The New Neotropical Companion

ISBN-13: 9780691115252

Media Type: Paperback

Publisher: Princeton University Press

Publication Date: 03-07-2017

Pages: 448

Product Dimensions: 7.60(w) x 9.50(h) x 1.10(d)

John Kricher is professor of biology at Wheaton College. His many books include Tropical Ecology, The Balance of Nature: Ecology's Enduring Myth, and Galápagos: A Natural History (all Princeton).

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The New Neotropical Companion

PRINCETON UNIVERSITY PRESS

Welcome to the Torrid Zone

Into the Torrid Zone

The lure of the tropics, the desire to visit a land of relentless heat and humidity, of scorching sun and torrential rain, may at first seem a bit hard to explain (plate 1-1). But it's not. It can be explained in one image: plate 1-2.

Seeing a Jaguar (Panthera onca) for the first time, in its element, its home, its piece of rain forest, is worth any long bumpy and dusty ride, a few annoying mosquitos, muddy boots, an airport delay, or any other minor inconvenience typical of modern travel. Observing a real live Jaguar in the wild provides a remarkable connectivity with Earth's natural world that is simply unrivaled. You have really seen something special. And there is so much more. The majesty of myriad imposing tall rain forest trees and the chance of encountering some of the multitudes of creatures that dwell within those forests is an experience that is nothing short of precious (plate 1-3). The tropics, a land of heat and humidity historically termed the Torrid Zone, contains most of the world's species of, well, pretty much everything: plants, birds, mammals, reptiles, insects, you name it. And that is what this book is about. We are going to visit the Neotropics. Let's begin with some geographical perspective.

Beginning about 248 million years ago, just after the end of the Permian period and the Paleozoic era, the world's continents began drifting apart, a process that continues today. This separation is the result of a dynamic geological process known as plate tectonics. Continents made primarily of granite ride passively atop large and slowly moving plates of basalt (which compose the earth's crust) kept in motion by the convective heat of the planet itself. The result, in a nutshell, has been that widely separated continents now contain markedly different groups of organisms. That is because 248 million years allow for a lot of evolutionary change, for new species to diverge and evolve, for whole new groups of organisms to develop. For example, the primates of the New World tropics (the Neotropics), the monkeys, marmosets, and tamarins of Middle and South America, are distinctly different from the Old World monkeys and apes, though they all (along with us), of course, ultimately share common ancestry in the order Primates (plate 1-4).

Hornbills, large birds with colorful, elongate, bananalike bills, are found only in Africa and Asia. However, an anatomically similar but only distantly related group of birds, the toucans, toucanets, and aracaris (plate 1-5; discussed in chapter 8), is found only in the American tropics. Through these and numerous other examples, biogeographers have identified well-separated geographic realms comprising largely distinct floras and faunas.

North America is in the Nearctic biogeographic realm, which is primarily temperate in climate. Europe and northern Asia are in the Palearctic realm and are likewise mostly temperate. The African realm and Australasian realms (including islands such as Borneo and New Guinea) are largely tropical in climate, though with large areas of hot desert. The realm known as the Neotropics begins in central Mexico, extends through the Caribbean region, and reaches to the tip of South America. Although temperate at both its northern and southern extremes, the realm of the Neotropics is largely tropical. Here's why.

The bulk of the Neotropic land area lies between the Tropic of Cancer to the north and the Tropic of Capricorn to the south, with the equator in the middle. The names Cancer and Capricorn refer, of course, to constellations of the zodiac through which the sun appears to trace its annual course. Because Earth is tilted on its axis, by 23.44°, it is a seasonal planet, its north side facing the sun part of the year (the northern summer months) and its south side facing the sun part of the year (the northern winter months). Thus on the dates of the summer and winter solstices the sun is either 23°26'22" (about 23.44°) north (directly over the Tropic of Cancer) or 23°26'22" south (directly over the Tropic of Capricorn). For those of us at northern latitudes, the sun appears low in the sky in winter and high, virtually overhead, in summer. On the dates of the equinoxes heralding the official beginning of spring and, six months later, autumn, the sun sits directly over the equator.

It is thus obvious that the part of Earth receiving the most solar radiation (i.e., direct sunlight) within the course of a year is the region lying between the Tropics of Cancer and Capricorn, a 46.88° belt that essentially defines what we call the tropics. The fact that the sun is never more than 23.44° north or south of the equator is the major reason the tropics exist. Earth receives different amounts of solar radiation depending upon latitude. But if you are in the Torrid Zone, no matter where on Earth, you get a lot of direct sunlight throughout the year and thus, unless you are at a high elevation, you experience a lot of heat. It is therefore consistently warm in the lowland tropics (plate 1-6).

North of the Tropic of Cancer and south of the Tropic of Capricorn you enter the temperate zone, an area of more extreme annual climate variability. North of the Arctic Circle (66°33'39" N) you enter the northern polar zone, historically termed the Frigid Zone, a region of extreme climatic stress that supports an ecosystem called tundra, realm of musk oxen and polar bears. The same, of course, is true climatically when you cross the Antarctic Circle (66°33'39" S) and enter the southern polar zone, the land of vast ice and diverse penguins.

Immediately beyond the Torrid Zone latitudes you move into the subtropics (plate 1-7). It is not unusual for parts of Florida to experience winter frosts, but nonetheless the southern areas of Florida, including Everglades National Park, are ecologically subtropical. Species of typically tropical plants such as mangroves and the Gumbo Limbo tree (Bursera simaruba) are found here. Many physical characteristics of typical tropical forests (such as the presence of high levels of epiphytic plants and buttressed roots) are evident to various degrees in coastal forests as far north as the Georgia–South Carolina border (plates 1-8–9). This is because the warm oceanic currents of the Gulf Stream (discussed below) allow the coastal Southeast to remain relatively balmy throughout the year, extending the subtropics northward (plate 1-10).

But Where, Exactly, Are the Neotropics?

Because of the mild climate provided by the warm and complex current known as the Gulf Stream, the Caribbean islands all are part of the Neotropical realm, even though some (such as the Bahamas and Bermuda) are outside of the Torrid Zone. Therefore, the islands of the Bahamas, the Greater and Lesser Antilles, the West Indies, and so forth, are all in the Neotropics. So if you have taken a trip to Abaco, Jamaica, Puerto Rico, Martinique, or Cuba, you have visited a Neotropical place.

Much of northern and western Mexico is either subtropical or temperate (because of the influence of mountain ranges) in climate, but the lowland eastern slope of Mexico adjacent to the warm Caribbean Sea (Veracruz, for example) is warm and humid. Indeed, it is in this region that you find the most northerly extension of Neotropical evergreen moist forests. The remainder of Middle America, Belize, Guatemala, Costa Rica, Nicaragua, Honduras, El Salvador, and Panama, is Neotropical, and each of these countries contains typical tropical ecosystems.

Finally, and perhaps most obviously, we come to South America. This huge continent contains the largest tract of remaining tropical rain forest in the world, the immense Amazon Basin. While the country of Brazil holds claim to most of Amazonia, all neighboring countries share part of it. Thus you can visit diverse tropical lowland evergreen forest not only Brazil but also in Bolivia, Peru, Ecuador, Colombia, Venezuela, Guyana, Suriname, French Guiana, Paraguay, and parts of northern Argentina.

Note that the southern regions of South America in Chile and Argentina are south of the Torrid Zone and have a temperate, seasonal climate.

It's Not All "Tropical" Even in the Torrid Zone

Imagine that you are exiting your hotel in Guayaquil, Ecuador, a sea-level port city, for a brief ride to the airport. You walk out from the air-conditioned lobby into hot and decidedly humid air. It's muggy and feels very "tropical." After a short and scenic flight, your aircraft touches down in Quito, about 267 km (166 mi) away, as the Andean Condor flies. You have left the sultry sea-level climate of Guayaquil for the clear Andean air of Quito, which is located at about 2,800 m (9,200 ft) above sea level. The climate feels decidedly temperate, cooler and drier. That's because it is.

Latitude alone does not determine the tropics. Elevation is also a critical variable. The youthful and dynamic Andes Mountains run the western length of South America, extending from Tierra del Fuego at the southern tip of the continent all the way north and east through Venezuela, ending in the gentle northern and central ranges of the island of Trinidad. The great European explorer Alexander von Humboldt (1769–1859) was the first to describe in detail how habitats change with elevation (plate 1-11). He is credited with having elucidated the concept that was later formalized and called the ecological life zone (detailed in chapter 2). Humboldt realized that climate characteristics change with elevation and that climate, as you might have surmised by now, is the most important variable in determining what sort of habitat or ecosystem will be present. Humboldt documented how a zone of lowland tropical forest (i.e., rain forest) gradually transitions into cloud forest with increasing elevation and how, above cloud forest, trees become increasingly stunted until a zone is reached called páramo, a cold and windswept ecosystem of tussock grass and dwarfed trees. Snow is common at this elevation. When it comes to ecological montane (i.e., mountainous) life zones, the latitude may be well within the Torrid Zone, but elevation makes all the difference. Indeed, if you have a strong enough arm you could stand on the equator high in the Andes and toss a snowball east into the hot and steaming jungles of Amazonia far below (plate 1-12).

So What Actually Are the Tropics?

The climate of the tropics will form the main topic of the next chapter, but for now, know this: a tropical climate is consistently warm but variably wet. Much of the area within the tropic zone is not rain forest. There are, for example, deserts in the tropics, including the desolate Atacama Desert of coastal Peru and Chile. The African Serengeti, which is a vast savanna of grassland and scattered trees, is famous for the forced annual migrations of herds of large animals such as wildebeest, which must move seasonally to find water. Much of central and southern Brazil is cerrado, an ecosystem ranging from dry forest to open grassland depending upon seasonal moisture input and occurrence of natural fire (chapter 14).

Therefore, a large part of the tropics experiences a seasonal climate in which the seasons vary between rainy and dry rather than hot and cold. Tropical areas have relatively little annual variability in air temperature (and the temperature is generally quite warm), but rainfall amounts may vary dramatically throughout the year, something to bear in mind when you plan a trip. Tropical ecologists speak of wet and dry seasons rather than winter (implying cold) and summer (implying heat). However, in many lowland rain forests rainfall is sufficiently abundant on a daily basis throughout the year that the dry season is scarcely expressed, and thus the forest remains constantly wet and lush year-round. This is true rain forest.

Most people who visit the Neotropics tend to seek a rain forest experience and thus should be prepared for heat, humidity, and a bit of rain, sometimes quite a bit of rain, often daily.

Welcome to the Jungle: A Quick Overview

Because of the relatively constant presence of heat, rain, and humidity, much of the Neotropics is biologically lush, profligate with species of plants and animals (plate 1-13). It is this profusion of diverse life that attracts so many ecologists as well as ecotourists to tropical destinations and has long fascinated explorers and naturalists, including Charles Darwin, Alfred Russel Wallace, and Theodore Roosevelt. Life-forms are not randomly distributed on Earth. Tropical terrestrial ecosystems occupy only about 7% of Earth's surface but are believed to hold more than 50% of the world's terrestrial plant and animal species. There is a very basic observation nested in this reality: tropical climate is conducive to supporting diverse life, more so than any other climate to be found on the planet. As climate becomes less warm, less moist, less equable, fewer species are to be found. The term biodiversity, referring generally to the sum total of species present in an area or region, has come into common usage over the past decades. Indeed, one of the principal concerns of ecologists is that the present century will see a severe reduction in global biodiversity, including many species of tropical organisms (chapter 18, and see "Conservation Issues," below).

The profusion of life in the tropics takes physical form in the concept of the rain forest biome once commonly referred to as "jungle." Tarzan, as most of us know, lived happily in the African jungle, moving easily from one place to another by swinging on vines while hollering loudly. As a child in the early 1950s I used to watch a television show titled Ramar of the Jungle, about a medical doctor facing heroic weekly situations as he plied his way through the jungles of Africa and India. It wasn't a great show but it did get me interested in the tropics. And one of my first really good introductions to tropical plants and animals was Ivan Sanderson's classic Book of Great Jungles (1965).

So what is a jungle? The term (derived from the Sanskrit word jangala) has always been associated with dense tropical forests and usually invokes visions of plant growth so prolific as to be virtually impenetrable. The mind's eye sees massive trees draped with thick vines, a mysterious and somewhat foreboding blanket of vegetation hosting a strange cacophony of birds and insects. But that vision is not entirely accurate, and rain forest and jungle do not mean quite the same thing.

It is true that there are many places in the tropics where the vegetation is so profuse as to require the skilled use of a tool such as a machete to move through it. But these are typically areas of relatively recent disturbance (chapter 7), such as cleared areas that then receive abundant sunlight that promotes rapid and prodigious plant growth. Where there is mature, old-growth rain forest the sense of impenetrability is much reduced. It is actually no more difficult to maneuver through rain forest than through most temperate-zone forest. Large trees are relatively widely spaced, and the lack of light at the ground surface (because of the dense leafy canopy above) prevents much in the way of plant growth that would impede movement along the forest floor.

Tropical rain forest is tall, lush, and most of all diverse with species. (It will be described in detail in chapter 3). It is without doubt the ecosystem that most visitors to the Neotropics seek to experience. Fortunately, there are still many places where that is easily possible.

Visiting the Neotropics

When A Neotropical Companion was first published (in 1989) there were relatively few well-known and reliable tourist facilities within the Neotropics. The famous Asa Wright Nature Centre on Trinidad was one of them. This one-of-a-kind guesthouse, now much expanded, offers easy access to lush forest abounding in tropical wildlife (about 2,200 plant species, 617 butterfly species, and 400 bird species) and has been visited by thousands of naturalists since the 1950s. It remains today one of the premier destinations in which to experience the Neotropics.

Since 1989 Neotropical ecotourism has burgeoned and, unsurprisingly, so has the availability of fine accommodations throughout the region. It is now possible to book a stay at any number of highly comfortable and commodious lodgings (far too many to list in this book) in virtually any Neotropical country, each of which generally offers a tasty (and safe) cuisine, hot showers, clean and comfortable rooms, and, most important, highly competent local guides. One example is the Canopy Tower, located in Soberania National Park, Panama, very near the Panama Canal and just a short drive from Panama City (plate 1-17). This unique facility, located high atop Semaphore Hill Road, is an old radar installation that has been completely renovated, upgraded, and converted to an ecotourism facility of the highest quality. It offers an outstanding rain forest experience that includes daily guided tours to such places as the famous Pipeline Road, one of the most important field sites in historic and ongoing studies of Neotropical ecology (and located very near Barro Colorado Island, one of the most important research stations in the Neotropics). As with most other lodges, it is easy to book reservations on the Internet for the Canopy Tower (and its sister facilities, the Canopy Lodge, Canopy Camp, and Canopy B&B, take your choice).

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Excerpted from The New Neotropical Companion by John Kricher. Copyright © 2017 Princeton University Press. Excerpted by permission of PRINCETON UNIVERSITY PRESS.
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Table of Contents

Preface 9

Acknowledgments 11

How to Use This Book 12

1 Welcome to the Torrid Zone 15

2 Why It Is Hot, Humid, and Rainy in the Tropics 29

3 Rain Forest: The Realm of the Plants 39

4 Finding Animals in Rain Forest 58

5 Sun Plus Rain Equals Rain Forest 73

6 Essential Dirt: Soils and Cycling 81

7 If a Tree Falls . . . Rain Forest Disturbance Dynamics 95

8 Evolutionary Cornucopia 113

9 Why Are There So Many Species? 134

10 Tropical Intimacy: Mutualism and Coevolution 155

11 Evolutionary Arms Races: More Coevolution, More Complexity 181

12 Cruising the Rivers to the Sea 205

13 Scaling the Andes 235

14 Don’t Miss the Savannas and Dry Forests 250

15 Neotropical Birds: The Bustling Crowd 262

16 From Monkeys to Tarantulas: Endless Eccentricities 319

17 Human Ecology in the Tropics 365

18 The Future of the Neotropics 377

Appendix Words of Caution: Be Sure to Read This 389

Further Reading 392

Index 417