In just the past thousand years, our increased population and ability to alter habitats around the globe has hit Earth like an asteroid.
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When I teach introductory biology at the University of Washington, we have about fifty minutes to discuss conservation biology. So to give my students a feel for what is happening to biodiversity around the globe, I ask them to apply some of the same mathematical relationships we used the week before to analyze how populations grow through time. For example, if you put $100 in the bank, allow it to earn interest, and find that you have $105 a year later, the annual growth rate of your money is calculated as 105/100, which simplifies to 1.05. The increase is 0.05, or 5 percent, of the original amount. If you left the money alone to continue accumulating interest at the same rate year after year, you could calculate how much money you’d have after a given number of years. The amount of money present at the start of each year gets multiplied by 1.05 to figure out how many dollars you’ll have at the end of the year. You do this twenty times to figure out the total after twenty years, fifty times to figure out the total after fifty years, and so on.
Then I ask my students to use the same logic to figure out the growth rate of the number of threatened and endangered species. To do this I show them data on the annual census of threatened and endangered organisms worldwide. The numbers come from the most highly respected agency involved in tracking how species are doing: the International Union for the Conservation of Nature, or iucn, headquartered in London. The scientists who contribute to iucn’s annual listings use objective and verifiable measures to determine whether a particular species should be considered threatened or endangered. As I write this, iucn has published fifteen comprehensive assessments over a span of seventeen years. The total number of threatened and endangered species has changed as follows:
1998: 10,553
2000: 11,046
2002: 11,167
2003: 12,259
2004: 15,042
2006: 16,117
2007: 16,308
2008: 16,928
2009: 17,291
2010: 18,351
2011: 19,570
2012: 20,219
2013: 21,288
2014: 22,413
2015: 22,784
To summarize, the number of species that are in trouble grew from 10,553 in 1998 to 22,784 in 2015. Averaged over the seventeen-year period, this is a rate of increase of 1.046—close to the 1.05 annual growth rate of our bank balance, amounting to 5 percent interest. To help my students interpret this number, I point out that iucn and other authorities estimate that there are 1,560,000 species living today (not including the millions of species in the lineages called bacteria and archaea, simply because they are too poorly studied). If a mass extinction occurred, it would mean that 60 percent of these get wiped out. Sixty percent of 1,560,000 is 936,000.
And then we get to the question of the day: If the rate of 1.046 continues, how long will it take for the number of threatened and endangered species to reach 936,000 from the starting point of 22,784? When the students do the appropriate plugging and chugging, the answer turns out to be about eighty-three years. I point out that if this is so, it means their grandchildren will live to see the sixth mass extinction in the history of life.
You can argue—strenuously—with the “if this is so” statement. For example, it’s almost undoubtedly true that iucn’s estimate of more than twelve thousand species becoming threatened in seventeen years is inflated by what researchers call ascertainment bias. You’re probably familiar with this issue; ascertainment bias is responsible for at least part of the recent spike in the percentage of children afflicted with autism spectrum disorders. We’re finding more kids with autism, and more species in trouble, because we’re looking harder.
Ascertainment bias is important because the eighty-three-years-to-a-mass-extinction conclusion is extremely sensitive to even small changes in the rate of growth of the number of species that are in trouble. You could also object to the assumption that all of the species classified as threatened or endangered, now or in the future, will actually go extinct. After all, we have dozens or hundreds of well-documented comeback stories.
But your analysis shouldn’t stop there. For example, I ask my students to think back to the data that they (and you) examined on projections for human population growth, and then I ask whether the pressure on natural areas is likely to be the same in the year 2100 as it was from 1998 to 2015. Most predict that the rate of habitat destruction, and thus the rate of growth of the number of endangered species, is likely to rise. And you could bring up other issues: the total of 22,784 species on the threatened list in 2015 doesn’t include the estimated thousand bird species that researchers found recently extinct in Polynesia, or the dodo or auk or passenger pigeon, or the hundreds or thousands of large mammal and bird species—ranging from mastodons and mammoths to Irish elk and moas—that went extinct with our help at the end of the Ice Age. Or that even if the estimate of eighty-three years is off by a factor of 1000, we’re still far under the 60-percent-gone-in-a-million-years criterion to qualify as a mass extinction.
Finally, I give my students citations to papers that use other sources of data to address the same question. An array of research teams using different sources of data and a variety of computer models came to the same conclusion independently: the sixth mass extinction in the history of life may be under way.
The key word is may. We may be on a trajectory to a mass extinction, but that doesn’t mean we have to end up there. Beavers have dodged a bullet in North America and in Europe; we’ve pulled sandhill cranes and grizzly bears and bald eagles and bison back from the brink of extinction. With more restoration efforts like Tarboo Creek and with global action on climate change and human population growth, there’s a chance other threatened species have a future as well.
Wild Things
The first full-time job I had out of college, outside of doing carpentry work, was running education and exhibits programs for a little conservation organization called the International Crane Foundation. The group was started by two graduate students who had been studying crane behavior at Cornell University. The two got involved in conservation efforts early in their research careers because seven of the fourteen crane species were endangered at the time. The foundation did field research on four continents; worked to get wetlands set aside as crane refuges in India, Japan, and Korea; and was breeding as many of the species as possible in captivity. They eventually began releasing offspring back to the wild to supplement declining populations or restore lost ones.
It was exciting to be part of an organization in its formative years, though I’ll never forget asking the administrator for paper clips and being asked how many I needed so that she could count them out. The most enduring benefit for me was the practice I got teaching—I had to present several hundred public programs each year.
These talks and workshops were an exercise in Aristotle’s rhetoric—the art of persuading people to your point of view. I had to convince people that the Crane Foundation was a dynamic, innovative, and effective organization worthy of support. More generally, I had to sell the idea that conservation is good and that it’s something people from all walks of life can and should embrace. The tools at my disposal were humor, ribald bird stories (often involving efforts to collect semen from cranes for artificial insemination), and the foundation’s long string of successes at protecting wild places.
Of the five or six hundred talks I gave, though, I remember one best. It was a lunchtime presentation to the Rotary Club in Sauk City, Wisconsin. Because my father was a Rotarian, I knew my audience: doers—mostly small business owners—who were committed to their community. So I pulled out all the stops with slides and stories, and ended in what I thought was a blaze of glory. Then came the first question: “Why should we care if cranes go extinct or not?”
It was like throwing a light switch. The room’s atmosphere went from bright to da
rk.
Some of the Rotarians looked upset and embarrassed, but I was sympathetic to the audience member. It’s a question I was asking myself almost every morning. At the time, our family’s income was so low that we qualified for public assistance. We were eating what my grade school friends called commodity cheese, and we didn’t have health insurance. I often asked myself what I was doing.
Aldo Leopold said there are some people who can live without wild things, and some who cannot. I’m not sure that his claim is actually true, given recent research. Experiments have shown that hospital patients heal better when they can see the outdoors, and people who walk in a natural setting have better mental health indicators than similar people who walk in urban settings. An observational study suggests that kids who grow up near green spaces have better cognitive development than kids from comparable backgrounds who don’t. But all evidence to the contrary, I have friends, neighbors, and family who are convinced they can live without wild things, and I suspect that almost nothing could persuade them otherwise. If the man who asked the question was like them, there probably wasn’t much I could do or say. But I had to try. So I acknowledged the issue as an important one and said I’d come up with three reasons.
The first was practical. The Crane Foundation was really in the business of preserving wetland ecosystems—the birds were just a way to get peoples’ attention. In addition to hosting wildlife, intact wetlands minimize flood damage, regenerate groundwater, and purify surface water. They perform important public services and save us money. If the United States had been smart about protecting wetlands as its cities developed, we’d be saving hundreds of lives and many billions of dollars in flood insurance and flood-induced repair bills every year.
My second reason was ethical. The people I admire most take responsibility in their work, and in their communities and families. They make things better by giving something back to the world. They also live a moral life. The essence of morality is to care for things other than yourself, treat other people and living things with respect, and use power wisely when you have it. Biological and cultural evolution has now put human beings in a position of immense power relative to other species, and we can be destroyers or stewards. This is a moral choice. I view practicing conservation as a matter of goodness, of doing the right thing. It is wrong to harm a species or an ecosystem. If we are the reason cranes and other species are going extinct, we need to take responsibility and act on their behalf.
The third and final reason was more personal. It was aesthetic, even spiritual. People enjoy living in places like Sauk City because they are beautiful. The town is surrounded by productive, well-managed, family-owned farmland and rolling woodlands that are large and intact enough to support important populations of rare birds and mammals. Dozens of bald eagles spend the winter along the Wisconsin River just north of town. I asked the group to imagine how poor their lives would be without these things—if they lived in a world of factory farms and asphalt. Fundamentally, I said, we work to save cranes and wetlands for the same reason we work to help our communities, friends, spouses, and children: because we love them.
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More than thirty years have gone by since that afternoon in Sauk City. I’ll never know whether I made an impression, positive or negative, on the questioner. But during this span, ecologists have done hundreds of experiments to test my first claim—that conservation has practical benefits. The initial question was whether natural communities with many different species function better than the same areas with fewer species. The motivation was simple: researchers realized that we are losing many organisms to extinction and wanted to know if it matters biologically.
The first papers summarized experiments in prairies. The basic scheme was to set up an extensive array of experimental plots in the same area, sow different numbers of grasses and other flowering plants in each, let everything grow for a couple of years, and then measure productivity—the grams of biomass, or green stuff. For practical reasons the researchers had to ignore what was going on with root growth and limit themselves to measuring aboveground biomass. What they found, in experiment after experiment, is that productivity increased with the number of species present in each study plot until a saturation point was reached. The result was important because plant biomass is what everyone else, from fungi to bison, eats. In general, productive plant communities support a larger number and more diverse array of animals.
These studies were quantifying what biologists and economists now call ecosystem services—the “goods” natural areas deliver to humans and other species. In the 1930s, Aldo Leopold wrote about the same thing but called it land health. The problem that he and other ecologists had at the time was quantifying what they meant by health—coming up with objective, rigorous ways of testing the hypothesis that species-rich areas work better than species-poor ones. Although the soil erosion problems of the Dust Bowl years were starting to open some eyes, at that time almost no scientific evidence existed on the question of whether species diversity matters. Rather, it was an article of faith that leaving some areas undisturbed would provide tangible benefits for humans. And in general, the idea of managing land for something other than the maximum and most immediate economic gain was new, revolutionary, and largely untested.
More recent experiments have documented that when a drought or other disturbance occurs, productivity declines less in species-rich habitats than in species-poor areas. Places with high species diversity also tend to recover from disturbance faster, resist invasion by exotic species better, and sop up more carbon dioxide from the atmosphere. The broad implication here is that a mass extinction will make Earth less stable and productive.
It’s unlikely, though, that this research will inspire people to do the things it will take to preserve biodiversity: limit family size, favor locally grown food, prefer smaller and more efficient homes, transfer the time and money spent on driving to more enjoyable activities, and contribute to the preservation of wild places through taxes and private donations.
Scientists are trained to be persuaded by data, but for most people it’s not about the evidence. It’s about values: what we want and what we think is good.
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The why-care question from Sauk City will get more common as today’s generation grows up. Since the late 1980s there has been a slow and steady decline in the probability that an average American will visit a national park, state park, or national forest. The same trend occurs in the proportion of people buying a fishing license or duck stamp. The number of hunters is holding steady—perhaps because deer populations have exploded in many parts of the United States. The same downward trend in national park visitation is occurring in Japan, the only other major industrialized country for which data are available. Both of these analyses have controlled for changes in population size: even though the total number of visitors may be up in some areas, the overall percentage of people who seek out direct experiences with nature is declining.
If people care about things they love, and if a love of the outdoors grows from contact and experience, a smaller and smaller subset of the overall populace can be expected to extend themselves to save patches of the natural world.
This realization hit home a few years ago after a series of planning meetings for the Seattle Parks Department. I was part of a citizens’ group that was advising on the design of a new park being created from a recently decommissioned U.S. Navy air station. The Parks Department and the designers were proposing an intensive-use area with lighted playing fields next to a low-impact area with what would become one of the largest wetland restorations in western Washington. Our boys were playing soccer and baseball at the time, so my official capacity at the design meetings was to represent the needs of youth sports organizations. But I was thrilled with the wetlands proposal as well—it would be a great place for people to stroll and bird-watch, and wonderful shallow-water habitat next to the deeper-water environments of nearby Lake Washington.
/> At one particular meeting, the people advocating for the wetlands had been rhapsodizing about the amount of frog habitat that would be created. The other ball fields person there was nonplussed. “What,” he asked as we left, “is the big deal about frogs?”
I thought of him recently when I opened the door of our toolshed at Tarboo Creek and grabbed a box of galvanized nails from a shelf. Crouching in the corner, no longer in shadow, was a northern Pacific tree frog—a black-masked creature about an inch and a half long. You already know its call; it gives the classic “ribbit” that movie producers use in soundtracks for night scenes. The little frog in the shed was khaki colored, blending in with the wood shelf and walls. But out in the restoration area, not a stone’s throw away, I’d just found a grass-green tree frog of about the same size. Tree frogs can change color to match their background. They’re not as fast as a chameleon, but they will change before your eyes if you are patient enough to sit and watch for ten to fifteen minutes. I love the ’tweener stage best, when they’re not brown and not green but a mottled neither-nor.
We hear tree frogs almost every month of the year at Tarboo. On cold autumn or even winter nights, the odd call will sound out of nowhere, from somewhere high in a bigleaf maple tree. We remark on the one brave soul out in the darkness, body chilled to air temperature but still managing one unanswered call before quieting for the night. Then in spring, we use the volume of the frog chorus to track the temperature in the two ponds on the hill above the creek. Susan and I both grew up in the Midwest, so we experienced spring as a two-week orgy of budding, buzzing, and bursting before the forest canopy snapped shut with leaf-out and summer set in. But spring in the Pacific Northwest is a three-month marathon, with the temperature inching along day by day and week by week: two degrees forward and one degree back. The frog chorus is an audio thermometer, letting you know how things are going. On cool nights the calls are sporadic, as if cued by a conductor beating time and then pointing at random intervals around the orchestra. When warmth comes, though, everyone sings all at once and as fast as possible, so the calls swell and blend into one throbbing nightlong aria. We tiptoe along the path next to the ponds, arm in arm, trying to get close enough to pick out individual calls near our feet. Invariably, we do something that shuts down the chorus, bringing sudden silence. We never know what it is; sometimes the chorus quiets as we stand stock still, barely breathing. It can be many minutes before one courageous, love-struck male breaks the stillness. Then others join in—sporadically at first but with voices growing in frequency and volume as confidence builds. At last the assembly relaxes and throws itself back into the business of calling and mating.
Saving Tarboo Creek Page 14