The Ivory Soap Bomb and the Isthmus

After two years of waiting for the canal cratering experimental program to begin, the Anderson Commission received the wonderful news in January 1968 that President Johnson had finally permitted the 2.3-kiloton Cabriolet shot to proceed at the Nevada Test Site. Because radioactive fallout might escape into the atmosphere and contaminate the local milk supply or cross the border to cause an international incident, the timing had to be precise—after the State of the Union address, but before the Nevada grazing season. In a stroke of good luck for the advocates of Plowshare, the winds on the day of the test blew away from Mexico, and a snowstorm prevented debris from reaching Canada in detectable amounts.8

Although the Cabriolet test created a crater of only 360 feet wide and 120 feet deep, a follow-up experiment in March generated exciting results for proponents of the nuclear waterway. Project Buggy, a simultaneous detonation of five nuclear explosives (spaced 150 feet apart at a depth of 150 feet), produced what Representative Chet Holifield of the Joint Committee on Atomic Energy called a “miniature-size canal in the Nevada desert” (300 feet wide by 80 feet deep by 900 feet long). His assessment of the situation as “very hopeful, very promising” renewed calls to amend the Limited Nuclear Test Ban Treaty “to reconcile it with common sense.”9 More favorable publicity appeared in news reports that fallout from both shots occurred only a few hundred yards from the craters, and that no radiation could be detected three days afterward, unlike earlier tests. An unnamed AEC source attributed the smaller amount of radiation to the “really tiny fission device” used to trigger the thermonuclear explosive. For the “friends of Plowshare,” the 97 percent fallout-free device—dubbed the Ivory Soap Bomb—offered great reassurance: “We’ve been talking about doing it for years, but now we could really get down and dig a second Panama Canal with atomic explosives.”10 The long political delays had served their purpose of giving the science and technology of PNEs time to catch up with expectations.

Or so it seemed. Such rhetoric discounted the continuing opposition by Latin Americans to the use of nuclear explosives on their lands. Panamanian ambassador Jorge T. Velasquez, who called instead for expanding the existing waterway, announced, “We know that experiments have not shown there is control over the dangers of atmospheric and underground radioactivity, nor the practical possibility of this technique in the construction of a sea-level canal.”11 Not only were the AEC’s assurances about clean PNEs wearing thin, so was the techno-economic rationale for building a second waterway. The U.S. Navy’s largest ships needed to be able to cross the isthmus as quickly as possible, but that was not the case for an emerging class of commercial vessels. In 1966, massive new tankers, some capable of carrying 2.2 million barrels of crude oil from the Middle East to Europe, had already begun bypassing the Suez Canal to save on tolls; voyaging around the Cape of Good Hope took longer, but the size of their cargoes made up for the loss of time.12 That same year, the burgeoning Japanese shipbuilding industry completed a 215,000-ton tanker capable of drawing fifty-six feet, which exceeded the Panama Canal’s maximum channel depth of forty feet, and analysts predicted that tankers of 500,000 and even 1 million tons would soon be feasible.13 The global shipping industry was changing in ways that demonstrated the need for the Panama Canal to adapt or else become a mere monument to a bygone era—but that also undercut the long-standing arguments for a sea-level channel.

As the Anderson Commission’s economic advisors tried to predict future shipping trends, the Route 17 geological consultants delivered unwelcome news. Drilling samples verified that about half of the route, a twenty-mile stretch in the Chucunaque valley, crossed land whose bedrock consisted of clay shales (rather than basalt, the much harder material underlying most of the Continental Divide, the assumption of which had underpinned the 1964 selection of routes). Nuclear explosives would likely not form stable slopes in such an unstable medium, meaning that achieving the shallow slopes needed to prevent the crater from collapsing over time would require conventional excavation techniques.14

Clay shale happened to be the same type of sedimentary rock that had caused destructive landslides during the construction of the original Panama Canal, and thus the problem was not a surprise to engineers familiar with the physics of the isthmus. As one of the leaders of the Army Corps of Engineers’ Nuclear Cratering Group explained at the March 1968 commission meeting, “The original thinking was that if we ran into a bad actor like clay shale along the routes, we could approach it from a conventional excavation standpoint.”15 However, the prospect of bulldozing such a large area undermined the financial advantage PNEs had offered in the first place.

While engineers consulted with leading soil mechanics specialists to determine whether the geological discovery really did rule out PNEs, the Livermore physicists conducted chemical explosive experiments to try to model the effects of burying thermonuclear devices in wet clay shale. John Kelly of the AEC’s Division of Peaceful Nuclear Explosives later even discussed the matter with his Soviet counterparts, who insisted it was not a problem.16 A few days after the March 1968 CSC meeting at which the issue was first unveiled, commission member Milton Eisenhower vented his frustration in a private letter to Executive Secretary Sheffey that the group’s most vociferous member, Raymond Hill, already appeared ready to abandon Route 17: “When we began our deliberations, we were enthusiastic about atomic construction. Now we are on the verge of deciding that, largely because of possible conditions of soil instability, atomic excavation is not practical . . . I don’t want to be drawn inexorably to route 10 and a sea-level canal by traditional construction methods . . . merely because his expert opinion points in that direction.”17 Route 10 referred to a new potential seaway site about ten miles west of the existing canal, to which the commission had begun devoting attention in the fall of 1967 as an alternative to the nonnuclear option of converting the existing canal.18

If nuclear excavation of Route 17 was no longer possible, then that had major implications for future U.S.-Panama treaty negotiations. The 1967 draft treaties had established the U.S. commitment to building the sea-level canal in Panama and had granted Panama the right to veto nuclear methods. However, as outsider analysts explained, if the existing waterway continued its descent into obsolescence, and if PNEs constituted the only financially feasible means of constructing a new passage, then Panama would pretty much have to agree to a U.S.-built nuclear canal.19 To preserve the U.S. upper hand in future negotiations, how much should the commission reveal about the clay shale problem?

The deadline for the fourth annual report, covering the period from July 1, 1967 to June 30, 1968, was approaching, and it would be the last one prepared for President Johnson, who had decided not to run for reelection. The previous three reports had already erred on the side of vagueness, and thus to mollify the commission’s critics while preserving as much U.S. leverage as possible, Sheffey recommended a selective, semitransparent approach: it should “start surfacing some of the problems we foresee and not catch the Congress by surprise when the final report comes in. The problem is that we don’t want to disclose things that will handicap treaty negotiations in the future by our action.”20 But reconciling such opposing goals proved impossible. In conveying the ensuing report to Congress, President Johnson omitted the clay shales matter from his public statement, and sent mixed messages by emphasizing both the benefits of the conventional Route 10 and the favorable results of the two 1968 Nevada Test Site shots.21 He also overlooked another unwelcome issue consuming more and more of the commission’s attention: regardless of the method used to cut the channel, what would happen once the flora and fauna of the two oceans reunited after a few million years of evolutionary separation and speciation?

Marine and Evolutionary Biologists Barge In

The secretary of the Smithsonian Institution, Leonard Carmichael, had posed a version of this question to AEC director Glenn Seaborg back in the spring of 1963, when U.S.-Panama tensions, the resumption of nuclear testing, and the negotiations over the test ban treaty generated widespread publicity for the Panatomic Canal idea.22 Carmichael had likely been prompted by an employee of the Museum of Natural History, oceanographer I. Eugene Wallen, who had spent years studying the faunal effects of nuclear testing in the South Pacific.

Carmichael wound up dropping the offer to help conduct baseline taxonomic and ecological research along the proposed canal routes, but his successor, ornithologist S. Dillon Ripley, saw a great opportunity (fig. 5.1).23 Determined to improve the Smithsonian’s waning reputation for biological excellence, Ripley reestablished contact with the AEC in the summer of 1964.24 Later that year, days after President Johnson announced the sea-level canal plans, Wallen submitted a $2 million proposal “to determine the potential damage by canal construction to the populations, distributions and abundances of marine and terrestrial organisms on the two proposed routes” in Panama and Colombia.25 However, the AEC chose the Battelle Memorial Institute, a private organization that in turn subcontracted with university-based teams.26 Deeply disappointed, Wallen and Ripley regrouped to consider their options.27 One of the veterans of the Chariot affair, AEC Environmental Sciences Branch chief and plant ecologist John Wolfe, provided an encouraging boost: “In such massive engineering proposals,” he wrote Wallen in reference to the sea-level canal, “biology is no longer a flower girl, she’s the bride.”28

For Ripley, the canal feasibility studies held the promise of attracting new funds not only for the Museum of Natural History, but also for one of the Smithsonian’s far-flung research facilities. Decades earlier, in 1937, he had visited Barro Colorado Island (BCI) in Panama’s Canal Zone while voyaging from Philadelphia to New Guinea for a zoological expedition.29 BCI was an artifact of the construction of the canal, as the reservoir created by Gatun Dam left only the highest hilltops of the Chagres River valley unsubmerged. The island was also a testament to the Smithsonian’s embrace of the isthmus as a model study site, beginning with the prescient 1910–12 biological survey of the Panama Canal Zone, which generated several studies documenting the area’s marine and terrestrial biota.30 The survey led the governor of the Canal Zone to designate BCI a reserve in 1923, and over the next two decades, the research station drew more scientific visitors than any other tropical research facility.31 BCI and the associated Canal Zone Biological Area (CZBA) became a Smithsonian bureau after the war and by the late 1950s had provided the setting for hundreds of articles on tropical forest biota and dynamics. However, the CZBA lacked facilities for long-term terrestrial and marine research. Expanding the institutional base of tropical biology gained urgency as tropical nations decolonized and sought to accelerate deforestation for development.32

Another influential source of encouragement for expanding the CZBA was Ernst Mayr, an old friend of Ripley and fellow ornithologist, the head of Harvard’s Museum of Comparative Zoology, and the mentor of BCI director Martin Moynihan. Mayr had gained fame in the 1940s as a proponent of the Modern Synthesis of evolutionary biology and the concept of allopatric (geographic) speciation, a topic for which the Panamanian isthmus provided an ideal research setting.33 Knowing the approximate period of the geological emergence of the Central American land bridge made it possible to date the origin of evolutionary differences between marine species on either side of the isthmus.34 The 1910–12 Smithsonian survey had built upon a few pioneering studies to expand knowledge of the marine fishes of the Atlantic and Pacific coasts and associated evolutionary effects of geographic isolation.35 Naturalists subsequently documented some other taxonomic groups west and east of the isthmus that appeared similar but were not identical, as Mayr substantiated for shallow-water sea urchins in a foundational paper that called for more research on modes of speciation in marine organisms. But like several other such researchers, he based his results not on a visit to the biogeographical barrier in question, but rather on an earlier taxonomist’s work.36

Mayr’s recognition of the evolutionary importance of the Central American isthmus shaped his mixed reaction to President Johnson’s December 1964 announcement. As he expressed to a colleague on the President’s Science Advisory Committee, the consequences of conjoining two distinct oceans raised daunting questions beyond the issue of radioactivity:

I have been worrying for some time about the contemplated sea-level canal across the Isthmus of Panama. There is little doubt that such a salt water connection between the two great oceans will have many and drastic effects on the marine faunas and floras. There are closely related species living on either side of the Isthmus and no one can predict with certainty what will happen if such species come in contact with each other. Will one wipe out the other, or will it hybridize with it? How many disease organisms will be carried from one ocean into the other? What will the tidal currents do in the canal? Will the inflow of the more silty waters of the Pacific damage coral reefs on the Atlantic side? I do not know what the situation is in commercial fisheries, and other utilisation of marine organisms, but . . . I am sure that the opening of the canal will produce many problems, and world science would never forgive us for not being prepared for such eventualities.37

In addition to expanding marine stations in Panama, Mayr argued the United States should appoint a board to oversee the research needed to answer such questions, perhaps involving the National Academy of Sciences. In this regard, he noted, “I might add parenthetically that organismic biology is, on the whole, poorly represented on high level boards in Washington. This is not injurious in most instances, but it may lead occasionally to the neglect of an important problem, as I believe is the case with respect to the Panama Canal.”38 Mayr’s aside was more than parenthetical, for he had been promoting organismic biology as a means of counteracting the growing dominance of molecular approaches to the life sciences.39 Also, conservation was not a prominent theme of his career, though he had published a few articles decades earlier about bird protection.40 Mayr’s interest in both the ecological risks and research opportunities of the proposed waterway spoke to the spectrum of positions among the biologists who would play major roles in the sea-level canal story.

Mayr had an important informant who helped shape his thoughts about the sea-level canal—his recent graduate student Ira Rubinoff. During visits to the CZBA in 1961 and 1962, Rubinoff had begun collecting and breeding fish from the Caribbean and Pacific coasts to delineate evolutionary divergence in species separated by the isthmus. Conducting such research in the Canal Zone entailed unusual occupational hazards, from having to pass checkpoints manned by surly sentries to missing optimal tides due to the lack of gas stations that serviced military vehicles on weekends.41 But the Canal Zone provided protection and amenities for North American and European researchers, and the efforts to expand the CZBA paid off in 1965, when Moynihan secured leases with the U.S. military for two Atlantic and Pacific marine stations, the Smithsonian hired Rubinoff as assistant director for marine biology, and Congress raised the appropriation from the original $10,000 to $350,000.42 Ripley announced the name change to Smithsonian Tropical Research Institute (STRI) the following year.43 As STRI’s marine director, Rubinoff provided an energetic on-the-ground complement to the D.C.-based Smithsonian campaign of Ripley, Wallen, and Assistant Secretary for Science Sidney Galler, a former Office of Naval Research biologist.

In July 1965, Rubinoff published the first article on the sea-level canal’s potential nonradiological effects, the Natural History essay that likely caught Irwin’s attention.44 Several outcomes seemed possible, including large-scale extinctions, as suggested by principles of ecology and genetics, morphological comparisons of Caribbean and Pacific shore fishes, and historical human-facilitated introductions of organisms to new areas. Dutch elm disease and the Australian rabbit invasion were infamous in the annals of pest outbreaks; other cases like the canal-facilitated migration of voracious Atlantic sea lampreys into the U.S. Great Lakes were less well known but equally devastating to local ecosystems and fishing-based communities. Rubinoff assured readers that the sea-level canal would “not provide every species with a free pass to a new ocean.” But why leave anything to chance? A strategic research program such as that of the International Indian Ocean Expedition, one of several large-scale geophysical initiatives of the Cold War era, would begin to demystify the uncertain effects of marine faunal mixing.45

Risky Mix

Scientific conferences provided an important venue for addressing the sea-level canal’s ecological and evolutionary consequences. At the 1965 International Conference on Tropical Oceanography in Miami, Rubinoff and oceanographers from other distinguished institutions discussed the importance of expanding the preproject studies beyond radioactivity in the food chain, and marveled at what they considered the myopia of attendees from the Battelle Memorial Institute and other AEC subcontractors.46 However, in the spring of 1966, Battelle Memorial Institute officials invited Galler to their Ohio headquarters to discuss the “myriad problems” that had become apparent as they realized the limitations they faced in fulfilling their AEC obligations.47 Galler convinced the Battelle managers to invite the Smithsonian to cosponsor an international symposium aimed at developing a long-term ecological survey for the Canal Study Commission.48

Planning the symposium required a great deal of strategizing.49 In August 1966, Galler convened a meeting at the Museum of Natural History of all the relevant organizations: Battelle (represented by radioecologist William Martin), the AEC’s Division of Peaceful Nuclear Explosives (John Kelly) and Environmental Sciences Branch (John Wolfe), and the Army Corps of Engineers and CSC (jointly represented by Harry Woodbury).50 The group, which also included representatives of the American Institute of Biological Sciences and the Organization of American States, discussed the task force’s draft proposal for a $6 million five-year precanal marine survey, and agreed that holding an international symposium of tropical biologists in Panama would help identify and publicize the top canal-oriented research priorities.

However, sharp differences emerged regarding questions of framing and language. Pointing to a section of the draft that drew on Rubinoff’s hybridization studies of Atlantic and Pacific fish, Woodbury noted that agricultural scientists “devote their lives to developing hybrids.” Moreover, because some of the transisthmian species liable to go extinct might be “those we would want to exterminate,” attention should also be devoted to the beneficial environmental changes that the canal might effect. When a Smithsonian employee explained that only by accentuating the negative would Congress respond with the needed funds, Woodbury stated that using words like “catastrophe” and “profound disturbance” would upset his bosses, who had been tasked with determining where—not whether—to build the sea-level canal.51 Colonel Sheffey of the CSC likewise argued in a follow-up letter that the task force dwelled too much on “unfavorable ecology changes.”52 Galler tried to smooth things over by saying it was just a draft, but the exchange revealed the fine line between courting and alienating the oversight agencies.

The Smithsonian team also recognized the importance of “not antagonizing the Panamanians,” and thus they invited both U.S. and Panamanian representatives to the symposium slated for November 1966. They also emphasized the goal of advancing basic ecological research.53 Yet the sea-level canal featured prominently in the discussions of the four-day symposium (attended by sixty North American and Latin American biologists) and in the ensuing write-up for BioScience.54

Allocating internal resources to stage the Panama conference and relevant pilot projects at STRI became an important part of the Ripley team’s evolving strategy to create, in Galler’s words, “a receptive constituency” among the scientific and governmental communities to fund the Smithsonian’s long-term program.55 Smithsonian research awards enabled the husband-and-wife team of Ira and Roberta Rubinoff to focus on interoceanic colonization and isolating mechanisms in Atlantic and Pacific fish populations.56 Such grants also made it possible for visiting marine biologists to conduct research at STRI’s new facilities on the Caribbean and Panama Bay coasts, resulting in publications that would drive much of the sea-level canal debate.57

The Smithsonian’s self-funded canal studies also benefited marine scientists on the other side of the globe. In early 1967, STRI joined the Hebrew University of Jerusalem to investigate Red Sea and eastern Mediterranean biota. The hundred-mile-long Suez Canal, completed in 1869, had a high-salinity interior that blocked most, but not all, species’ migration between the Red Sea and Mediterranean.58 The Smithsonian–Hebrew University initiative made the most of a new U.S. program to apply excess foreign currencies generated by the sale of agricultural surpluses toward Smithsonian research in excess-currency countries, and Israeli scientists gained full access to the Suez in June 1967 following the Six-Day War.59 Israeli marine biologists made major contributions in the ensuing decade to the study of Red-Med species exchange, cleverly dubbed “Lessepsian migration” after Ferdinand de Lesseps, the architect of Suez and the failed 1880s-era Panama Canal.60 Biogeographic studies of the Suez Canal provided an important and disputed point of comparison and contrast for researchers endeavoring to predict the ecological and evolutionary effects of the Central American sea-level waterway.

The Panama conference seemed to be a major stepping stone, as exemplified by the warm letters exchanged afterward by Ripley and Woodbury, who had jokingly referred to himself in his presentation as a “devastation engineer.”61 Throughout 1967, Smithsonian and CSC representatives corresponded and met on occasion in Washington to discuss how to acquire $10 million for a decade-long Smithsonian-directed ecological program.62 Yet despite numerous presentations on the topic to House and Senate appropriations subcommittees, Galler complained, “Congress thinks of the SI primarily as a museum of public exhibits.”63 Even so, by early 1968, the tide seemed about to turn, as Smithsonian personnel prepared new proposals for consideration by several public and private organizations.64

The Smithsonian’s target constituency for canal ecology fundraising did not include the public, but mainstream attention to the nonnuclear dimensions of the sea-level canal was increasing at the time Galler made his confident prediction. At the December 1967 meeting of the American Association for the Advancement of Science in New York City, LaMont Cole, the president of the Ecological Society of America, asked the shocking question, “Can the world be saved?” His speech invoked the sea-level canal as one of several examples of human technological folly, and appeared in both BioScience and the New York Times Magazine. For the Smithsonian scientists, however, his focus on radioactivity and his erroneous claim that the Pacific Ocean stood higher than the Atlantic by an average of six feet, evinced the importance of advancing a more informed debate.65

To that end, in August 1968, Rubinoff published an article in Science with the provocative lede, “An opportunity for the greatest biological experiment in man’s history may not be exploited.”66 The article expanded on the earlier Natural History piece by quoting from the English ecologist Charles Elton’s 1958 book The Ecology of Invasions by Animals and Plants to discuss “ecological explosions” of noxious, nonnative species. New York’s Erie Canal, and later Ontario’s Welland Canal, had enabled predatory Atlantic sea lampreys to spread throughout the Great Lakes, decimating the commercial fisheries.67 Yet even such extensive losses, along with those inflicted in the United States by Japanese beetles, gypsy moths, fire ants, and chestnut blight, would likely be dwarfed by the sea-level canal’s unleashing of “mutual invasions of Atlantic and Pacific organisms [which] should be much more extensive, numerous, and rapid.”68

The article drew not only on historical case studies but also on the Rubinoff laboratory’s experimental research. To test the possible consequences of interbreeding between formerly isolated populations, Rubinoff and his collaborators, including his spouse Roberta Rubinoff, conducted mating experiments between Atlantic and Pacific marine gobies. The range of results regarding the viability of the offspring, and the broader question of which species might dominate, hybridize, or go extinct, demonstrated the need for extensive knowledge of the morphological and behavioral characteristics of the organisms in question, as well as their degree of genetic divergence over time. Moreover, according to well-established ecological principles regarding competition between species for the same resources, the struggle for existence would inevitably drive some organisms to extinction; the changed physical conditions induced by the sea-level canal would also disrupt long-standing population dynamics. Because the seaway would extinguish many species that might not ever have been collected and described by scientists, a preproject inventory would provide “a potentially important historical base for biological oceanography of the future.”69

Rubinoff closed the article by quoting from a 1963 speech that President John F. Kennedy had delivered to the National Academy of Sciences in celebration of its one hundredth anniversary. Two weeks after signing the Limited Nuclear Test Ban Treaty, Kennedy used the academy event to announce his intention to minimize government secrecy and thereby foster greater discussion by the international scientific community about proposed large-scale development projects. Furthermore, he warned that while “the problem of conservation” had previously entailed the destructive use of natural resources, “science today has the power for the first time in history to undertake experiments with premeditation which can irreversibly alter our biological and physical environments on a global scale.”70 Along these lines, Rubinoff called for the government to provide the support needed to quantify and predict the biological effects of the proposed sea-level canal, and to establish an independent, multidisciplinary “control commission for environmental manipulation” to regulate all proposed megaprojects.71 In important ways, he echoed the drafters of what would become the U.S. National Environmental Policy Act of 1969, the groundbreaking law requiring preliminary environmental impact assessments of federally funded projects.72

Rubinoff tried to leverage what would now be called a “traction opportunity” to advance both a specific research program and a more environmentally sensitive approach to development and policy-making.73 However, all the organizations that he and Smithsonian leadership approached, including the Ford Foundation, National Institutes of Health, Office of Naval Research, Air Force Office of Scientific Research, and Naval Oceanographic Office, turned down the proposal for a decade-long precanal investigation.74 Many complex reasons accounted for the unwillingness of public and private organizations to commit to such an ambitious research endeavor. Throughout the twentieth century, the institutional status of naturalist-based disciplines such as taxonomy, biogeography, and evolutionary and ecological science lagged further and further behind the more reductionist, experimental life sciences, as epitomized by molecular biology. Moreover, grant programs for ecology tended to focus on short-term, small-scale studies in places far from human influence.75

Rubinoff’s work also challenged persistent attitudes about marine resilience and invulnerability to human-mediated change. Not until the 1990s and early 2000s did funding agencies begin devoting serious attention to ocean conservation science. A terrestrial bias also permeated the agenda of the emerging environmentalist movement. Fears of marine species migration and mixing did not fit the agenda of potential allies who focused on the terrestrial threats posed by synthetic chemicals, rapid population growth, overconsumption, and other toxic byproducts of technological modernity. And even though oil spills and overhunting presented obvious dangers to fish and marine mammals, competition from nonnative introduced species was much harder to comprehend, for both mainstream scientists and environmental advocates.76

Indeed, the late 1960s was still an era of intentional aquatic species introductions. For over a century, governments and acclimatization societies in search of cheap protein or recreational opportunities had shipped live fish and shellfish for transplanting in rivers and bays around the world. Pests often moved with the desired species, resulting in occasional warnings, most famously from Elton, who described oysters as the “sessile sheep” of the sea.77 Nevertheless, government officials stocked Lake Michigan with Pacific salmon in 1966 and replaced France’s adopted oyster, the Portuguese Crassostrea angulata, with the Japanese C. gigas from 1971 to 1975.78 Although a reckoning with the ecological costs of such actions was dawning on biologists, questioning the wisdom of transplanting aquatic species still flew in the face of a hundred years of scientific advice.79

Another difficult thing to explain pertained to the existing Panama Canal’s failure to facilitate disruptive marine species exchange. As Elton had observed in the sole marine chapter of The Ecology of Invasions by Animals and Plants, “accidental carriage in or on shipping, that is in water ballast tanks or on the hull, has been a powerful and steady agency dispersing marine plants and animals about the world.”80 Yet thousands of ships had transited the Panama passage since 1914, and only one ocean species, the euryhaline Atlantic tarpon, had ever appeared capable of breaching the fresh waters of Gatun Lake.81 Of course, identifying invasive species required consistent monitoring as well as thorough knowledge of the native organisms of each coast. The Rubinoffs had recently discovered breeding populations of an Atlantic goby in the brackish Miraflores Third Lock Lake near the Pacific side, which suggested that further surveying might identify additional “successful amphi-American migrations.”82

The CSC had thus far maintained cordial relations with the Smithsonian in the joint initiative to expand federal funding of nonradiological research, but in the fall of 1968, Executive Director Sheffey penned a letter to the editor of Science taking issue with Rubinoff’s article. The commission was already funding studies to delineate the seaway’s possible biological consequences, and besides, marine organisms could already transit the Panama Canal via three methods: by swimming and drifting through the locks and freshwater interior, by clinging to the sides of ship hulls, or by being swept up into the ballast tanks of ships on one side and then released on the other. Biotic exchange must thus already be occurring on a large scale, without any ill effects. While a sea-level waterway might permit larger swimming and drifting biota to pass through, asserted Sheffey, “the area of danger of harmful biological changes when the oceans are joined is much less broad than it first appears.”83

Sheffey’s attitude reflected the conventional wisdom of the shipping industry, that maritime transportation had already mixed the world’s marine biotas and that any resulting biological harm was only localized—and more than offset by the enormous economic benefits of global shipping. Rubinoff responded to Sheffey’s letter that too little evidence existed to support his claims, and that he sought not to cause alarm but rather “to provoke action by the scientific community to predict the probable results of permitting two separate biotas to merge, and to measure such changes as may occur when and if the canal is dug.”84 Such careful language reflected the difficulty of reconciling the worldviews of hydro-engineers and scientists, and of meeting traditional expectations of scientific objectivity amid the environmental policy-making upheavals of the 1960s. The concept of “a risky mix” applied not only to the environmental threats of intermixing the fauna and planktonic flora of two oceans.85 It also involved the professional hazards facing scientists who stepped too far outside their idealized realm of social isolation.

Biological Disaster or Grand Evolutionary Experiment?

Rubinoff’s 1968 article opened the floodgates of critique from fellow biologists. The major intellectual disputes encompassed conflicting interpretations of the limited empirical research on transisthmian evolution, biological diversity, and biotic mixing, and of the validity of the Suez and Panama Canals as models for predicting how the sea-level waterway might affect ecological and evolutionary processes. Some participants also questioned Rubinoff’s more explicitly political assumptions and framing choices. At a time when the negative environmental consequences of modern technoscience were gaining more and more attention, but when marine biodiversity and bioinvasions barely registered as issues of concern, the debates reveal how biologists of different disciplinary backgrounds and levels of conservationist concern struggled to communicate the political relevance and fund-worthiness of a topic for which they lacked a common vocabulary and conceptual understanding.

The first published scientific response to Rubinoff’s essay came from the ichthyologist and marine zoogeographer John C. Briggs.86 While appreciating the redirection of scientific attention away from radiation damage, Briggs took issue with Rubinoff’s sense of opportunism and inevitability. The breaching of the isthmian zoogeographic barrier would, he predicted, allow animals of the apparently more species-rich western Atlantic ecosystem to dominate their relatives in the eastern Pacific, eventually wreaking havoc on the latter: “Let us not be concerned about preparation for a great biological experiment. The important question is: Should the sea-level canal project be undertaken at all? Are we prepared to assume the responsibility for the irrevocable destruction of several thousand unique species in the Eastern Pacific?” For Briggs, the sea-level canal proposal posed “a conservation problem of an entirely new order of magnitude.”87

The absurdity of conducting routine baseline research in the face of an extinction crisis led Briggs to publish a much longer article in the January 1969 issue of BioScience with the striking subtitle “Potential Biological Catastrophe.” He argued that the Suez offered disturbing empirical evidence of how organisms from a richer marine ecosystem might outcompete the natives of a less stable one, as shown by the aggressive migration of Red Sea fishes, crustaceans, mollusks, and tunicates into the empty niches of the nutrient-poor eastern Mediterranean. Briggs calculated that 6,720 Caribbean species would migrate westward through a Central America sea-level canal and 4,480 less robust Pacific species would move eastward, resulting in massive extinctions among the latter. While suggesting that a sea-level waterway could be designed to kill migrating animals with chemicals or hot water, Briggs deemed such methods “risky and distasteful” and instead called for improving the existing canal to meet the needs of world shipping.88

Briggs’s analysis provoked strong reactions from fellow members of the scientific community. Rubinoff and other scientists questioned his statistical methods and assumptions.89 Biological oceanographer Gilbert Voss later implicitly called Briggs and Mayr “two of the most outspoken alarmists [who] have had no personal experience in the areas and have not engaged in research relating to the problem.”90 And the eminent ichthyologist Carl Hubbs, whose research on the native and nonnative fishes of both the Great Lakes and Suez Canal dated to the 1920s, probably had Briggs in mind when he urged the president of the National Academy of Sciences in February 1969 to appoint a committee to address the questions raised by the sea-level canal. In contrast to “the irresponsible nature of some of the published discussions,” Hubbs emphasized, “I am deeply impressed with the potential biological consequences, for better or for worse, and with the fantastic opportunities for research that are presented,” points he reiterated at oceanographic and zoological meetings in Curaçao and Caracas.91 Hubbs’s points underscored the failure of biological oceanography and marine biology to keep pace with the advances in physical oceanography made possible by Cold War military patronage of the earth sciences.92

Hubbs also drew on emerging research by the Smithsonian-Israeli collaboration to support his assessment of the Suez as “an imperfect model” for estimating the biotic effects of the proposed Central American canal.93 The two isthmuses differed in terms of not only salinity levels but also geological histories. The more recently separated coastal Caribbean and Pacific biotas contained many closely related pairs of species, whereas the Mediterranean and Red Sea biotas contained almost no such sister species, differences which presented “extremely urgent, and at the same time very promising” opportunities for systematic, ecological, and evolutionary studies.94

A stark rejection of the Suez situation as a valid precedent came from a STRI predoctoral visitor, Robert Topp. It was no surprise, he argued, that Red Sea ichthyofauna had occupied the vacant niches of the impoverished Mediterranean. By contrast, because most of the ecological niches on either side of the Central American isthmus were already filled, species introgression through a sea-level canal would likely not cause widespread extinction. “Faunal enrichment” might even occur, especially in the Caribbean.95

In support of his prediction that the proposed waterway would not cause widespread extinctions, Topp mobilized new evidence made possible by other visiting researchers to Panama and the Smithsonian’s internal funding. After towing cheesecloth-wrapped marine animals through the canal, Robert Menzies concluded that genetic exchange was probably already occurring on a large scale due to the ability of fouling organisms attached to the bottoms of ships to survive the full fifty-mile transit.96 Another visiting biologist studying marine plankton transport, Richard Chesher, confirmed via interviews with Panama Canal Company officials that tankers and freighters had been required since 1956 to ballast down prior to the transit to ensure maneuverability.97 “Much biotic transfer” was thus probably already occurring as ships made the eight-hour journey and then emptied their ballast tanks on the other side, to no ill effect.98

Topp’s paper provided vindication for Sheffey, who was upset by a CBS television report on the proposed canal that, in his view, minimized the fouling and ballasting means of marine species transport that had been occurring since the Panama Canal’s opening in 1914.99 But Rubinoff countered that such modes of dispersal rarely contained enough individuals of any given species to allow colonization. He also questioned the scanty empirical evidence for ballast-mediated carriage, arguing that Menzies used intertidal organisms preadapted to survival in fresh water and that Chesher overlooked the toxic anticorrosion coatings lining ballast tanks. He did concede that modern tankers with stainless steel tanks—most of which were too large to use the existing canal—might enable plankton to survive passage from ocean to ocean. “The actual role of ballast transport through the present Canal is a subject that could be properly evaluated, and a thorough study should remove this area from speculation,” he argued, as did other sea-level canal authors.100

Of course, such research could be conducted only if funding came through, and to that end, the CSC and Smithsonian brokered a strategy to try to resolve the problem that had occupied Smithsonian naturalists for the past half decade. The commission scrounged up enough funds to elicit the National Academy of Sciences to lend its authority to the quest for external federal support of a comprehensive tropical marine biological inventory.

Conclusion

The CSC conveyed its fifth annual report to the new president, Richard M. Nixon, in the summer of 1969. The report acknowledged the Route 17 clay shale problem, as well as the expanded efforts to address marine biotic exchange. However, like his predecessor Nixon neglected these points in his public message when he forwarded the report to Congress, focusing instead on the good news: the engineering feasibility team had completed data collection efforts and closed down all field operations; the diplomatic, economic, and military subgroups were wrapping up their evaluations; and the Plowshare scientists had conducted the third 1968 cratering experiment, Project Schooner, at the Nevada Test Site. While conceding that all six planned shots would not be completed prior to the December 1970 deadline, the commission still expected to render its conclusion by then on the feasibility of nuclear explosives for canal excavation.101

Neither the CSC report nor the president, however, mentioned another setback, the uncontrolled release of radioactivity by the 35-kiloton Schooner explosion. Five days after creating a crater of 725 feet wide and 250 feet deep on December 8, 1968, the experiment caused radiation levels at sampling stations as far away as Ontario and Quebec, Canada, to rise to ten to twenty times above normal background levels.102 The fifth annual report also glossed over Panama’s revolutionary events of October 1968—the military coup staged by Omar Torrijos and other officers of the Guardia Nacional. Soon after taking control of the government, Torrijos established his own Office of Interoceanic Canal Studies and ordered an investigation into a Panamanian-built seaway using nonnuclear methods along the Route 10 site west of the existing canal. While hinting at the recent political changes, the international relations section of the CSC document praised the U.S., Panamanian, and Colombian officials whose cooperation made the field surveys possible. “A large quantity of environmental information has been acquired in areas of the isthmus that previously had been little explored,” valuable data that would soon be made public.103

Yet from a high-modernist standpoint, new scientific knowledge of the mythic Darién landscape failed to counterbalance the increasingly bad news about PNEs. Reported a Panama American journalist in the spring of 1969, “an atomic engineers’ dream . . . is fading into a ditch diggers’ pick and shovel nightmare.”104 That history could move backward, from the space age to the olden days, seemed incredible to the friends of Plowshare. So did the insistence of biologists that the canal engineering feasibility studies address issues that had nothing to do with radioactivity, just so they could resuscitate the old-fashioned study of natural history.

Today, fifty years on, it is clear that those demanding realistic, comprehensive assessments of the megaproject’s environmental effects were as forward-thinking as the other sea-level canal stakeholders. The Plowshare physicists and allied engineers sought to advance the unproven field of nuclear excavation, and U.S. officials aimed to update the isthmian transportation system and relations with Panama. Likewise, the marine evolutionary and ichthyological scientists sought to revitalize relevant naturalist disciplines to analyze the enormous ecological changes a wide channel at the level of the seas would induce. The sea-level canal proposal served as a modernization strategy for a wide range of stakeholders, and it facilitated many kinds of work with far-reaching political and intellectual effects.