Should history be the guide to biodiversity?

When I started visiting Point Reyes National Seashore in the 1960s, it was a treat to see one of the fallow deer the park had inherited from its ranching past. The Middle Eastern species, introduced for hunting half a century ago, has several color phases from white to blackish brown, and the stags have impressive antlers. Today, it’s less of a treat because it’s hard not to see fallow deer. Their population has grown to almost 900, and some meadows look like feedlots.

Earlier this year, the Park Service announced a plan to remove fallow deer from the Seashore, along with another exotic species, the Asian axis deer, which numbers almost 300. Officials say the axis deer population could double within six years and that both species are competing with native blacktailed deer, damaging adjacent farms and threatening to spread elsewhere.

Given those reasons, I think the exotic deer should be removed. But I’m glad it’s not my job. A few years ago the Park Service had to stop a deer-culling program because of public displeasure, and its new proposal won’t be popular. People like to have diverse fauna in parks.

But perhaps there is a lesson in this unhappy affair: We need to think more about the meaning of biodiversity in our parks.

When the Point Reyes National Seashore was established in 1962, biologists must have foreseen that three species of medium-size deer in the same habitat would cause problems. They probably should have removed the smaller populations at that time.

But unfortunately we don’t allow the Park Service to think ahead much because we underfund them and thereby keep them busy dealing with crises that arise from lack of foresight -- like the present exotic deer explosion.

If we were to let the Park Service plan ahead, on the other hand, the results could diversify park fauna in a more positive way. Take the free-roaming native tule elk at Point Reyes. As an experiment, the Seashore maintained a fenced herd at Tomales Point beginning in the 1970s. Some elk of that herd were released in the Seashore’s Phil Burton Wilderness Area in the 1990s. The elk don’t harm blacktails, and they are more interesting to watch than fallow or axis deer.

Still, the proposed removal of two thriving and attractive species from the park raises a knotty planning question. Are blacktailed deer and tule elk the only native ungulates we can have in Point Reyes, and, by extension, in much of California?

This relates to a debate that has been raging for decades about the definition of “native.” In the 1960s, a national panel of experts, the Leopold Committee, advised the Park Service to set a goal of maintaining (or re-establishing) the species that had lived in parks at the time Europeans reached the Americas.

But scientists such as Paul S. Martin, a paleontologist at the University of Arizona, believe that this is too limited. For if we are really interested in biodiversity, we should go further back in time. The fossil record shows that North America once had almost as many mammal species as Africa, but human hunting, albeit prehistoric human hunting, extirpated much of the native megafauna.

The debate is already on the ground at Point Reyes. We know that pronghorns inhabited the Bay Area in historic times, but it is unclear whether they lived at Point Reyes, and there are no plans to reintroduce them there.

Still, pronghorns almost certainly lived at Point Reyes at one time because they’ve been in North America millions of years.

I don’t know if pronghorns could do well at Point Reyes. I do think Martin has a point when he says that confining park biodiversity to historic levels may be unnecessarily austere. Point Reyes, for example, might accommodate at least one more reintroduced, large ungulate besides elk and pronghorns.

There are areas of the Seashore where exotic deer remain scarce -- the deep forest in most of the wilderness area. Even blacktails aren’t common there. Indeed, large ungulates are scarce in most West Coast forests now. Has this always been so? Not according to the fossil record, which shows that California forests contained not only extinct giants such as mastodons and ground sloths, but also the tapir, a surviving relative of horses and rhinos that can weigh 500 pounds.

Tapirs live in South and Central American forests today, but fossils show they inhabited North America from 50 million years ago until 10,000 years ago. You can’t get much more native than that. According to Martin, North American tapirs disappeared not because of climate change, as was once generally believed, but because prehistoric hunters extirpated them. If so, tapirs could live here again.

The local Sierra Club chairman told the San Francisco Chronicle that we should remove exotic deer from Point Reyes because we imported them (neither species inhabited North America before). Maybe we should return tapirs there because, albeit long ago, we removed them.

I don’t know if tapirs could thrive at Point Reyes, but there are parts of the wilderness area that look like tapir heaven, such as the Crystal Lakes, a primeval expanse of marsh, ponds and conifers. I don’t think they would conflict with farms and other ungulates. Tapirs are shy and solitary.

Hunting and deforestation are threatening tapirs all over South and Central America, so it might be good long-range planning to reintroduce them. There might be other benefits. Having large herbivores back in the forest could reduce potential wildfire intensity and increase plant diversity.

Along with the elk and blacktails in the park’s meadows and coastal scrub, visitors would have a rare chance to see a living fossil among its Douglas firs, maples and oaks.

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David Rains Wallace is the author of “The Klamath Knot: Explorations of Myth and Evolution” and “Beasts of Eden: Walking Whales, Dawn Horses, and Other Enigmas of Mammal Evolution.”