It would have to be a different location and context from those previously enjoyed. I couldn’t return to New Guinea to launch my endeavor. Work there would take me for months at a time away from Cambridge, where my duties at Harvard held me tightly. I had also begun experimental work on the social behavior of ants that required a well-equipped laboratory. They were proving too successful to abandon. Not least, I had a family now, Renee and our new daughter, Catherine.
How in the world could I explore an island wilderness while staying close to home? And if I found such a place, how could I turn it into a laboratory? There was only one way to solve the problem: miniaturize the system! Instead of relying on conventional islands the size of Krakatau, which are hundreds of square kilometers in area and usually have people living on them, why not use tiny ones, at most a few hundred square meters? Of course such places do not support resident populations of mammals, birds, or any other land vertebrates above the size of small lizards. Vertebrate biologists would not call them islands at all, even in a limited ecological sense. Yet they sustain large breeding populations of insects, spiders, and other arthropods. To an ant or spider one-millionth the size of a deer, a single tree is like a whole forest. The lifetime of such a creature can be spent in a microterritory the size of a dinner plate. Once I revised my scale of vision downward this way, I realized that there are thousands of such miniature islands in the United States, sprinkled along the coasts as well as inland in the midst of lakes and streams.
I thought I had the perfect solution. By exploring such places I would satisfy my emotional and intellectual needs. Working with insects, the organisms I knew best, I could conduct biogeographic research on an accelerated schedule. Succeed or fail, I would stay close to Harvard and my family.
In choosing the site of my laboratory, I preferred marine waters over lakes and rivers—strictly an aesthetic choice. I pored over maps of fringing islands all along the Atlantic and Gulf coasts, from Quoddy Head State Park in down-Easternmost Maine to the Padre Island National Seashore in southernmost Texas. I also studied charts of the small islands around Puerto Rico, still a relatively quick jet flight away. A decisive winner quickly emerged: the Florida Keys, if combined with the nearby northern islands of Florida Bay and the southwest mainland coast, seemed ideal. I turned to more detailed navigational charts and photographs for a closer look. The islands came in all sizes, from single trees to sizable expanses up to a square kilometer or more. They varied in degrees of isolation from a few meters to hundreds of meters from the nearest neighbor. The forests on them were simple, consisting in most cases entirely of red mangrove trees. And they were available in vast numbers. One sprawling miniature archipelago west of the Everglades bore the suggestive name Ten Thousand Islands. Almost all of them could be reached in a single day, if you started with an early four-hour flight from Boston to Miami, drove a rental car down U.S. I to the Keys, and finally took a short boat trip out to the island of choice.
In June 1965 I flew to Miami to enter my new island world. I was accompanied by Renee and Cathy—now twenty months old, walking, talking, and pulling down every movable object. For ten weeks I explored the small bayside mangrove keys from along Stock Island and Sugarloaf north to Key Largo. My spirits soared. I was back where I was meant to be! Each morning I pushed away from a marine dock in a rented fourteen-foot boat with outboard motor and moved out along the channels that had been cut through the mangrove swamps to the open waters of Florida Bay. I visited one islet after another, passing over turtle grass flats in water sometimes clear and sometimes, especially on windy days, milky white from the churned-up bottom marl. Once or twice a day I saw a distant fisherman or a powerboat moving to deeper water, but into the swampy archipelagoes of my choice few other people ventured. Less than a mile away U.S. I, which runs the length of the keys to their southernmost point at Key West, was choked by traffic. It was lined by a noisome thicket of motels, trailer parks, amusement parks, marinas, fishing tackle shops, and fast-food restaurants. But beyond hearing range of the rumble and whine of traffic, the swamps and islets were pristine, a virgin wilderness. Mangrove wood has little commercial value. No one but a naturalist or escaped convict would choose to traverse the gluelike mud flats and climb through the tangled prop roots and trunks of the mangrove trees. So I had it all to myself: one more time, a world I knew so well, more complex and beautiful than anything contrived by human enterprise.
I pushed into the interiors of the islets to examine the arthropod inhabitants. Sometimes the little forests opened at the center into a slightly raised glade carpeted with aerial roots and algal mats. Sometimes I found myself beneath the massed nests of clamoring herons, egrets, and white-crowned pigeons. I drifted along from landfall to landfall, collecting specimens, studying charts, filling my notebook with impressions. Mine was anything but a world-class voyage, but I was as content as Darwin on the voyage of H.M.S. Beagle. I ate lunch in the boat while peering over the side at rich marine life along the edge of the islets. Just beneath the reach of low tide, the mangrove prop roots were covered by masses of barnacles, sea squirts, anemones, clams, and green and red algae. Schools of mangrove snappers and young barracuda prowled in and out of the root interstices and alga-slimed cavities of the mudbanks. Should I have become a marine biologist? Too late to think about that now. I was at peace. The only sounds I heard were the call of birds and the slap of waves against the hull of my boat. An occasional jet droned high above, to remind me, you’ll come back, dreamer, your life depends on those artifacts you’ve tried to escape.
I found what I had come for in the mangrove islets. The trees swarmed with scores of species of small creatures: ants, spiders, mites, centipedes, bark lice, crickets, moth caterpillars, and other arthropods. Many flourished in breeding populations, prerequisites for the establishment of an experimental biogeography. And from one mangrove clump to the next, the species changed. For ants the pattern was consistent with competitive exclusion. Below a certain island size, the colonization of some species appeared to preclude the establishment of others. I saw an opportunity in the study of these telescoped patterns. Instead of traveling great distances from one Pacific Island to another to study the distribution of birds, an effort requiring months or years, I could, by guiding a fourteen-footer among the islets, analyze the distribution of arthropods in a period of days or weeks.
How, then, might these mangrove dots be turned into little Krakataus? I saw no easy way, and cast about for some alternative approach. I made the following decision: continue with the mangrove studies, but in addition select other islands lacking trees in order to make sterilization easier. I had learned that treeless sandy islands in the nearby Dry Tortugas are occasionally flooded and swept clean of their low scrubby plant growth by hurricanes. If I could monitor them before and after a big storm, I might observe the recolonization process and establish whether it created an equilibrium. Let the Caribbean’s stormy weather be the volcano. At least it was worth a try.
I called on William Robertson, official naturalist of the Everglades National Park, to explain my idea. Bill frequently visited the Dry Tortugas to study sooty terns, a far-ranging species that nests on this remotest of Florida’s archipelagoes. He agreed that the procedure might work, and invited me to join his research party on the next boat trip out from the docks at the Everglades town of Flamingo to survey the area. Once settled in dungeonlike rooms at Fort Jefferson, the old Federal stronghold and prison on Garden Key, we took a smaller boat out to the other, smaller islands of the Dry Tortugas. I leaped into the surf and scrambled onto each of the little sandy keys in turn, making a record of the sparse vegetation and arthropods. My notebook was soon complete. All I had to do now was wait for a serious hurricane to pass over in order to begin a study of recolonization.
Providentially, from a biologist’s possibly perverse point of view, two hurricanes struck the Dry Tortugas during the next ten months. Betsy, on September 8, 1965, threw gusts up to 125 miles per hour at Fort Je
fferson. The milder Alma attained gale force winds on June 8, 1966. Between them they wiped the vegetation off the smallest sandy islands, as I had hoped. By that time, however, I had changed my plan and advanced to a bolder scheme. Why be confined to the haphazard distribution of a few remote keys? And why depend on the passing of hurricanes, which normally strike the Dry Tortugas only once or twice every ten years? The method was in any case not fully experimental. It could not be controlled. Instead, I thought, why not select ideally located mangrove keys from among the hundreds near U.S. I, then fumigate them with pesticides? It should be possible to kill off all the insects and other arthropods. These islets could be chosen to represent different sizes as well as various distances away from the mainland. Other islets, left unfumigated but otherwise studied in identical fashion, might serve as controls.
At this point, the fall of 1965, Daniel Simberloff joined me as a collaborator. The added vision and inspired effort of this second-year graduate student made it possible to turn the mangrove keys into a laboratory. Dan was primed for an effort of this kind. While an undergraduate at Harvard he had majored in mathematics, graduating magna cum laude. He could have moved on easily to a successful career in mathematics or the physical sciences. But after taking Natural Sciences 5, the famous nonmajors course in biology given by George Wald, he decided this branch of science was more to his liking. During his senior year he interviewed Bill Bossert and me and asked: Is graduate study in biology feasible if one has a stout heart but thin undergraduate training in that subject? Indeed it was, we both responded, especially for a mathematician. If you enter population biology now, the new discipline will reward skills in model building and quantitative analysis. All you need to do is add an all-out effort in biological training.
Simberloff began his Ph.D. study under my sponsorship in the fall of 1964. I hesitate to use the usual expression “studied under me,” because in the years to follow I learned as much from him as he did from me. We soon became partners.
Dan at least looked as though he could manage field biology. With somewhat hawkish features, a solid muscular body carried in a relaxed slouch, he might have passed for the kind of Ivy League quarterback who studies calculus or Chinese history too conscientiously to be an athletic star. Like many bright students of the day he was also a leftist radical, of the thinker rather than activist subspecies, suspicious of all authority and fierce enough to be a supporter of Eldridge Cleaver for President. This was quite all right with me. In 1965 the civil rights movement still meant idealism and courage tested on the dangerous back roads of Mississippi. The mere mention of Cuba, recently the site of history’s only nuclear confrontation, chilled us both; and the war in Vietnam was slowly gathering momentum. The Florida Keys were bracketed by bases at Homestead and Key West, and the whole area hummed with military activity. That summer I saw my first Green Berets, a platoon riding through the streets of Key West in a troop carrier. My admiration for the military and my vaguely centrist political beliefs were yielding somewhat to uneasiness over the direction the country was headed. Soon Dan and I began to share acerbic jokes about Lyndon Johnson. We watched in resentment as helicopters flew overhead, bearing commanding officers from ships to their homes ashore. We perched on the branches of mangrove trees, collecting spiders and crickets, on a nearly invisible budget, trying to learn how ecosystems are assembled. A dozen helicopter rides would have paid for our entire project. But not one citizen in a hundred would have understood what we were trying to do. It was a time of massive imbalance in favor of military security over environmental security. We had no idea how or when the differential might be redressed, nor did we expect ever to see ecology given national priority as a science. We were just thankful for the opportunity provided us by modest funding from the National Science Foundation. And thankful just to be there, in this beautiful natural environment.
By joining the project, Dan took a career risk. Our endeavor had an uncertain future, because no one had previously tried or even conceived anything like it. If we were unable to eliminate the arthropods completely from the islets, we would be in trouble. If we failed to put scientific names on the myriad of species we found on the islands, our data would be far less valuable. If the colonization of the sterilized islands took ten or twenty years or longer to progress significantly, Dan would have to find other work to complete his Ph.D. thesis. Graduate students were expected to finish their degree requirements, including a complete and reasonably well polished research thesis, in no more than six or seven years. Most accepted low-risk projects, those new enough to generate significant results but close enough to preexisting knowledge and proven techniques to be practicable. Simberloff had none of these assurances. In September 1965 he nonetheless departed for the Florida Keys, with the initial task of selecting the experimental islets.
In the months that followed we divided the labor further. While Dan grew lean and acquired a deep tan laboring on the open waters of Florida Bay, I attended to the administration of the project. The details of my own role ranged from the unusual to the bizarre. For an effort of this kind we had first of all to engage the services of a professional exterminator. Fortunately, there was an abundance of companies in Miami. The executives of the first two I called answered with rich southern accents and clearly thought I was either joking or crazy. On the third try I got Steven Tendrich, vice president of National Exterminators, Inc. He had a northern accent, which gave me hope. Could he manage, I asked carefully, to spray clumps of mangrove in the Florida Bay with short-lived insecticides that would remove all the insects? We would ourselves eliminate by hand the tree snails and other larger animals that might be resistant to the chemical. Tendrich did not hesitate. He said yes, maybe he could do a job like that. Sure, give him some time to study the logistics. But even if it looked promising, he warned, he could not manage much in the field until the fall, when the heavy business of summertime Miami slacked off.
Progress in this sector having been achieved, I went with Simberloff to visit Jack Watson, the resident ranger of the National Park Service, to ask his permission to exterminate the whole faunas of islets. Most of the candidate islets were within the boundaries of the Everglades National Park and Great White Heron National Wildlife Refuge, over which he had partial jurisdiction. Obtaining permission to wipe out animal populations on federally protected land may sound like an impossible dream, but it proved relatively easy. Watson gave it without hesitation, asking only that we keep him briefed. Bill Robertson, our principal contact in the Park Service, was also in sympathy with the rationale and plan of the project. He knew that the targeted islets were no more than clumps of red mangrove among hundreds scattered through Florida Bay. They harbored species or races no different from those abounding elsewhere. We assured Watson and Robertson of our intent to protect the vegetation, and our expectation that the trees would be fully recolonized with insects and other arthropods following the “defaunation,” as we now called it. The experiment, Simberloff and I argued, might provide information that would help guide future park management policy. Our earnestness proved persuasive, and we never faced opposition from government officials or the public.
Finally, I set out to contact specialists who could identify the species of insects and other arthropods living on the mangrove islets before fumigation and while the recolonization proceeded. This proved the most difficult task of all. There were at most several hundred entomologists in the United States able to identify insects from the Florida Keys. Their study would be complicated by the fact that many of the creatures we expected to find are immigrants from the West Indies, especially nearby Cuba and the Bahamas. Among our discoveries were to be the first specimens of the tropical spider family Hersiliidae recorded in the eastern United States and several large and striking long-horn beetles previously known only from the Bahamas. In the end we were able to persuade fifty-four specialists to assist us in the classification of our specimens. Most pitched in with enthusiasm. An expert on spiders, Joseph Be
atty, went so far as to visit Simberloff in the field to assist with the on-site identification of the colonists.
During the spring of 1966 Simberloff reported in with his recommendation of islets that seemed well placed either for defaunation or to serve as controls. We began surveys prior to spraying by inspecting every square millimeter of trunk and leaf surface, digging into every crevice, prying beneath flakes of dead bark and into hollow twigs and decaying branches. We collected every species of arthropod we found. Later, after the defaunation, Dan took over the heavy duty of regular monitoring. To disturb the colonists as little as possible, he relied on photographs and his own growing familiarity with the mangrove fauna. It was hard and uncomfortable work, demanding the combined skills of insect systematist, roofer, and restaurant health inspector. Simberloff, the city-bred mathematician, did well. He endured the insect bites and lonely hours in the hot sun I had promised him. Once, after his outboard motor failed, he spent the night on one of the islets, managing to escape only when he hailed a passing fisherman the following morning. Exasperated with the gluelike mud through which we had to wade to reach several of our islands, he built a pair of plywood footpads shaped like snowshoes and drilled holes in them to reduce suction when they were lifted. When he tried them out he sank to his knees and had to be pulled out by me and another companion. I called the invention “Simberloffs” afterward. Dan was not noticeably amused.
I joined him at intervals to give assistance. On one memorable occasion—June 7, 19605—Dan met me at the Miami International Airport just as Hurricane Alma was churning up the central Caribbean in the general direction of Florida. A storm watch had been posted for Miami and the keys. When we awoke the next morning the sky had clouded over, wind was picking up from the south, and a light rain had begun to fall. The eye of the storm was expected to pass up the west Florida coast and sideswipe Miami. Here, I thought, was a rare opportunity to watch a hurricane disperse animals out of the mangrove swamps and across the water. Travel in high winds seemed a likely means of colonizing the little islands. I suggested that we stand inside a nearby mangrove swamp during the storm and watch for animals blown along by high winds. For some reason that escapes me now, I didn’t think much about danger to ourselves. Simberloff agreed without hesitation. All right, he said, something interesting might happen. Good enough.
Naturalist 25th Anniversary Edition Page 24