Additional Case Studies

GIS Essay
Too many geese?
Where have all the Songbirds gone?
Yanesha Forest
Snow Geese Threaten Artic Tundra

GIS Essay

GIS is an acronym you may hear with increasing frequency in the coming years. What does it mean, and why are people talking about it? At its most basic, a geographic information system (GIS) is a computer mapping system. This means that a GIS includes software that organizes spatial information, such as addresses, types of vegetation in different places, or the shapes of rivers and lakes, as well as the information itself--the data. In order for users--you and me--to understand all this spatial data, a GIS also needs to display or print the spatial information. Often a map on a computer screen is the main display method. On the computer screen you can zoom in and out to see details or overviews in different places; you can also add and subtract layers, to show different information about an area. Other times a printed map, which can be folded, carried around, and used anywhere, is the main product of a GIS.

A map of caribou calving areas in the Arctic National Wildlife Refuge, created using a GIS

(source: Ian Thomas, www.peer.org/maps.html)

Image6 (58.0K)

GISs serve many purposes. Most of the road maps you use today have been created with a GIS that makes map production and updating relatively easy and efficient. Every year your state's department of transportation, for example, may need to add new roads to its road maps. Your town's planning office needs to update zoning maps, and the tax assessor needs to maintain records of land ownership and land values and land uses. By creating computer maps, the data (new roads or land uses) can be corrected and reprinted relatively quickly. Without a GIS, maps would need to be updated by hand, using air photos and cameras. GISs are also used by utility companies. The companies that maintain your water system and your electric and phone lines may use a GIS to keep track of where the lines go, what their capacity and usage is, and where repairs are needed. Utility workers checking the lines may have computers in their trucks, or even hand-held computers, that let them access enormous databases of spatial information as they work, no matter where they are.

There are many applications of GIS in research and in spatial analysis, too. Suppose you knew the locations of 500 bald eagle nests, and you wanted to know how many of them were near highways that might pose risks to fledgeling eagles. Without a GIS you could visit all the sites and measure the distance from roads to each nest, but it might take a long time to visit that many sites. With a GIS you could overlay the two data sets and ask the computer to instantly calculate the number of nests within 50 or 100 meters of any road. At the same time you could calculate the proximity of nests to each other or to other key resources, such as lakes or streams where eagles could find fish. Add in a data file identifying elevations, and you could find out whether eagles tend to like south-facing slopes, or whether they avoid high-elevation locations.

An infinite number of questions and applications can be explored with a GIS. The main limitation is usually time and money. Often high-quality spatial data are time-consuming and costly to gather. Agencies or companies that produce data--and software--are often happy to sell their products, but sometimes the price is high. Often available spatial data are too coarse, or have too little precise and accurate detail, for questions a user wants to ask. The computers needed to run the complicated software may be expensive, too.

Fortunately, the U.S. government and many states and cities have invested heavily in GIS data, and since these data are created with taxpayer money, they are often available at low cost or even free--especially if you acquire them from the Internet. To get a sense of some of the geographic data currently available, look at the USGS's EROS data center web site (http://edc.usgs.gov) or at the Minnesota Department of Natural Resources "data deli" (http://deli.dnr.state.mn.us). Note that you won't be able to actually use any of the data unless you have the right GIS software and know how to use it. If you choose to learn a GIS, though, the opportunities and resources available are only going to grow in the coming years.

http://edc.usgs.gov/webglis/

Too Many Geese

Rising and then settling again in swirling clouds of glittering white, millions of snow geese move from field to field every winter, gleaning rice and other grain along the Gulf Coast of Texas and Louisiana (fig. 13.1). While these vast flocks delight hunters and bird watchers, they spell trouble for their summer nesting grounds along Canada's arctic coast (fig. 13.2). Beautiful snow-white birds with black wing-tips and pink bills and feet (a dark variant called the blue goose, has a blue-gray body and white head), snow goose populations have exploded over the past 30 years, especially those that follow the mid-continent flyway along the Mississippi River in their annual north and south migration. In the 1960s, the mid-continent population of "light" geese-a collective term for lesser snow geese and a smaller relative known as Ross' goose-was estimated to be around 800,000. Three decades later, that number had grown to between 5 and 10 million birds.

Biologists believe the rapid spread of soybean and rice farming in gulf coast wintering grounds is a large part of the explosive growth of snow goose populations. Millions of hectares that once were coastal marshes are now farm fields where mechanical harvesting leaves a bounty of grain on the ground. After a few months of feasting on this banquet, the geese are fat and healthy as they begin their annual spring migration north. Wildlife refuges and restored prairie potholes along migration routes provide safe places for the geese to rest and feed. And conversion of pastures to corn, barley, oats, rye, and wheat in northern states and provinces offers a valuable source of high-energy food during the migration. As a result, natural mortality has decreased and the population has climbed 5 to 7 percent per year for several decades.

This huge number of birds is having a devastating effect on the fragile tundra ecosystem in the far north where they breed and raise their young. Snow geese feed by grubbing, or pulling up and devouring plant roots. When the mid-continent population was less than a million birds spread out along the vast coastline from Hudson Bay to the Northwest Territories, plant-life on the salt marshes where they feed could keep up with summer goose grazing. But as their numbers grew, the birds began to eat more than could be replenished during the brief arctic growing season. Now, where the cord grasses and sedges preferred by geese once flourished, the ground is bare, salt-encrusted, and pitted with holes. Biologists question whether the feeding grounds will ever recover, because without plants to remove salt, the soil has become too saline for seeds to germinate.

A 1996 survey of 2000 km (1250 mi) of snow goose nesting area along the west coast of Hudson Bay estimated that 35 percent of the habitat was destroyed, another 30 percent was severely damaged, and the remaining 35 percent was seriously overgrazed. At least 30 other bird species dependent on the same habitat already have been adversely affected, including semipalmated sandpipers, red-necked phalaropes, dowitchers, Hudsonian godwits, wimbrels, stilt sandpipers, yellow rails, American wigeons, northern shovelers, oldsquaws, red-breasted mergansers, parasitic jaegers, and Lapland longspurs.

What can be done about this situation? One option would be to just wait for nature to take its course. Eventually, the geese will starve to death and their numbers will fall. But in the meantime, habitat will continue to degrade and many other species, some already rare, could suffer irreparably. Both Canadian and American wildlife services have taken steps to reduce the burgeoning goose population, including harassment to prevent nesting and "egging," or destruction of eggs. The nesting grounds are so spread out and difficult to access, however, that these activities aren't very effective. Hunting seasons have been expanded-including a spring season for northern states-and other rule changes such as reduced bag limits, use of electronic calls, more shells in each shotgun, and perhaps even hunting over bait have been proposed. It is hoped that the annual harvest of mid-continent light geese might be doubled or tripled with a goal of reducing the population to a sustainable level of about 1.5 million birds in a few years. Taking 2.5 million birds per year would represent a 25 percent annual harvest, up from the current level of about 8 percent. Increasing the "take" will be difficult, however, because snow geese are smart birds and notoriously hard to hunt.

This case illustrates several important issues of wildlife and biodiversity. Humans have changed the environment in ways that make some species overabundant while others have decreased or been driven into extinction. Whole ecosystems, even entire biomes, can be affected. In some cases the results are plain to see; in others they occur over such a wide area or in such remote places that we are unaware of what we have done until it is too late. In this chapter, we will look at some important types of biodiversity, how human actions disturb it, and ways we can protect and restore wild species and ecosystems on which we all rely.

Every June, some 2200 amateur ornithologists and bird watchers across the United States and Canada join in an annual bird count called the Breeding Bird Survey. Organized in 1966 by the U.S. Fish and Wildlife Service to follow bird population changes, this survey has discovered some shocking trends. While birds such as robins, starlings, and blackbirds that prosper around humans have increased their number and distribution over the past thirty years, many of our most colorful and melodious forest birds have declined severely. The greatest decreases have been among the true songbirds such as thrushes, orioles, tanagers, catbirds, vireos, buntings, and warblers. These long-distance migrants nest in northern forests but spend the winters in South or Central America or in the Caribbean Islands. Scientists call them neotropical migrants.

In many areas of the eastern United States and Canada, three-quarters or more of the neotropical migrants have declined significantly since the survey was started. Some that once were common have become locally extinct. Grover Archbold Park and Rock Creek Park in Washington, DC, for instance, lost 75 percent of their songbird population and 90 percent of their long-distance migrant species in just twenty years. Nationwide, cerulean warblers, American redstarts, and ovenbirds declined about 50 percent in the single decade of the 1970s. Studies of radar images from National Weather Service stations in Texas and Louisiana suggest that only about half as many birds fly across the Gulf of Mexico each spring now compared to the 1960s. This could mean a loss of about half a billion birds in total.

What causes these devastating losses? Destruction of critical winter habitat is clearly a major issue. Birds often are much more densely crowded in the limited areas available to them during the winter than they are on their summer range. Unfortunately, forests throughout Latin America are being felled at an appalling rate. Central America, for instance, is losing about 1.4 million hectares (2 percent of its forests or an area about the size of Yellowstone National Park) each year. If this trend continues, there will be essentially no intact forest left in much of the region in fifty years.

But loss of tropical forests is not the only threat. Recent studies show that fragmentation of breeding habitat and nesting failures in the United States and Canada may be just as big a problem for woodland songbirds. Many of the most threatened species are adapted to deep woods and need an area of 10 hectares (24.7 acres) or more per pair to breed and raise their young. As our woodlands are broken up by roads, housing developments, and shopping centers, it becomes more and more difficult for these highly specialized birds to find enough contiguous woods to nest successfully.

Predation and nest parasitism also present a growing threat to many bird species. While birds have probably always lost eggs and nestlings to predators, there has been a startling increase in predation in the past thirty years. Raccoons, opossums, crows, bluejays, squirrels, and house cats thrive in human-dominated landscapes. They are protected from larger predators like wolves or owls and find abundant supplies of food and places to hide. Their numbers have increased dramatically, as have their raids on bird nests. A comparison of predation rates in the Great Smoky Mountain National Park and in small rural and suburban woodlands shows how devastating predators can be. In a 1000-hectare study area of mature, unbroken forest in the national park, only one songbird nest in fifty was raided by predators. By contrast, in plots of 10 hectares or less near cities, up to 90 percent of the nests were raided.

Nest parasitism by brown-headed cowbirds is one of the worst threats for woodland songbirds. Originally called buffalo birds, these small blackbirds were adapted to follow migratory bison herds picking up seeds and insects from the droppings. Because they didn't stay in one place long enough to raise a family, they developed the habit of depositing their eggs in the nests of other species, leaving their young to be raised by surrogate parents. The young cowbirds are generally larger and more aggressive than the resident chicks, which generally starve to death because they don't get enough food. Adult cowbirds also find a welcome source of food and shelter around humans. Once fairly uncommon in the United States, there are now about 150 million of these parasites.

A study in southern Wisconsin found that 80 percent of the nests of woodland species were raided by predators and that three-quarters of those that survived were invaded by cowbirds. Another study in the Shawnee National Forest in southern Illinois found that 80 percent of the scarlet tanager nests contained cowbird eggs and that 90 percent of the wood thrush nests were taken over by these parasites. The sobering conclusion of this latter study is that there probably is no longer any place in Illinois where scarlet tanagers and wood thrushes can breed successfully.

What can we do about this situation? First, we can support sustainable development in Third World countries so that people there can enjoy a better standard of living without destroying their forests and natural areas. A number of such projects are discussed elsewhere in this book. Next, we should identify and protect critical habitat at home and abroad on which especially endangered species depend. Buying up inholdings that fragment the forest and preserving corridors that tie together important areas will help. In areas where people already live, we could encourage clustering of houses to protect as much woods as possible. We also might discourage clearing underbrush and trees from yards and parks to leave shelter for the birds.

Could we reduce the number of predators or limit their access to critical breeding areas? Human residents might not like the idea of reintroducing wolves and bears, but they might accept fencing or trapping of small predators. A campaign to keep house cats inside during the breeding season would certainly help.

Some wildlife managers already are trapping cowbirds. The Kirtland's warbler is one of the rarest songbirds in the United States. It nests only in young, fire-maintained jackpine forests in Michigan. Controlled burning to maintain habitat for this endangered species was started in the 1960s, but the population continued to decline. Studies showed that 90 percent of the nests were being parasitized by cowbirds. Since 1972, refuge managers have trapped and killed some 7000 cowbirds each year to protect the warblers. In the past two decades, the number of breeding pairs of warblers has risen from about 150 to nearly 400. Would it be possible to do something similar on a nationwide scale? Could we trap and kill 150 million cowbirds? Should we eliminate one species to save another? What do you think?

Yanesha Forestry in Peru

In the 1970s, Peru requested assistance from the U.S. Agency for International Development (USAID) for agricultural development of the Placazu Valley in the Peruvian Amazon. United States law required an environmental assessment of the project before any aid was made available. A multidisciplinary assessment team warned that the usual pattern of rural development with road building, forest clearing, and colonization by landless peasants from elsewhere in Peru would likely fail because high rainfall (about 7 m, or 275 in, per year) and infertile soil makes the valley unsuitable for farming. Furthermore, an invasion by outsiders would be disastrous for indigenous Arawakan Indian forest dwellers. Instead, the consultants suggested, a locally-run sustainable forestry project could provide long-term economic development, protect biodiversity, and preserve native culture.

One of the first changes needed for this forestry project was recognition of land ownership by native communities in the Palcazu Valley. This was necessary because Indians in Peru typically do not hold title to traditional communal lands. Ater several years of technical assistance, community education, and political advocacy, land claims of eleven native communities were recognized legally, and an Indian forestry cooperative--the first in South America---was established. Called COFYAL (the Spanish acronym) or the Yanesha Project (after the native people's name for themselves), the cooperative included five native communities and about 70 individual Arawakan Indians.

Rather than clear-cut the forest in large blocks, the Yanesha Project is based on strip-cutting. Narrow strips---30 or 40 m wide--- are cut through the forest. Oxen drag out logs, resulting in less damage to soil and remaining trees than would be caused by tractors or bulldozers. Strips are never burned or cultivated and are only about twice as wide as the average tree-fall gaps, so natural regeneration is raid. The strips quickly fill with a wide diversity of trees re-sprouting from stumps or from seeds drooped by nearby trees. Wildlife is disturbed very little by the narrow strips.

COFYAL technicians identify forest suitable for harvesting and locate hauling roads based on tree types, slope, and proximity to streams, wetlands, and other protected areas. Strips are harvested in an alternating pattern (1,3,5, then 2,4,6, for example) so that it takes six to ten years to complete a cycle and about 30 to 40 years between harvesting on any particular strip. Rather than cut only the biggest trees, which fall on and crush smaller trees, as is done in many tropical timber operations, the Yanesha foresters first cut and remove pole-size stems and then proceed to remove the larger trees.

Everything from the forest is used. A portable sawmill produces lumber from larger timbers, a hydraulic sysem preserves posts and poles, and scraps are converted to charcoal for cooking and heating. Because lumber is marketed locally, a wider range of species is sold than would be acceptable in national or international markets.

So far, the project seems to be meeting its goals admirably (1) to employ members of the native communities, (2) to manage natural forests for sustained yield and a natural species mix, and (3) to protect the culture of the Yanesha people while still allowing economic development. By taking forest ecology into account, and managing resources according to local conditions and needs, the COFYAL project is incorporating many principles of ecosystem management and

Snow Goose Population Threatens Arctic Tundra Habitat

May, 1999

As spring returns to Canada, natural resource managers are bracing for the arrival of one species that has prospered extremely well in recent years: the lesser snow goose. Migrating from southern states by the thousand, these geese return to nest in the Canadian arctic every summer. Beautiful snow-white birds, or sometimes blue-grey, snow geese are becoming a problem because they are overpopulating their summer range. The delicate tundra vegetation is being over-grazed, and other species are losing nesting territory as the snow goose population grows. The greatest damage has been observed so far in the eastern arctic and the west coast of Hudson Bay.

Lesser snow geese are flourishing because they are very lucky in their winter habitat. They spend a long fall migration period and the winter in the southern United States, where rice has become a widespread crop in recent years. Flooded winter rice fields, still holding plenty of scattered rice grains and other vegetation, provide an ideal food source for the migratory snow geese. When spring comes the geese are fat and healthy, with fewer than normal winter fatalities. As a consequence, breeding populations in the spring of 1999 were over 5 million, three times the population just 30 years ago.

There are three species of mostly-white geese. Lesser snow geese and Ross' geese are smaller and are the main source of tundra destruction, especially in Canada's central and eastern Arctic and sub-Arctic (see map). Greater snow geese look similar to lesser snow geese except for their size, and they tend to travel and nest along the coasts of North America. In addition to their growing numbers, lesser snow geese are considered the greatest risk to tundra habitat because they are more aggressive than other species in grubbing out the roots of plants, as well as grazing the shoots, as vegetation becomes scarce.

In response to the growing numbers, wildlife managers have established unusually lenient hunting rules in many states where the geese winter, including such measures as eliminating bag limits, extending hunting seasons, and lengthening hunting hours. It remains to be seen how successful these steps will be, since snow geese are generally more wary and difficult to shoot than other species of waterfowl.

For more information, see these related web sites:

Images of degradation: vegetation destruction by grubbing snow geese, from the Hudson Bay Project

Snow geese: information from the U.S. Fish and Wildlife Service

Further information from the U.S. Fish and Wildlife Service

Species and distribution information

To read more, see

Environmental Science, a Global Concern, Cunningham and Saigo, 5th ed.
Population dynamics and carrying capacity: p. 121-124
Density-dependent factors in population regulation: p. 128-130
Tundra: p. 97

Environmental Science, Enger and Smith, 6th ed.
Dundra: pl. 84-85
Latitude effects on biomes: p. 85-86
Population principles: p. 99
Carrying capacity: p. 99