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Humans value land for what it can provide: food, shelter, resources, and intrinsic beauty. There are also various classifications of land that are made for a variety of scientific and political purposes. However, human use of the land for these purposes can create problems that are prevented or addressed by regulations. In this module we will look at how human land use affects the environment and examine land use concepts and classification.

Learning Objectives

After reading this module, you should be able to

Agriculture, housing, recreation, industry, mining, and waste disposal are all land uses that benefit humans. But, as we have seen in previous chapters, these activities also have negative consequences. Extensive logging may lead to mudslides, and deforestation of large areas contributes to climate change and many other environmental problems. Change to the landscape is the single largest cause of species extinctions today. Paving over land surfaces reroutes water runoff, and these paved surfaces also absorb heat from the sun and reradiate it, creating urban “heat islands.” Overuse of farmland can lead to soil degradation and water pollution (FIGURE 29.1).

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Every human use of land alters it in some way. Furthermore, individual activities on any parcel of land can have wide-ranging effects on other land. For this reason, communities around the world use a number of methods, including laws, to influence or regulate both private and public land use.

As we saw at the beginning of this chapter, people do not always agree on land use and management priorities. Do we save a beautiful, ancient stand of trees, or do we harvest the trees in order to gain benefits in the form of jobs, profits, building materials, and economic development? Such conflicts can arise on both public and private land. To understand the issues involved in the use of land, we will look at three concepts: the tragedy of the commons, externalities, and maximum sustainable yield.

The Tragedy of the Commons

In certain societies, land was viewed as a common resource: Anyone could use land for foraging, growing crops, felling trees, hunting, or mining. But as populations increased, such common lands tended to become degraded—overgrazed, overharvested, and deforested. In 1968, ecologist Garrett Hardin brought the issue of overuse of common resources to the attention of the broader scientific community when he described the tragedy of the commons: the tendency of a shared, limited resource to become depleted because people act from self-interest for short-term gain. Hardin observed that when many individuals share a common resource without agreement on or regulation of its use, it is likely to become overused very quickly.

For example, imagine a communal pasture on which many farmers graze their sheep, like the one shown in FIGURE 29.2. At first, no single farmer appears to have too many sheep. But because an individual farmer gains from raising as many sheep as possible, each farmer may be tempted to add sheep to the pasture. However, if the total number of sheep owned by all the farmers continues to grow, the number of sheep will soon exceed the carrying capacity of the land. The sheep will overgraze the common pasture to the point at which plants will not have a chance to recover. The common land will be degraded and the sheep will no longer have an adequate source of nourishment. Over a longer period, the entire community will suffer. When the farmers make decisions that benefit only their own short-term gain and do not consider the common good, everybody loses.

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The tragedy of the commons applies not only to agriculture, but to any publicly available resource that is not regulated, including land, air, and water. For example, the use of global fisheries as commons has led to the overexploitation and rapid decline of many commercially harvested fish species, and has upset the balance of entire marine ecosystems.

Externalities

The tragedy of the commons is the result of an economic phenomenon called a negative externality. More generally, an externality is a cost or benefit of a good or service that is not included in the purchase price of that good or service. For example, if a bakery moves into the building next to you and you wake up every morning to the delicious smell of freshly baked bread, you are benefiting from a positive externality. On the other hand, if the bakers arrive at three in the morning and make so much noise that they interrupt your sleep, making you less productive at your job later that day, you are suffering from a negative externality.

In environmental science, we are especially concerned with negative externalities because they so often lead to serious environmental damage for which no one is held legally or financially responsible. For example, if one farmer grazes too many sheep in a common pasture, his action will ultimately result in more total harm than total benefit. But, as long as the land continues to support grazing, the individual farmer will not have to pay for the harm he is causing; ultimately, this cost is externalized to the other farmers. If the farmer responsible for the extra sheep had to bear the cost of his overuse of the land, he would not graze the extra sheep on the commons; the cost of doing so would exceed the benefit. From this example, we can see that in order to calculate the true cost of using a resource, we must always include the externalized cost. In other words, we must account for any potential harm that comes from the use of that resource.

Some economists maintain that private ownership can prevent the tragedy of the commons. After all, a landowner is much less likely to overgraze his own land than he would common land. Regulation is another approach. For example, a local government could prevent overuse of a common pasture by passing an ordinance that permits only a certain number of sheep to graze there.

Challenging the idea that government regulation is necessary, the late Professor Elinor Ostrom (1933–2012) of Indiana University showed that many commonly held resources can be managed effectively at the community level or by user institutions. Ostrom’s work, for which she was awarded the 2009 Nobel Prize in Economics, has shown that self-regulation by resource users can prevent the tragedy of the commons.

Maximum Sustainable Yield

When we want to obtain the maximum amount of a resource, we need to know how much of a given plant or animal population can be harvested without harming the resource as a whole.

Imagine a situation in which deer hunting in a public forest is unregulated, with each hunter free to harvest as many deer as possible. As a result of unlimited hunting, the deer population could be depleted to the point of endangerment. This, in turn, would disrupt the functioning of the forest ecosystem. On the other hand, if hunting were prohibited entirely, the deer herd might grow so large that there would not be enough food in the forests and fields to support the herd. In extreme cases, such as that of the reindeer of St. Paul Island (see FIGURE 19.3 on page 199), the population could grow unchecked until it crashed due to starvation.

Some intermediate amount of hunting will leave enough adult deer to reproduce at a rate that will maintain the population, but not leave so many that there is too much competition for food. This intermediate harvest is called the maximum sustainable yield. Specifically, the maximum sustainable yield (MSY) of a renewable resource is the maximum amount that can be harvested without compromising the future availability of that resource. In other words, it is the maximum harvest that will be adequately replaced by population growth.

MSY varies case by case. A reasonable starting point is to assume that population growth is the fastest at about one-half the carrying capacity of the environment, as shown on the S-shaped curve in FIGURE 29.3.

Looking at the graph, we can see that at a small population size, the growth curve is shallow and growth is relatively slow. As the population increases in size, the slope of the curve is steeper, indicating a faster growth rate. As the population size approaches the carrying capacity, the growth rate slows. The MSY is the amount of harvest that keeps the resource population at about one-half the carrying capacity of the environment.

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Forest trees, like animal populations, have a maximum sustainable yield. Loggers may remove a particular percentage of the trees at a site in order to allow a certain amount of light to penetrate to the forest floor and reach younger trees. If they cut too many trees, however, an excess of sunlight will penetrate and dry the forest soil. This drying may create conditions inhospitable to tree germination and growth, thus inhibiting adequate regeneration of the forest.

In theory, harvesting the maximum sustainable yield should permit an indefinite use without depletion of the resource. In reality, though, it is very difficult to calculate MSY with certainty because in a natural ecosystem, it is difficult to obtain necessary information such as birth rates, death rates, and the carrying capacity of the system. Once an MSY calculation is made, we cannot know if a yield is truly sustainable until months or years later when we can evaluate the effect of the harvest on reproduction. By that time, if the harvest rate has been too great, it is too late to prevent harm to the population.

All countries have public lands, which they manage for a variety of purposes, including environmental protection. The 2003 United Nations List of Protected Areas—the most recent global study of protected areas—includes almost 1.7 billion hectares (4.2 billion acres) of land in a variety of categories. Given that Earth’s total land area is about 15 billion hectares (37 billion acres), this means that approximately 11 percent, or one-ninth, of the land area of Earth is protected in one way or another. These areas, as well as protected marine areas, are shown on the map in FIGURE 29.4. Let’s look at both international and national categories of land protection.

International Categories of Public Lands

The 2003 United Nations List of Protected Areas classifies protected public lands into six categories according to how they are used: national parks, managed resource protected areas, habitat/species management areas, strict nature reserves and wilderness areas, protected landscapes and seascapes, and national monuments.

National Parks

There are roughly 3,400 national parks in the world, covering more than 400 million hectares (1 billion acres). This means that national parks make up about 2.7 percent of Earth’s land area. National parks are managed for scientific, educational, and recreational use, and sometimes for their beauty or unique landforms. In most cases, they are not used for the extraction of resources such as timber or ore. Some of the most famous national parks in the world are found in Africa and include Amboseli National Park in Kenya and Kruger National Park in South Africa. Parks like these generally exist to protect animal species such as elephants, rhinoceroses, and lions, as well as areas of great natural beauty. They also generate tourism, which can provide much revenue. On the negative side, in order to create and maintain national parks, governments have sometimes evicted and excluded indigenous human populations from the land. For example, in the winter of 2009, a new round of evictions from the Mau Forest in the Rift Valley of Kenya led to the displacement of 20,000 families. A Kenyan parliamentary report estimated that thousands of the evictees had not been resettled by 2012. Such programs continue to generate controversy in Kenya and other countries.

Managed Resource Protected Areas

This classification allows for the sustained use of biological, mineral, and recreational resources. In most countries, these areas are managed for multiple uses. There are approximately 4,100 such sites in the world, encompassing more than 440 million hectares (1.1 billion acres). In the United States, national forests are one example of this kind of area.

Habitat/Species Management Areas

These areas are actively managed to maintain biological communities, for example through provision of fire prevention or predator control. There are approximately 27,600 such sites, covering more than 300 million hectares (740 million acres). Karelia, in Northwest Russia and bordering areas of Finland, has one of the highest proportions of protected areas in Europe: 5 percent of its total area. Of this total, more than one-half consists of habitat or species management areas that are actively managed for hunting and conservation.

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Strict Nature Reserves and Wilderness Areas

These areas are established to protect species and ecosystems. There are approximately 6,000 such sites worldwide, covering more than 200 million hectares (490 million acres). The Chang Tang Reserve on the Tibetan Plateau in China was set aside to protect a number of species—including the declining population of wild yak—from hunting, habitat destruction, and hybridization with domesticated animals.

Protected Landscapes and Seascapes

These areas combine the nondestructive use of natural resources with opportunities for tourism and recreation. Orchards, villages, beaches, and other such areas make up the 6,500 such sites worldwide, which cover more than 100 million hectares (250 million acres). Among these protected areas is the Batanes Protected Landscape and Seascape in the northernmost islands of the Philippines, home to several endemic plant and animal species as well as important marine habitats.

National Monuments

National monuments are set aside to protect unique sites of special natural or cultural interest. There are almost 20,000 national monuments and landmarks in the world, covering nearly 28 million hectares (69 million acres). Most of these are established to protect historical landmarks, such as the Arc de Triomphe in Paris, France.

Public Lands in the United States

In the United States, publicly held land may be owned by federal, state, or local governments. Of the nation’s land area, 42 percent is publicly held—a larger percentage than in any other nation. As you can see in FIGURE 29.5, the federal government is by far the largest single landowner in the United States: It owns 240 million hectares (600 million acres), or roughly 25 percent of the country. Most of this land—55 percent—is in the 11 western continental states, and an additional 37 percent is in Alaska. Less than 10 percent of federal land is located in the Midwest and on the East Coast.

Public Land Classifications

Public lands in the United States include rangelands, national forests, national parks, national wildlife refuges, and wilderness areas. Since the founding of the nation, many different individuals and groups have expressed interest in using these public lands. However, most environmental policies, laws, and management plans have been based, at least partially, on the resource conservation ethic, which calls for policy makers to consider the resource or monetary value of nature. The resource conservation ethic states that people should maximize resource use based on the greatest good for everyone. In conservation and land use terms, it has meant that areas are preserved and managed for economic, scientific, recreational, and aesthetic purposes.

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Of course, many of these purposes are in conflict. In order to manage competing interests, the U.S. government has, for decades, adopted the principle of multiple use in managing its public resources. Some public lands are in fact classified as multiple-use lands, and may be used for recreation, grazing, timber harvesting, and mineral extraction. Others are designated as protected lands in order to maintain a watershed, preserve wildlife and fish populations, or maintain sites of scenic, scientific, and historical value.

Land Use and Federal Agencies

As shown in FIGURE 29.6, land in the United States, both public and private, is used for many purposes. These uses can be divided into a number of categories. The probable use of public land determines how it is classified and which federal agency will manage it. More than 95 percent of all federal lands are managed by four federal agencies: the Bureau of Land Management (BLM), the United States Forest Service (USFS), the National Park Service (NPS), and the Fish and Wildlife Service (FWS). BLM, USFS, and NPS lands are typically classified as multiple-use lands because most, and sometimes all, public uses are allowed on them.

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Although individual tracts may differ, the following are typical divisions of public land uses: