouth Laboratory.

Many invertebrates, as adults, live either permanently or semi-permanently attached to the sea bottom, where rocks are exposed, or burrow into its covering of sand or mud. If such sedentary animals are to establish new colonies, this must be done by the larvae, for they alone have freedom to swim or even to be carried passively in the currents. The minute and delicate larvae often have a further responsibility, for many species are so specialized that they can inhabit only a certain kind of sea bottom. Sand, for example, is far from being a substance of uniform nature. It is diverse in its geologic origin, its chemical nature, its capacity to support life. One of the small annelid worms from which Douglas Wilson has learned so much about the reactions of larvae lives only in clean, coarse sand, stirred by strong tidal action, and composed mainly of quartz with some intermixture of materials derived from rocks and shells. Such sand occurs only in scattered areas on the shores of the English Channel, and the occurrence of this species of worm is accordingly limited.