Flood control in the USA

A  Americans have always feared floods, and with good reason. Floods are the most common and costly of the large natural disasters affecting the United States. Approximately 9 of every 10 presidential disaster declarations are associated with them and, after total insurance losses from a series of devastating floods between 1990 and 1997 reached nearly $34 billion, government policy changed. The USA has subsequently spent even more than that trying to control floods by building structures such as levees and dams to modify the ways rivers flow.

B  However, although we are well aware of the damage floods do, we have not, until recently, fully appreciated the many beneficial aspects of flooding. Floods are critical for maintaining and restoring many of the functions provided to humans by ecosystems. Among other things, regular flooding ensures high levels of diversity in the riverine environment by providing a critical habitat for fish, waterfowl, animals, insects, and plants. Floodwaters also replenish agricultural land with key nutrients vital to crop production, and transport the sediment that is necessary to maintain downstream delta and coastal land and prevent erosion. As our knowledge of floods has deepened, it has become apparent that floods present us with a paradox. On the one hand, we want to prevent them, because they threaten our lives and ways of life. On the other hand, we find ourselves searching for ways to allow or even reintroduce flooding, because it supports the biological infrastructure that makes valued aspects of our lives possible.

C  The focus of policy began to change dramatically in the wake of massive flooding in the upper Mississippi and lower Missouri river basins from June to August of 1993. Many of the flood defenses failed during this episode. In response, the President ordered a special committee to investigate causes, explore how human actions might have exacerbated the situation, and determine what the nation should do to prevent a repeat event. Known as the Galloway Report, the committee’s findings and recommendations marked the first time that the crucial ecological protections provided by wetlands and upland forests were explicitly acknowledged. This included their ability to store water, slow its entry into the river system, and absorb excess nutrients. The committee pointed out that losing these protections through changes in land use significantly increases runoff from farmland with serious consequences for water quality. Above all, the report acknowledged that floods are recurring phenomena that must be accepted and anticipated.

D  A common theme in the findings from analyzing a range of flood episodes is the importance of connections between riverine ecosystems, their floodplains, and the broader landscapes through which they flow. It is worth noting that efforts to prevent rivers from reclaiming their floodplains rarely pay off in the long run. On the contrary, most of the flood costs over the past decade have been associated with damage to structures in those floodplains. We have also learned that building on floodplains harms wetlands by reducing their ability to hold water and retain nitrogen, phosphorus, and other contaminants. Floodplains are the sole safeguard the environment has against these and other harmful effects of floods. The aftermath of flooding caused by storm Alberto in Georgia in 1994 highlighted the important role they play in minimizing destruction. When floodwaters entered agricultural fields, picking up soil particles contaminated with herbicides, pesticides, and fungicides, the large, forested floodplains in the area filtered out those particles. They never entered rivers to cause harm.

E  Fortunately, although the mechanics of re-establishing floodplains are daunting, it is not impossible; their ecosystems are resilient, as studies on recurrent floods in the lower Missouri River have shown. Annual spring floods have long been controlled in this portion of the river, which stretches from Sioux City, Iowa, to St. Louis, Missouri. As a result, it was almost totally disconnected from its floodplain and, by 1990, state or federal agencies had classified 16 fish species, 7 plant species, 6 insect species, 2 mussel species, 4 reptile species, 14 bird species, and 3 mammal species within the floodplain complex as endangered, threatened, or rare. But the situation began to change with the great Midwest floods of 1993, 1995, and 1996. Post-flood studies have demonstrated that plants, zooplankton, aquatic insects, fish, turtles, and other animals immediately exploited the reconnection with the floodplain.

F  Ensuring that the necessary changes in the landscape are actually made requires a good deal of thought, however. In particular, the fragmentation and lack of coordination that has characterized policy concerning floodplains in the United States must be addressed. Decisions on developments such as construction that could affect floodplains are made primarily at county and municipal levels, yet the current policy structure gives the federal government the most responsibility for floodplain management. It provides little incentive and few mechanisms for the county and municipal governments to help. Nor do individual states have much opportunity to become involved, even though they may be best situated to coordinate the diverse actions and decisions that are needed. In the end, all such policy decisions and the accompanying management actions must be based on people weighing up the costs and benefits of different spending priorities. In other words, they are political. Scientists alone will not, and should not, select which options are appropriate. Rather, their contribution will be to spell out the implications and the trade-offs of different policy options and management scenarios.

Songs of ourselves

A  Music is one of the human species’ relatively few universal abilities. Without formal training, any individual, from Stone Age tribesmen to suburban teenagers, has the ability to recognize music and, in some fashion, to make it. Why this should be so is a mystery. After all, music isn’t necessary for getting through the day, and if it aids in reproduction, it does so only in highly indirect ways. Language, by contrast, is also everywhere but for reasons that are more obvious. With language, you and the members of your tribe can organize a migration across Africa, build reed boats and cross the seas, and communicate at night even when you can’t see each other. In all its technological extravagance, modern culture springs directly from the human talent for manipulating symbols and syntax. Scientists have always been intrigued by the connection between music and language. Yet over the years, words and melody have acquired a vastly different status in the lab and the seminar room. While language has long been considered essential to unlocking the mechanisms of human intelligence, music is generally treated as an evolutionary frippery -- mere auditory cheesecake, as the Harvard cognitive scientist Steven Pinker puts it.

B  But thanks to a decade-long wave of neuroscience research, that tune is changing. A flurry of recent publications suggests that language and music may equally be able to tell us who we are and where we’re from -- not just emotionally, but biologically. And in an article in the August 6 issue of the journal Neuroscience, David Schwartz, Catherine Howe, and Dale Purves of Duke University argued that the sounds of music and the sounds of language are intricately connected. To grasp the originality of this idea, it’s necessary to realize two things about how music has traditionally been understood. First, musicologists have emphasized that while each culture stamps a special identity onto its music, music itself has some universal qualities. For example, in virtually all cultures, the sound is divided into some or all of the 12 intervals that make up the chromatic scale -- the scale represented by the keys on a piano. For centuries, observers have attributed this preference for certain combinations of tones to the mathematical properties of sound itself. Some 2,500 years ago, Pythagoras was the first to note a direct relationship between the harmoniousness of a tone combination and the physical dimensions of the object that produced it. For example, a plucked string will always play an octave lower than a similar string half its size and a fifth over a similar string two-thirds its length. This link between simple ratios and harmony has influenced music theory ever since.

C  This music-is-math idea is often accompanied by the notion that music, formally speaking, exists apart from the world in which it was created. Writing recently in The New York Review of Books, pianist and critic Charles Rosen discussed the long-standing notion that while painting and sculpture reproduced at least some aspects of the natural world and writing describes thoughts and feelings we are all familiar with, music is entirely abstracted from the world in which we live. Neither idea is right according to David Schwartz and his colleagues. Human musical preferences are fundamentally shaped not by elegant algorithms or ratios but by the messy sounds of real life and of speech in particular -- which, in turn, is shaped by our evolutionary heritage. ‘The explanation of music, like the explanation of any product of the mind, must be rooted in biology, not in numbers per se,’ says Schwartz.

Schwartz, Howe, and Purves analyzed a vast selection of speech sounds from a variety of languages, to reveal the underlying patterns common to all utterances. In order to focus only on the raw sound, they discarded all theories about speech and meaning and sliced sentences into random bites. Using a database of over 100,000 brief segments of speech, they noted which frequency had the greatest emphasis on each sound. They discovered that the resulting set of frequencies corresponded closely to the chromatic scale. In short, the building blocks of music are to be found in speech.

Far from being abstract, music presents a strange analog to the patterns created by the sounds of speech. "Music, like the visual arts, is rooted in our experience of the natural world," says Schwartz. "It emulates our sound environment in the way that visual arts emulate the visual environment." In music we hear the echo of our basic sound-making instrument -- the vocal tract. The explanation for human music is simpler still than Pythagoras’s mathematical equations: We like the sounds that are familiar to us, we like sounds that remind us of us. This brings up some chicken-or-egg evolutionary questions. It may be that music imitates speech directly, the researchers say, in which case it would seem that language evolved first. It’s also conceivable that music came first, and language is, in effect, an imitation of song -- that in everyday speech, we hit the musical notes we especially like. Alternately, it may be that music imitates the general products of the human sound-making system, which just happens to be mostly speech. "We can’t know this," says Schwartz. What we do know is that they both come from the same system, and it is this that shapes our preferences.

D  Schwartz’s study also casts light on the long-running question of whether animals understand and appreciate music. Despite the apparent abundance of "music" in the natural world -- birdsong, whale song, wolf howls, synchronized chimpanzees -- previous studies have found that laboratory animals don’t show a great affinity for the human variety of music making. Marc Hauser and Josh McDermott of Harvard argued in the July issue of Nature Neuroscience that animals don’t create or perceive music the way we do. The fact that laboratory monkeys can show recognition of human tunes is evidence, they say, of shared general features of the auditory system, not any specific chimpanzee musical ability. As for birds, those most musical beasts, they generally recognize their own tunes and narrow repertoire but don’t generate novel melodies like we do. There are no avian Mozarts.

But what’s been played to the animals, Schwartz notes, is human music. If animals evolve preferences for sound as we do -- based upon the soundscape in which they live -- then their "music" would be fundamentally different from ours. In the same way that our scales derive from human utterances, a cat’s idea of a good tune would derive from yowls and meows. To demonstrate that animals don’t appreciate sounds the way we do, we’d need evidence that they don’t respond to "music" constructed from their own sound environment.

E  No matter how the connection between language and music is parsed, what is apparent is that our sense of music, even our love for it, is as deeply rooted in our biology and in our brains as language is. This is most obvious with babies, says Sandra Trehub at the University of Toronto, who also published a paper in the Nature Neuroscience special issue. For babies, music and speech are on a continuum. Mothers use musical speech to "regulate infant emotional states," Trehub says. Regardless of what language they speak, the voice all mothers use with babies is the same: something between speech and song. This kind of communication puts the baby in a trance-like state, which is probably not very surprising. The upshot, says Trehub, is that we probably don’t realize just how much of a necessity music is.