Michael L. Rosenzweig
Dept. of Ecology & Evolutionary Biology
University of Arizona
Rosenzweig, M. L. 2006. Beyond set-asides. Chapter 21 in The Endangered Species Act at Thirty. (eds. D. D. Goble, J. M. Scott and F. W. Davis). Washington, DC, Island Press. pp. 259-273.
Almost by definition, endangered species have small, even tiny, geographical ranges. So, in practice, the Endangered Species Act often translates into a set-aside strategy: “This reserve exists to protect the Chiricahua leopard frog. Look perhaps, but don't touch!”
Can a set-aside strategy work? Endangered species are alive and dynamic, not static museum displays in carefully sealed chambers. They must live in nature, not in a glass case. Can a strategy that relies on hermetically sealing them off work for long in the face of nature’s dynamism?
I suspect that human nature, all by itself, will prevent set-asides from doing their job for very long. The very word ‘set-asides’ suggests the problem: We have not forgotten about them, it is just that, for now, we can don’t need to use them for ourselves. It is not hard to see what will happen when we do. Set-asides are foredoomed to last only so long as people do not perceive a need for them. Surely this matter is crucial. However, I’ll leave it to those who understand human nature better than I do. I’ll take refuge in science.
Can a set-aside strategy work? Science gives us a clear, unqualified answer. Unfortunately it is “no.” Set-asides can slow our loss of species but cannot stop it and cannot much affect how many species we lose in the long run.
With excellent justification, conservationists agree that loss of habitat is diversity’s worst problem. That loss creates both of the principal reasons for the “no.” One is well known, the other less so but just as important. The first is global warming (and other pervasive anthropogenic alterations of the world’s air and water). The second has to do with issues of extent -- area. It turns out that size really matters a lot!
The impact of global warming
Fundamentally, species have habitat needs and those needs have changed very little in the past few centuries. For most species, those needs do not include a football field, let alone the grounds of a steel foundry. As a matter of fact, they do not even include most city parks or gardens or ‘modern’ farms or tree plantations.
German has a good word, ‘kulturmeider’, to describe species that cannot use anthropogenic habitats. To fulfill their habitat needs, kulturmeider depend on the environmental relics of millennia-past. Set-asides are nothing other than those environmental relics.
The places where these relics hang on have become especially small and fragmented in the past century. However, as we change the climate of the globe, those relictual habitats change, too. A degree or two of global warming and, behold, what was a habitat that could support its residents becomes one they can no longer use (Peters and Darling 1985). In times past (say when glaciers were retreating at the end of the last ice age), many species just drifted poleward or upslope (Coope 1987; Davis 1983). Today, that tactic may take them into a Walmart parking lot, where they will die because they cannot digest asphalt. The point is simple, but deserves two brief illustrations.
One comes from South Africa, whose heathy fynbos ecosystems gave birth to nearly 9,000 species of plants (Cowling et al 1989; Cowling and Richardson 1995). A few of these have been domesticated (such as Pelargonium) and grace our homes. But most are at the mercy of man’s need for land. Several set-asides contain much of this plant diversity. One of the most important is the national park at the Cape of Good Hope. Many of its plant species grow only in the park or nearby, quite likely because the climate is not appropriate much farther north. With a degree or two of global warming, their climate will have been driven into the Southern Ocean. To survive, they must learn how to take root in sea water.
A second example, also from the southern hemisphere, comes from the limited highland habitats of tropical Queensland (Williams et al 2003). Sixty-five species of montane rainforest vertebrates are endemic to these highlands. There are herbivorous possums (Strahan 1983) and a number of species of tiny frogs and birds and lizards. Most of these species inhabit a restricted band of elevations - a mountain in tropical Queensland’s far north is a layer cake of diversity. What will happen to the species in the top-layer when global warming sends the temperatures of their habitats up into the heavens? Will the frogs grow wings? Highland habitats around the world, especially tropical ones, often contain endemics. These Queensland natives represent the peril to them all.
Loss of area
Even without global climate change, set-asides are too small to help for very long. Set-asides try to preserve ecosystems but area turns out to be one of the intrinsic properties of ecosystems, especially with respect to the generation and maintenance of diversity. So a preserved, shrunken ecosystem is a contradiction in terms. A preserved, shrunken ecosystem works little better than a preserved, shrunken head. I shall explain.
Science has been aware for two centuries that more area supports more species. During that time, many have participated in gathering data to quantify the relationship of species diversity to area. Many others have worked on analyzing them and modeling them (Rosenzweig 1995; Rosenzweig and Sandlin 1997).
There are several species-area relationships (Rosenzweig 1999a; Rosenzweig 1999b). Which one governs a set of places depends on the timescale of the most important process that contributes species to a place.
If different areas each have their own endemic species, then those areas are known as biogeographical provinces. (Note: one or more may be geographical islands, e.g., the state of Hawaii is a biogeographical province for its birds and plants.) Evolutionary processes (speciation) rule, and the species-area relationship among different provinces has a slope near unity (in logarithmic coordinates). This means that for each increment of area, diversity grows linearly (Rosenzweig 2001).
If different areas share a pool of species produced by the same set of evolutionary events, and all species can almost always replace their populations generation-by-generation, then those areas are biogeographical islands. (Note: they may not be geographical islands, e.g., a set of mountaintops is often a biological archipelago; Vuilleumier 1970). Immigration processes rule because they happen faster than speciation. The species-area relationship among islands is characterized by a law of diminishing returns: with each successive increment of area, diversity grows less and less. In logarithmic coordinates, the slope of a species-area relationship among islands is generally close to 0.25 (MacArthur and Wilson 1963; Preston 1960).
In some cases, different areas share a pool of species produced by the same set of evolutionary events, but some populations in each place cannot manage to reload on their own. To persist, they depend on generation-by-generation dispersal from more fortunate populations. Dispersal processes rule because they happen so much faster than the others. A set of such places also exhibits a law of diminishing returns. But it is even more pronounced than that of islands: As area increases, diversity grows very quickly at first, but practically levels off once a rather modest amount of area is censused. In logarithmic coordinates, the slope of a species-area relationship among such places is generally close to 0.15 (MacArthur and Wilson 1967).
Applying species-area relationships: scale matters
The first application of species-area thinking to the conservation of species came from island biogeography (Wilson and Willis 1975). Set-asides were viewed as islands in a sea of artificial, sterile habitats. The theory was used to ask questions about how money should be allocated for optimal design of reserves. The most famous: SLOSS, single large or several small?
A century ago perhaps, one could justify approaching set-asides as islands. A great deal of relictual or quasi-relictual habitat still spread across the face of the land. But that is no longer true. Today’s set-asides are not islands because they are usually all that remains for so much of life’s diversity. Islands, remember, get most of their species as immigrants from a mainland source-pool. If our set-asides were to lose a species, they would have no source-pool from which to replenish their stock. No, in most cases, if today’s system of set-asides were to lose a species, it would be gone forever. Species can get added to a place, but only by speciation. That means today’s system of set-asides is more like a set of provinces than anything else.
But that is a crucial distinction. Because of the strong law of diminishing returns that characterizes the species-area relationships of archipelagos, islands do not have to be very large to contain a high percentage of a source-pool’s species. For example, a single island with only 1% of the area of a source-pool can rather reliably harbor about 32% of its species. Given the power of small islands, one can easily imagine that a set of island reserves could conserve most of the species of the pool. However, this is not at all the case if reserves are actually provinces (Rosenzweig 2003b). A province reduced to 1% of its former area can maintain only 1% of the old diversity; one reduced to 5%, can maintain only 5% of the old diversity, etc. With provinces, you get what you pay for; there are no bargains.
Because people wisely and carefully target what they set aside by focusing on assembling a wide variety of scarce species and scarce habitats in set-asides, they are managing to slow extinction rates (Rosenzweig 2003c). Targeting species in obvious trouble has helped a few of them (e.g. Denton et al 1997). Targeting the ecosystems that have suffered the most has helped some of the threatened and endangered species that live in them (National Research Council 1995). But these gains will be temporary unless we find ways to expand the habitats that species can use. Eventually nature will establish a new, much lower diversity in our reserve system, a diversity that reflects its proportion of the continent. And global climate change will hurry the approach to this new and depauperate state.
Guarding species from extinction requires thinking outside the set-aside box. People are doing that all over the world. They are reconciling human and nonhuman use of habitats by inventing, establishing and maintaining new habitats where people live and work and play (Rosenzweig 2003c). The goal? To conserve species diversity by allowing wild species to use our spaces. I call this kind of science ‘reconciliation ecology.’
Efforts to save longleaf pine forests involve two good examples of reconciliation ecology, one directly related to the ESA. Growing only in the southeastern USA, longleaf pine forests support dozens of plant and animal species. Three hundred years ago, they covered some 36-million hectares. By 1990, only 2,000 hectares remained - and they were disappearing fast. Enter four well-known organizations: The Nature Conservancy, the US Dept. of Defense, Environmental Defense and the US Fish and Wildlife Service.
ED and USFWS were wrestling with the problem that many rare and endangered species have populations on private property and private landowners feel threatened by the ESA (Wilcove et al 1996). They see it depriving them of their property rights. Many landowners will not even allow survey work to be done on their land for fear that the government will find ‘one of those species’ on it, and shut down their use of their own land. A perverse way to avoid that ever happening is to destroy good habitat that might support a rare species, and this has apparently taken place.
So ED and USFWS cooperated to produce Safe Harbor, a purely voluntary set of programs keyed to the ESA. Each program is conducted in the name of one or more endangered species. Safe Harbor began in the sandhills of North Carolina in 1995, where the hook is the red-cockaded woodpecker (Picoides borealis) - listed since 1973 when the ESA was born. Red-cockaded woodpeckers virtually depend on longleaf pine trees for their nesting sites.
Land to be enrolled in Safe Harbor might already have had some of the woodpeckers and been restricted by the ESA; these baseline restrictions continue. Each landowner agrees somehow to improve the enrolled land for the woodpeckers over a fixed period of years. Perhaps one owner will undertake controlled burns to rid the understory of oak species that can choke out longleaf pine seedlings. Perhaps another will agree to drill holes in the pines for woodpecker nests. (The woodpeckers take years to do one; drilling crews take an hour.)
In return for improving the habitat, only the baseline restrictions apply. Should the improved habitat attract any new woodpeckers or other threatened species, Safe Harbor shields the landowner from any further ESA restrictions. This shield lasts during the term of the agreement. At its conclusion, the landowner is free to withdraw the land or renew the agreement.
By the spring of 2003, 169 landowners in six states had enrolled almost 200,000 hectares on behalf of red-cockaded woodpeckers - much of it longleaf pine. The pine forest is coming back. And the woodpeckers are breeding in places long abandoned. These and a growing number of other Safe Harbor programs in a total of fourteen states are now protecting a diverse set of habitats in the names of various species of threatened or endangered birds, mammals, frogs, mussels and fishes (Environmental Defense 2004).
The Nature Conservancy, which cooperates with USFWS by administering Virginia’s Safe Harbor program, is actually the veteran private organization when it comes to producing reconciled longleaf forest. In 1990, The Nature Conservancy and the US Dept. of Defense began work on Eglin Air Force Base near Pensacola. Over the years, they have chopped and planted, burned and drilled until they created a new longleaf forest of nearly 100,000 hectares. They have not restored the original longleaf ecosystem. Nothing can do that. But they did fashion and do manage a new one, fully used by the military and by campers, loggers, fishermen and hunters. You may recall that just before the Iraq War started, the US demonstrated MOAB - the 21,000-pound Mother-Of-All-Bombs - by dropping one on a bombing range in Florida. Eglin Air Force Base was that range; it is no nature reserve.
Meanwhile, the pocket parks of Mayor Richard Daley’s Chicago convert abandoned gas stations into islands of nature for inner city residents (Shore and Packard 2000). Prairie Dunes Country Club’s golf course in Hutchinson, Kansas hosts some 35,000 rounds of golf a year, but also manages its roughs to support a large number of wild species (Terman 1997). Florida Power and Light’s Turkey Point nuclear- and coal-powered electricity generating station near Miami has 80 miles of cooling canals, canals that it has made into crucial managed habitat for the rare American crocodile and many other species (Gaby et al 1985). And 30,000+ homeowners cooperate with the National Wildlife Federation to build and manage a Backyard Habitat™ on their own property (National Wildlife Federation 2004; Tufts and Loewer 1995). There are many, many more examples (Rosenzweig 2003a). Reconciliation ecology is already freeing a lot of wild species from their set-aside ghettos. It works.
Reconciliation Ecology and the Endangered Species Act
Reconciliation ecology can help the Endangered Species Act do its job effectively. By the same token, reconciliation ecology won’t be effective without the ESA or something very like it. These interrelationships involve:
changing the way people think about saving species
expanding species ranges
helping to stimulate more research about species’ habitat requirements
relieving some of the pressure on set-asides
I will now explain each of these points.
Reconciliation ecology and conservation attitudes
Reconciliation ecology impinges on the attitudes that pervade conservation. It does this first by heeding the significant new science which shows that set-asides cannot work for long. Reconciliation ecology admits that area is an intrinsic property of ecosystems, and that global climate change menaces the set-aside strategy even in the fairly near future. Thus, reconciliation ecology, although it is applied ecology, uses basic ecology to the hilt and encourages all branches of conservation ecology to follow suit.
It also contributes to environmental peace. It actually encourages continued use of the land by people and their enterprises. Its strategy involves using land better instead of setting land aside. (But it also supports the limited use of other strategies that do set land aside.) It is not ascetic or Luddite. It does not advocate depriving human beings of comfort or profit; rather it seeks to find ways to allow those profits to continue and those comforts to increase. These attitudes, it seems to me, ought to foster a milieu of detente -- perhaps even cooperation -- between ecological and economic interests. How much time, energy and money do we now spend battling each other over issues of endangered species? How much more effective could we become if we could reduce the inefficiencies of our friction?
To be effective, efforts to conserve diversity such as the ESA require a good deal of popular support. Reconciliation ecology will increase that support dramatically, not by preaching but by surrounding people with diversity.
Pauly (1995) points out that people evaluate their environment in relationship to what they have known. If something seems familiar, they tend to endorse it. If, on the other hand, it seems a deterioration of their previous environment, they tend to oppose it. Because each generation experiences a new set of environments, each starts with a new baseline of expectations. Pauly calls this set of realities the “shifting baseline syndrome.”
Since diversity has declined in man-made habitats, so has the baseline of human expectations. People are happy seeing fewer species and find it impossible to imagine a world teeming with diversity -- as impossible as meeting a living dinosaur. In such a world, the goals of the ESA become hard to take seriously. People wonder what diversity might be good for. If they were to experience diversity as a commonplace the way their forebears did, they would not wonder. They would wonder at it!
Enter reconciliation ecology. Because it raises diversities in places used intensively by people, it raises the shifting baseline. That should redound to the benefit of all efforts to conserve species diversity, including those of the ESA.
The reciprocal effects seem clear and straightforward. Among other things, ESA is the formal recognition that many species need our help. It is society’s call-to-arms. Reconciliation is one response; it would have no meaning without the call.
For now, ESA also provides a bulwark that allows one to imagine reconciliation ecology. By delaying the tide of so many extinctions, it gives a face to the species we might try to welcome in our habitats. It also helps us to take heart, to believe that we have some time and can do some good. In my view, that hope is not misleading.
Expanding species ranges
Reconciliation ecology results in the expansion of species ranges into newly designed habitats. Most often those habitats will be unprotected private property. What if one of those species is endangered or threatened? Will the ESA and reconciliation ecology conflict?
The overriding concern here is saving species. So reconciliation ecology must ensure that the two do not conflict. Perhaps this will not be difficult: All conservationists worry about species with small geographical ranges. A species newly limited to a very small geographical range is an ominous sign indeed. If reconciliation can reverse that, if it can expand species ranges, it may allow us to remove some threatened species from the red list.
But there are devils in the details. Reconciliation ecology may advocate the establishment of populations away from the protective wing of reserve managers. It may wish to break down the genetic differences between demes in a metapopulation-- not merely for the sake of doing so, but because establishing a new deme may require translocations of a few individuals each from several old demes. Will conservation allow the removal of individuals from established populations of threatened and endangered species to locations where they may once have lived? Under the ESA such translocations can be difficult.
Some of the Safe Harbor agreements tacitly admit such problems by solving them. By summer 2002, the Georgia Department of Natural Resources, administering their Safe Harbor agreement, had already moved seven groups of red-cockaded woodpeckers to sites enrolled in Safe Harbor. If Safe Harbor, which is an extension of the ESA, can allow translocation of such a charismatic endangered species, reconciliation projects should face nothing but a bit of extra paperwork from the problem.
In Arizona, we are seeing similar good sense applied to fish that are both listed and potentially good at mosquito control (MacMullin 2004). Two topminnows and two pupfish were granted safe harbor status in April 2004. That means they can now be spread (within their natural range) to waters - even to artificial bodies of water - where they do not now live.
And then there is the genetic purity issue. Biodiversity includes the concept of genetic diversity. We diversity nuts are in favor. More than that, the ESA takes diversity to the subspecific level wherever it can. And we are in favor of that for sure. Further, we who are evolutionary biologists recognize the strong possibility of local genetic differentiation among the demes of a species. It is a well- and often-documented phenomenon. Won’t expansions of endangered species into new habitats blur or erase such differentiation?
By definition, the ‘original’ subspecies, clone or race of every species inhabiting a new habitat is ‘none.’ But those that move in cannot expect to avoid genetic change. New habitats always bring new adaptive challenges.
Suppose then that we succeed in designing and deploying a new habitat for (say) Heerman’s kangaroo rat. All of a sudden, these guys are hopping around in Santa Monica backyards. And all sorts of other now improbable spots. If we can satisfy their habitat needs, most individuals of the species will live with us. And that will force them to change, perhaps rather quickly (Ashley et al 2003). California will retain a species of Dipodomys, but it may not look or act quite the same as it does today. Will we have saved Heerman’s kangaroo rat? Or hastened its extirpation?
What a philosophical gold mine! Nevertheless, I hope those who care about diversity refuse to exploit it. Pointless scholarly debates, obfuscating learned symposia, and the large grants that may be awarded to support such activities do little but siphon money and public respect away from practical conservation. How many genes will fit on the head of a pin?
Reconciliation ecology ignores the question. It admits that life evolves and genomes change naturally. And it seeks to supply an immense theater in which such change can happen. After all, the alternative is the prospect of total loss. I know the ESA does not prefer total loss. But does the ESA insist that if it cannot save a species in its current genetic state, it has to ignore it? If that is its position today, we must not let it remain so.
Stimulation of habitat research
Proponents of both the Endangered Species Act and reconciliation ecology share a profound interest in understanding the habitat requirements of the species they wish to protect. But they share only the goal. Getting to it could involve them in some serious disagreements about methods and interpretations.
Consider the fact that the usual strategy to determine the habitat requirements of a species is to combine spatio-temporal censuses of a species with measurements of the habitat variables likely to affect it. For instance, suppose a grassland species reaches peak populations in places with annual summer precipitation of 150 millimeters (38 inches) and is not seen in areas with annual summer precipitations below 75 millimeters (and 19 inches) or above 200 millimeters (51 inches). From those facts one would then hypothesize that the species requires both grassland and such levels of rainfall.
Actually, most of us do not hypothesize; we conclude. And therein lies the rub. The habitats used by a species in nature may not accurately reflect that species’ real needs or preferences (Rosenzweig 1981). How can that statement be true?
In the simplest case, a species may not have the opportunity to live in a better place simply because such a place may not actually exist in nature. For example, the city of Tucson, Arizona, teems with several desert bird species living at population densities more than twice those found anywhere in nature. And this fact has created previously unknown high densities of food for some previously scarce raptors, especially Cooper’s hawk (Accipiter cooperii). Cooper’s hawk has responded with high densities of its own (Boal and Mannan 1999; Mannan and Boal 2000). I have seen the latter hunting mourning doves 3 meters (10 feet) above the tarmac of a city gas station! Nothing I ever saw in Arizona’s canyons, where Cooper’s hawk is a scarce native, prepared me for that sight. Some species will astonish us with their ability to exploit the new habitats we create.
A more complex case stems from population interactions among species. For instance, competition may force a species that can tolerate a wide variety of habitats to live solely in marginal habitats (Rosenzweig 1991). Meanwhile, its competitors cannot tolerate the marginal habitats and must have the best ones in which to live and reproduce. We often misinterpret such a competitive relationship. We observe the intolerant species in one type of habitat and the tolerant species in another. Then we erroneously conclude that each species is living in its best habitat.
It takes field experiments to ferret out the truth of tolerance-intolerance competition. Experiments may involve manipulating population sizes in field enclosures (e.g. Abramsky et al 1990), temporarily removing individuals from nature (e.g. Pimm et al 1985). They may involve manipulating the habitat, too (e.g. Rosenzweig 1973).
Manipulative experiments make the guardians of endangered species and the managers of set-asides bristle with disapproval. During our 20-year study in a sand dune reserve in Israel, Zvika Abramsky and I experienced this attitude first hand. Despite our being their allies in species preservation, we faced their repeated interference with our experimental plans. “Look, don’t touch,” they often insisted. We attribute this interference to misguided devotion to duty on the part of the reserve managers, but interference it was
A similar dispute involved experiments planned to discover the habitat requirements of spotted owls in northern California. After years of cooperative planning involving the Forest Service, a commercial timber company, community representatives and an academic (me), we called a public meeting to announce a plan whose goal was sustainability for both the forest and the owls. Our plans did not involve any set-asides at all and the owl was not listed as threatened or endangered. Yet, the very next day, the plan was challenged in court and stopped!
Species enter modern times with a lot of evolutionary history behind them. Natural selection has molded them to succeed with a certain body having certain behaviors in certain habitats. They cannot adapt instantly to the new demands we place on them. Reconciliation ecology calls for natural history research so that we can learn the limits of their current state. What do they need? What do they have that they can do without? We’re not likely to succeed if society will not encourage us to conduct our research in the natural areas that best reflect the opportunities and constraints that shaped these species in the first place. Yes, such experimentation may occasionally turn out badly. Heart surgery has risks, too. But the alternative is more frightening. Lacking the fruit of aggressive experimental field research, we will fail to be able to build the new habitats, the new natural communities, the new ecosystems that most wild species now need in order to survive for long. We will lose them.
Easing the pressure on set-asides
Even after we succeed at deploying a large variety of reconciled habitats all over the earth, our set-asides will retain great importance. For one thing, some species can pose a threat to people. We will often want to restrict fierce or annoying or disease-carrying species to reserves. A recent public brouhaha in Arizona about the fate of a puma (Felis concolor) roaming close to the edge of Tucson may not be unusual. “Kill ‘im,” said some. But our Governor Napolitano intervened and had ‘‘im’ captured and ‘transferred’ to another locale. (The ‘im turned out to be a ‘her.’) A short while later (16 May 2004), a less lucky lioness was gunned down by an Arizona and Fish Game officer for “stalking” people near a recreation site in a national forest close to the city.
Occasionally people do consent to be in harm’s way. In Nepal, for example, the World Wildlife Fund has an extensive project that works on behalf of tigers, rhinoceros and many other threatened but less dangerous vertebrates, all of which live intermingled with people and their enterprises despite the risk to local inhabitants (Dinerstein 2002). But in truth, the Nepalese people tolerate the dangerous wildlife because it helps them earn their livings in ecotourism and community forestry projects. The overarching rule remains: most of us will choose to be safe even though, regrettably, that might mean losing some truly magnificent species (Dinerstein 1998).
Yet some large reconciled places will be able to support fierce species without endangering people. Recall the cooling canals of the Turkey Point Power Plant. I must admit that I bridle at the prospect of crocodiles in my garden. But I do not mind them in those cooling canals. All things considered, the problems of the fierce, the annoying, and the pestilential may not be completely resistant to the ministrations of reconciliation.
Nonetheless, not all species will find homes in reconciled habitats. Reserves will provide the only habitats for inveterate, unreconcilable kulturmeider, the species that cannot do without set-asides. Kulturmeider are probably the truest endangered species. Maybe we ought to expand the definition of endangered species to include any that are kulturmeider - even if they now appear to have thriving populations. Certainly, we have long been aware that population size alone is inadequate to assess a species’ status. Populations can change quickly and dramatically, often over an order of magnitude. Witness the case of passenger pigeons, which declined from a population of ca. five billion to a population of zero within a century (Schorger 1955). And the abundant eelgrass limpet, Lottia alveola, totally dependent on a narrow band of salinity values, vanished in less than a decade when a disease destroyed its food in that particular habitat (Carlton et al 1991).
Reconciliation ecology eyes kulturmeider with a view to converting them into kulturfolger. Kulturfolger are the species that do live with us. (The German word is cognate to the English ‘culture follower’.)
Species conversion has happened, sometimes on purpose. Most cases involved the negative direction: kulturfolger to kulturmeider. But the positive direction has also occurred. For instance, people supplying nest boxes to eastern bluebirds (Sialia sialis) have converted no-bluebird-gardens into bluebird Edens (Davis and Roca 1995; North American Bluebird Society 2004).
Reconciliation ecology seeks to multiply the helpful conversion rate by several orders of magnitude. It would prefer that many of the new kulturfolger species be formerly threatened or endangered. But even if that does not happen and the new kulturfolger emerge from the ranks of unthreatened kulturmeider, at-risk species will benefit in two ways. Managers of reserves will be able:
to focus on the habitat requirements of threatened species and
to reduce competitive and predatory pressures on threatened species.
More intense focus will come because reserve management involves trade-offs: Improving habitat for one species often means degrading it for another. Relieved of the responsibility of satisfying the new kulturfolger, the manager will be free to maximize improvement for a kulturmeider species in trouble.
Reducing competitive and predatory pressure will result if society allows managers to reduce or even eliminate key kulturfolger in reserves. Competitive pressure on threatened species often comes from close relatives that are common and widespread. I believe many of these more common species are habitat-tolerant partners to their habitat-intolerant cousins. Hence, if we wish to help a threatened, habitat-intolerant species to the fullest extent possible, we may need to restrict the abundance of--or even to eliminate--the common species in some reserves. It sounds controversial and it is: reduce diversity at a small-scale in order to increase it at a larger one! But in a world of reconciliation, it may also be good science and make good public policy.
One can easily appreciate cases of excessive predation on kulturmeider in reserves. For example, in the autumn of 2002, I visited a spectacular reserve in New Zealand, a reserve that utterly depends upon the exclusion of predatory kulturfolger. Tiritiri Matangi is a 230-hectare (568-acre) island sanctuary in the Hauraki Gulf only 4 kilometers (2.5 miles) from the New Zealand mainland. Yet Tiritiri overflows with bird and plant species rarely seen today anywhere on the mainland. Some bird species (like the stitchbird ,Notiomystis cincta, and the saddleback ,Creadion carunculatus) are completely extinct on the mainland. One, a large, flightless gallinule called takahe (Porphyrio mantelli), parades in numbers around the island’s picnic spot although, from about 1900 to 1950, it was thought globally extinct. Bellbirds, North Island robins, whitefaces, brown teal, red-crowned parakeets, little spotted kiwi, fantail, tui, fernbird, spotless crake--they are all there. A visit to this reserve is a trip in a time machine back to the New Zealand of 150 years ago.
Tiritiri had been an ecological disaster. By 1983, 94 percent of its native woody vegetation had been cleared (Anonymous 2002). In the following decade, volunteers planted more than 250,000 trees. Then the New Zealand Department of Conservation began to get rid of many of Tiritiri’s common species, especially its introduced plants and mammals. The only mammal native to New Zealand is an extinct bat. All others--such as rats, mice, cats, possums and weasels–form part of a long list of deliberately introduced exotic plants, birds and even insects (two wasps), many of which have wreaked havoc on the native bird species.
Once rid of its mammals, Tiritiri became a haven into which many native bird species were successfully introduced. But one species, kokako (Callaeas cinerea), the scarce, blue-feathered and melodious “New Zealand crow,” which happens to be one of only two surviving members of an endemic New Zealand family, is having a problem with a native raptor, the Australasian harrier (Circus approximans).
Should people eliminate this harrier, this successful and widespread kulturfolger, from the island in order to ensure the future of the kokako? Simon Fordham (2001) thought so. But the several letters-to-the-editor in Dawn Chorus, the official newsletter of the Supporters of Tiritiri Matangi Inc. reflected a deep difference of opinion, a difference which is likely to characterize debates of this sort (Readers 2001). The harriers won the debate and the kokako may be disappearing. It was one thing to get rid of exotics; they are animate evil in the minds of many conservationists. It was quite another to accept the fact that a local population of a charismatic, native species also had to go. Let nature take its course, said the winning side. And she will.
Meanwhile, in the USA, another listed species was having trouble with a predator (Roemer and Donlan 2004). The island fox (Urocyon littoralis) lived only on six of the Channel Islands off the California coast. So, a century ago, did at least 24 breeding pairs of bald eagles (Haliaeetus leucocephalus)(Kiff 1980). By 1950, the bald eagles were gone, probably from eating fish contaminated by pesticides.
The bald eagles, primarily fish-eaters, were replaced by the mammal-eating golden eagle, protected by Congress in 1962. Golden eagles support themselves mostly by eating the feral pigs on Santa Cruz and Santa Rosa Islands. But by 1994 they were taking foxes, too. On Santa Cruz Island and nearby San Miguel Island, the fox population declined from 1312 and 350 (respectively) in 1993, to 133 and 15 adults in 1998; the population on Santa Rosa Island was also low (Roemer et al 2001). By summer 2002, 75 survived on Santa Cruz while both San Miguel’s and Santa Rosa’s foxes are extinct in the wild. (They survive in captive breeding programs.) (The Nature Conservancy 2003b). Extinction was smiling.
Channel Islands National Park is a nature reserve, like all US national parks. Santa Cruz Island does have some private property but it belongs to The Nature Conservancy, which is also devoted to the preservation of wildlife. What a dilemma the managers faced! Either stand by and watch a listed, endemic fox disappear or actively remove a protected, majestic eagle. Spurred by a combination of scientists and laypeople, they chose eagle removal.
Managers have so far moved 31 golden eagles from Santa Cruz Island to northeastern California (Coonan 2001; Coonan and Rutz 2003; The Nature Conservancy 2003c). To defend the islands against stray golden eagles that might wander across the channel from the mainland, they are also reintroducing bald eagles to Santa Cruz Island (The Nature Conservancy 2003a). Meanwhile, as many as ten trap-wary golden eagles still reside on the islands and hinder fox recovery (Roemer and Donlan 2004). Ensuring the survival of the fox might mean shooting these eagles. As Roemer and Donlan put it (p27), “Lethal removal of an emblematic bird like the golden eagle is... emotionally charged, politically unsavory and legally challenging.” Indeed, the very idea of tampering with eagle populations on a nature reserve in order to protect diversity is revolutionary. It risks evoking a clever but simplistic slogan such as the famous one so popular during the anti-Vietnam War era. (“Fighting for peace is like f...ing for chastity.”) But it is just the kind of new thinking we need to save the earth’s species.
The ESA of tomorrow will be much more effective if it embraces reconciliation ecology. But in no case should it oppose reconciliation either overtly or indirectly. To do so would condemn the Endangered Species Act to eventual failure.
Abramsky, Z., M.L. Rosenzweig, B. Pinshow, J.S. Brown, B. Kotler, and W.A. Mitchell 1990. “Habitat selection: An experimental field test with two gerbil species,” Ecology 71: 2358-2369.
Anonymous 2002. "Tiri Tiri Matangi Island." http://nzbirds.com/TiriTiriMatangi.html
Ashley, M.V., M.F. Willson, O.R.W. Pergams, D.J. O’Dowd, S.M. Gende, and J.S. Brown 2003. “Evolutionarily enlightened management,” Biological Conservation 111: 115-123.
Boal, C.W., and R.W. Mannan 1999. “Comparative breeding ecology of Cooper's hawks in urban and exurban environments,” Journal of Wildlife Management 62: 864-871.
Carlton, J.T., G.J. Vermeij, D.R. Lindberg, D.A. Carlton, and E.C. Dudley 1991. “The first historical extinction of a marine invertebrate in an ocean basin: the demise of the eelgrass limpet,” Biol. Bulletin 180: 72-80.
Coonan, T.J. 2001. Recovery plan for island foxes (Urocyon littoralis) on the northern Channel Islands. National Park Service, Channel Islands National Park, Ventura, CA.
Coonan, T.J., and K. Rutz 2003. Island Fox Captive Breeding Program 2002 Annual Report. National Park Service, Channel Islands National Park, Ventura, CA.
Coope, G.R. 1987. “The response of late Quaternary insect communities to sudden climatic changes,” In Organization of Communities Past and Present, edited by J.H.R. Gee, and P.S. Giller, 421-438 Blackwell Scientific, Oxford.
Cowling, R.M., G.E. Gibbs Russell, M.T. Hoffman, and C. Hilton-Taylor 1989. “Patterns of plant species diversity in southern Africa,” In Biotic Diversity in Southern Africa: concepts and conservation, edited by B.J. Huntley, 19-50 Oxford U Press, Cape Town.
Cowling, R.M., and D. Richardson 1995. Fynbos: South Africa's unique floral kingdom. Fernwood Press, Vlaeberg, South Afica.
Davis, M.B. 1983. “Holocene vegetational history of the eastern United States,” In Late-Quaternary Environments of the United States, edited by H.E. Wright, Jr., 166-181 Univ. of Minnesota Press, Minneapolis.
Davis, W.H., and P. Roca 1995. Bluebirds and their Survival. The University Press of Kentucky, Lexington, KY.
Denton, J.S., S.P. Hitchings, T.J.C. Beebee, and A. Gent 1997. “A recovery program for the natterjack toad (Bufo calamita) in Britain,” Conservation Biology 11: 1329-1338.
Dinerstein, E. 1998. “It takes a village,” Zoogoerhttp://natzoo.si.edu/Publications/ZooGoer/1998/2/ittakesavillage.cfm
Dinerstein, E. 2002. The return of the unicorns: a success story in the conservation of Asian rhinoceros. Columbia University Press, New York.
Environmental Defense 2004. "Safe Harbor Agreements by Date." http://www.environmentaldefense.org/article.cfm?ContentID=403
Fordham, S. 2001. “Editorial,” Dawn Chorus 45: 2. www.123.co.nz/tiri/Newsletters/Newsletter45.pdf
Gaby, R., M.P. McMahon, F.J. Mazzoti, W.N. Gillies, and J.R. Wilcox 1985. “Ecology of a population of Crocodylus acutus at a power plant site in Florida,” J. Herpetology 19: 189-198.
Kiff, L.F. 1980. “Historical changes in resident populations of California Islands raptors,” In The California islands: proceedings of a Multidisciplinary Symposium, edited by D.M. Power, Santa Barbara Museum of Natural History, Santa Barbara, CA.
MacArthur, R.H., and E.O. Wilson 1963. “An equilibrium theory of insular zoogeography,” Evolution 17: 373-387.
MacArthur, R.H., and E.O. Wilson 1967. The Theory of Island Biogeography. Princeton University Press, Princeton, NJ.
MacMullin, S. 2004. “Notice of availability of a Safe Harbor agreement for topminnow and pupfish in Arizona and receipt of application for incidental take permit for the Arizona Game and Fish Department,” Federal Register 69: 15362. http://a257.g.akamaitech.net/7/257/2422/14mar20010800/edocket.access.gpo.gov/2004/pdf/04-6674.pdf
Mannan, R.W., and C.W. Boal 2000. “Home range characteristics and habitat selection of male Cooper's hawks in an urban environment,” Wilson Bulletin 112: 21-27.
National Research Council 1995. Science and the Endangered Species Act. National Academy Press, Washington, DC.
National Wildlife Federation 2004. "Backyard Wildlife Habitat." http://www.nwf.org/backyardwildlifehabitat/
North American Bluebird Society 2004. http://www.nabluebirdsociety.org
Pauly, D. 1995. “Anecdotes and the shifting baseline syndrome of fisheries,” Trends in Ecology & Evolution 10: 430.
Peters, R.L., and J.D.S. Darling 1985. “The greenhouse effect and nature reserves,” Bioscience 35: 707-717.
Pimm, S.L., M.L. Rosenzweig, and W. Mitchell 1985. “Competition and food selection: field tests of a theory,” Ecology 66: 798-807.
Preston, F.W. 1960. “Time and space and the variation of species,” Ecology 41: 785-790.
Readers 2001. “Letters to the editor,” Dawn Chorus 46: 12. www.123.co.nz/tiri/Newsletters/Newsletter46.pdf
Roemer, G.W., T.J. Coonan, D.K. Garcelon, J. Bascompte, and L. Laughrin 2001. “Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox,” Animal Conservation 4: 307-318.
Roemer, G.W., and C.J. Donlan 2004. “Biology, policy and law in endangered species conservation: I. The case history of the island fox on the northern Channel Islands,” Endangered Species Update 21: 23-31.
Rosenzweig, M.L. 1973. “Habitat selection experiments with a pair of coexisting heteromyid rodent species,” Ecology 54: 111-117.
Rosenzweig, M.L. 1981. “A theory of habitat selection,” Ecology 62: 327-335.
Rosenzweig, M.L. 1991. “Habitat selection and population interactions: the search for mechanism,” American Naturalist 137: S5-S28.
Rosenzweig, M.L. 1995. Species Diversity in Space and Time. Cambridge University Press, Cambridge, UK.
Rosenzweig, M.L. 1999a. “Heeding the warning in biodiversity's basic law,” Science 284: 276-277.
Rosenzweig, M.L. 1999b. “Species diversity,” In Advanced Theoretical Ecology: principles and applications, edited by J. McGlade, 249-281 Blackwell Science, Oxford, UK.
Rosenzweig, M.L. 2001. “Loss of speciation rate will impoverish future diversity,” Pr. Nat. Acad. Sci. (USA) 98: 5404-5410. http://www.pnas.org/cgi/reprint/98/10/5404.pdf
Rosenzweig, M.L. 2003a. "The Careful Foot." http://www.reconciliationecology.com
Rosenzweig, M.L. 2003b. “Reconciliation ecology and the future of species diversity,” Oryx 37: 194-205.
Rosenzweig, M.L. 2003c. Win-Win Ecology: How the Earth's Species Can Survive in the Midst of Human Enterprise. Oxford University Press, New York.
Rosenzweig, M.L., and E.A. Sandlin 1997. “Species diversity and latitudes: listening to area's signal,” Oikos 80: 172-176.
Schorger, A.W. 1955. The Passenger Pigeon: its natural history and extinction. Univ. of Wisconsin, Madison.
Shore, D., and S. Packard 2000. “A green vision for Chicago,” Chicago Wilderness Magazine. http://chicagowildernessmag.org/issues/spring2000/greenchicago.html
Strahan, R. 1983. The Australian Museum Complete Book of Australian Mammals. Angus & Robertson, North Ryde, NSW.
Terman, M.R. 1997. “Natural links: naturalistic golf courses as wildlife habitat,” Landscape and Urban Planning 38: 183-197.
The Nature Conservancy 2003a. "Santa Cruz Island: Bringing Back the Bald Eagle." http://nature.org/wherewework/northamerica/states/california/preserves/art9830.html
The Nature Conservancy 2003b. "Santa Cruz Island: Foxes, Pigs, and Eagles." http://nature.org/wherewework/northamerica/states/california/preserves/art9827.html
The Nature Conservancy 2003c. "Santa Cruz Island: Relocating Golden Eagles." http://nature.org/wherewework/northamerica/states/california/preserves/art9829.html
Tufts, C., and P. Loewer 1995. Gardening for Wildlife. Rodale Press, Emmaus, PA.
Vuilleumier, F. 1970. “Insular biogeography in continental regions. I. The northern Andes of South America,” Amer. Natur. 104: 373-388.
Wilcove, D.S., M.J. Bean, R. Bonnie, and M. McMillan 1996. Rebuilding the Ark - toward a more effective endangered species act for private land. Environmental Defense Fund, New York.
Williams, S.E., E.E. Bolitho, and S. Fox 2003. “Climate change in Australian tropical rainforests: an impending environmental catastrophe,” Proc. Royal Soc. London B 270: 1887-1892.
Wilson, E.O., and E.O. Willis 1975. “Applied biogeography,” In Ecology and Evolution of Communities, edited by M.L. Cody, and J.M. Diamond, 522-534 Belknap Press of Harvard Univ. Press, Cambridge, Mass.