Now Nimoy had the general idea: some form of life that human unconsciousness causes to disappear in the 20th century is suddenly crucial to human life in the 23rd century. At first he considered plants. There are millions of species that humans haven't even catalogued, and many of these will be forced into extinction before we know they exist. Among them could very well be plants that can serve as sources for pharmaceuticals that treat or cure currently intractable diseases and conditions. What if 23rd century earth were stricken with a plague, and the only cure comes from a flower that no longer exists?

But traveling three centuries through time and overcoming other obstacles to rescue a medicinal plant would be hard to dramatize and visualize effectively---the proportions seemed skewed. Besides, the idea of thousands of people suffering and dying from a plague didn't suggest a light-hearted movie.

Then Nimoy's conversation with a friend about endangered whales inspired the basic solution. Whales had the dramatic proportions, and a long, complex relationship with the human species. Celebrated as "King of the boundless sea" (from one of some eighty quotations Herman Melville recorded at the beginning of Moby Dick), they were now becoming known as mammals with formidable intelligence who seemed to communicate.

The eerie songs of the Humpback whales caught the public imagination when they were first recorded in the 1960s, though experts could not agree on what the songs signified or even how they were sung (these whales have no vocal chords.) The songs were complex, and seemed to change over time and be communicated---even learned--- over distance, all of which deepened the mystery of these beings.

And though humans weren't fully conscious of the consequences of eradicating them, deliberate and aggressive action was responsible for taking them to the brink. Over more than a century, humans hunted whales to the extent that several species, including the humpbacks, were nearly extinct. (Even though killing them has now been illegal for decades, there are still only a few thousand blue whales and some 30,000 humpback whales in the world.)

In the early stages of its development William Shatner was not yet officially on board for Star Trek IV because he was negotiating with Paramount. But he was being consulted and kept informed. He wasn't in favor of the time travel device, but he loved the whales. Several years before, Shatner had toured a one-man show in which he used recorded whale song juxtaposed with his live reading of D. H. Lawrence's "Whales Weep Not" (which as Captain Kirk he would eventually quote in Star Trek IV.)

Shatner did this show in conjunction with Greenpeace, the activist organization based in Canada. Its name symbolizes its two principal activities: the "green" denotes its efforts on behalf of endangered species, particularly whales; the "peace" signaled the activism with which it started, opposing nuclear bomb testing, which also is an environmental issue.

The organization's first campaign was to stop an underground nuclear test on Amchitka island in Alaska in 1971. One test had been accomplished, even though it took some skullduggery by President Richard Nixon to keep the U.S. Supreme Court from preventing it. Greenpeace chartered a boat and headed for the site of the second test in its heavily publicized attempt to stop it. Though the boat was intercepted and prevented from returning, protests had erupted across Canada, and the U.S. postponed and eventually canceled this test.

With that one act, Greenpeace may have done more for the environment than it knew. The first Amchitka blast not only killed thousands of animals and birds, it ruptured the earth's crust, sending radioactive elements into the fresh water supply for Aleuts living nearby. Cancers there increased markedly, and even in 1996, radioactive tritium and cesium-137 were still leaking into the Bering Sea. A second bomb explosion in the same area might have been led to even greater catastrophe.

Greenpeace became so active in disrupting French nuclear tests that their boat was rammed, then boarded and the people aboard beaten, and finally a team of French operatives actually blew up their boat, killing a photographer. But the French tests eventually stopped.

In the early 70s, Greenpeace inaugurated the very visible "Save the Whales" campaign. Then they decided to put activism where their images were. In 1974 a Greenpeace boat confronted Soviet whalers off the California coast for the first time. On Zodiac inflatables, volunteers placed themselves between the whaling ship's harpoons and the target whales.

It was this act, repeated throughout the 1970s and into the 80s (targeting Icelandic and other whaling fleets as well) that Leonard Nimoy says was the specific inspiration for one of Star Trek IV's best remembered scenes: the whaling trawler's harpoon bouncing off the Klingon Bird of Prey, hovering above to protect the whales. It was also this activism that inspired William Shatner to engage his skills and celebrity for the Greenpeace efforts to save the whales.