Is there a better dream than the glorious life of a songbird, gliding over the land from tree to tree, diving into flower gardens, splashing in a pool, and joining hundreds in a chorus with scores of parts? Home may be the luxuriant tropics where life is always sunny. Your ancestors gave you genes for the marathon, when you migrate to foreign land with an explosion of delicious insects or seeds, nice for raising babies. After several nights of flying, an inhospitable metro area stretching to the horizon appears beneath you. But look, a large green patch ahead … and tired wings thankfully carry you there for rest and food (Figure 12.1). While foraging, you meet an unknown relative who grew up in forest beyond the city. The local bird reached your greenspace by moving along a wonderfully wide green corridor, connecting natural land to city center.

Many types of large greenspaces and major green vegetated corridors are introduced in this chapter. The vegetation within them appears in six general forms (Dorney and McClellan, 1984; Kot, 1988; Godde et al., 1995; Rieley and Page, 1995; Breuste, 2009). Examples of each are listed:

1. Woods: woodland, forest, natural, semi-natural, remnant, regenerated, all normally containing litter, herbaceous, and shrub layers.

2. Lawn with trees: cemetery, golf course, city park, playing field area, and plaza, most containing ornamentals, shrubs, dispersed trees, and flower gardens.

3. Urban agriculture: crops/cultivation, paddy, pasture, orchard/vineyard, and community garden.

4. Wetland: freshwater or saltwater mudflat, marsh, swamp.

5. Successional habitat: meadow, edge of dump, former farm field, former quarry, vacant plot, brownfield.

6. Combination of the preceding types: considerable habitat diversity, and often the most common form of greenspace vegetation.

We daily bathe in urban air. So does everything else in built areas. The nature of this air overwhelmingly depends on microclimate and pollutants, which in turn are strongly determined by the built environment.

Consider the urban trees and other plants that bathe continuously outdoors. Individual trees, tree lines and woods, plus mowed grass, low spontaneous plant cover and ornamental plantings, are the prime vegetation types found repeatedly across urban areas. Individual shrubs are common, though shrubby areas tend to be uncommon despite their ecological importance (Forman, 2008).

The term “urban revolution” was introduced by Gordon Childe in 1936 to highlight the powerful process of transforming agricultural societies to large complex urban centers. His model describes how communities, beginning around 9000 years ago, grew from tens or hundreds to thousands of people. In 3100 BC, Memphis, Egypt was the largest city in the world with over 30 000 residents. Today, the Cairo metropolitan area has over 17 million inhabitants and ranks 15th on the list of the world’s largest cities. Mega-cities such as Tokyo, Seoul, Mexico City, and New York have over 20 million urban dwellers and continue to grow. The scale and complexity of the urbanization process originally depicted by Childe has little resemblance to what is happening today.

In the short history of humans on our planet, the number, population size, spatial extent, rate of growth, and degree of environmental impact of cities are unprecedented. Today, cities and towns face a myriad of formidable environmental challenges concerning food production, energy, water, waste management, and pollution, as well as social challenges in regard to jobs, poverty, and human health and wellbeing. I propose that as a result of the current rate and magnitude of urbanization around the globe, we are on the cusp of a new “urban revolution.” The goal and rallying call of this revolution is “We Want Healthy, Liveable, Sustainable, and Resilient Cities and Towns.”

Suppose a chemical was accidentally released into the air and killed all the plants in a city. Would it matter? Would the city look slightly different, or fundamentally different? Would almost everyone leave?

Or perhaps only certain types of plants died – trees, flowers, or native species. Or, in only certain habitats – lawns, street trees, or woodlands. Or, it prevented flower formation, seed germination, or shrub growth. Or it cut biodiversity by 90%, or tripled the number of species. Or vegetation change slowed, or accelerated, tenfold. Or areas were hit at different intensity, reconfiguring the vegetation patterns of the urban landscape. While these are extreme examples, they point to many of the key patterns, processes, and changes to be explored in this chapter.

Imagine a glorious day in your favorite city being energized at every turn. Sparkling clear air. Hardly any traffic. People alive, interesting. Appealing architecture and gardens (Figure 1.1). Amazing cultural events. Delightful diverse shopping. Food the best. Saw everything … relished it all.

Suddenly a friend appears, an ecologist. Comparing notes, she or he is equally enthusiastic. Luxuriant native street trees with lots of lichens. Clear water in the city pond. Bicycle routes and long walking routes busily used. Songbirds zipping along a shrubby tree strip between parks. No dog droppings. Wind blowing the smokestacks’ noxious air out of the city. Green walls and balconies facing each other over streets. Restaurants with rat-proof dumpsters. Elongated grass-and-flower depressions for riverside floodwaters. The intriguing list goes on. Chuckling, together you have seen almost everything, yet seemingly in two different cities.

Once again we explore the core of urban ecology. This time built structures, interacting with organisms and the physical environment, play the leading roles (Bartuska and Young, 1994). Concentrated urban roads and buildings represent a pinnacle of human engineering and architecture, indeed construction.

Hard straight lines, rectangles, grids, and other patterns close to Euclid’s geometry predominate. Such patterns, providing many benefits to people packed together, contrast with more natural lands worldwide mainly displaying the soft curves of nature. Yet even the casual observer will notice and feel nature throughout the densest parts of city centers, commercial areas, and high-rise residential areas. Here the hard lines provide contrast to the irregular curves, or vice versa. Indeed, the two forms are well intertwined in urban areas.

Following our journey through the rich patterns, delights and surprises in urban ecology, let us reflect, even speculate, a bit. I have chosen a handful of themes to explore that seem to be of particular interest and importance now and for the future. Let us consider urban ecology and the (1) distributions of aggregated people; (2) greenspaces and park system; (3) habitat heterogeneity and biodiversity; (4) tight urban water system; (5) ecological l ows and urban networks; (6) urban change; and (7) societal goals and applications of urban ecology. In rel ecting on these big subjects, my goal is to crack them open enough to catalyze further and useful pondering for scholars and for society.

1. And drink pure water from the pump,

2. I gulp down infusoria

3. And quarts of raw bacteria,

4. And hideous rotatorae,

5. And wriggling polygastricae,

6. And slimy diatomacae,

7. And various animalculae

8. Of middle, high and low degree.

9. William Juniper, The True Drunkard’s Delight, 1933

Some years ago I tried to call the “National Center for Urban Wildlife” in Washington, D.C. and after futile attempts to find the number, the telephone operator said politely, “Sir, are you really serious?” While cities may be hot spots of human wild life, I was thinking of urban wildlife, the non-domesticated terrestrial animals in urban areas (Goode, 1986; Houck and Cody, 2000; USDA Forest Service, 2001; Adams et al., 2006). Wildlife refers to all vertebrates (mammals, birds, reptiles, amphibians) and invertebrates (insects and other groups), except for pets, farm animals, fish, and diverse aquatic animals.

The urban environment, characterized by a concentration of buildings, roads, pollutants, noise, vehicles, and people, differs markedly from natural and agricultural lands. Not surprisingly, urban animals are equally distinctive (Stearns, 1967; Robinson, 1996). In general, urban vertebrates: (1) commonly use human-provided food sources; (2) readily switch diets; (3) may den or nest in artificial structures; (4) have relatively long breeding periods; (5) may occur in rather high density; (6) frequently move from location to location; (7) are habituated (accustomed to or behaviorally adjusted to humans); and (8) are generalists (Wheater, 1999; Adams et al., 2006).

1. There are no fixtures in nature.

2. The universe is fluid and volatile.

3. Ralph Waldo Emerson, Circles, 1841

1. Ye nymphs that reign o’er sewers and sinks,

2. The river Rhine, it is well known,

3. Doth wash your city of Cologne;

4. But tell me, nymphs, what power divine

5. Shall henceforth wash the river Rhine?

6. Samuel Taylor Coleridge, The City of Cologne, 1800

Virtually all cities began by a water body. After centuries or decades of expansion, today a city can claim lots of urban water bodies of many types. We now dive into six key topics: (1) urban wetlands and ponds; (2) constructed basins, ponds, wetlands, biofilters; (3) urban streams; (4) urban rivers; (5) flooding by river and stream; and (6) urban coastal zones.

Wetlands

The types and definitions of wetlands vary widely. We refer to wetlands as vegetation-covered areas where water is at or above the ground surface for an extended period most years (Keddy, 2000; Marsh, 2005; Mitsch and Gosselink, 2007). Such a water regime produces three major characteristics of wetlands:

1. Hydrology – water in sufficient quantity flows into and maintains the wetland.

2. Soil – wetland soil is often saturated, contains considerable organic matter, and mainly exhibits anaerobic decomposition.

3. Vegetation – plants adapted to wet soil predominate.

The nature of flows and movements

Imagine a walk in the city and suddenly reaching a spot where nothing moved. People, leaves, birds, air, water, vehicles, and clouds are absolutely still. Weird, even scary. Better stop and look sharp. Flows and movements around us are universal, never stop.

Processes in urban areas are in effect flows, movements and transport through space (Forman, 1999; Ball, 2009). Some are mainly vertical, including rainfall, evapo-transpiration, tree falls, and ecological succession. Horizontal flows, the focus here, generally cross heterogeneous space thus linking different land uses and habitats (Wegner and Merriam, 1979).

Preface

Most of us call urb our home. Today’s giant urban areas grow upward in population, with a fast-march outward. Now urban footprints, the agricultural and natural lands needed to sustain us, more than cover the globe. This great urban enterprise thoroughly interacts with ecology, reflecting a yet more powerful force. Nature molds our urban world, from “natural disasters” and resource scarcities to treasured plants and wildlife around us. Even pollutant and waste accumulation, green marketing, and natural landscapes pictured on our walls and in our dreams highlight the ecological dimension. The clashing and collaborating of these two giants – urb and ecology – lead to this book.

My lens focuses on spatial pattern, how it molds and responds to flows/movements, and how they all change. The pattern and process of mosaics, now a centerpiece of ecology from which most other components nicely follow, are central. Indeed, spatial pattern emerges as an especially useful handle for planners, engineers, landscape architects, park managers, pollution experts, architects, transportation specialists, hydrologists, and more. All can easily use the principles of urban ecology to build more-promising futures.

The essence of urban soil

Soil is the source of life. We build on soil, and nations rise and fall on their soil. Look closely and wondrous organisms appear, upon which we depend. In urban areas hard surfaces covering so much of the ground render much of the soil invisible. Consequently the remaining greenspaces and spots are that much more valuable for life and us. Most of the species central to urban ecology – trees and shrubs and flowers and wildlife and soil animals and soil microbes and us – depend on these remnant magical spaces.

Geologists, engineers, and land planners usually consider “soil” to be all the loose unconsolidated earth material (regolith) above the bedrock, thus focusing on the mineral component (Berke et al., 2006; Marsh, 2010). In contrast, most agriculturalists and soil scientists consider “soil” to be the upper portion of this unconsolidated material that is modified by the biological activity of abundant microbes, soil animals, and plant roots. Both perspectives are important in urban ecology.