Ch13

Chapter 13 - LANDSCAPES AND SEASCAPES

The Big Picture

The Earth's surface is partly land and mostly water. This chapter discusses the Earth's terrestrial ecosystems (landscapes) and marine ecosystems (seascapes), along with the forest and fishery resources they contain. The Earth's landscapes may be classified into many land use categories, including forested areas, pasture, agricultural land, deserts, wetlands, and urbanized areas. Within the world's forested lands, there are different forest types, including rainforests, dry forests, coniferous forests, deciduous forests, closed canopy forests, and open canopy forests. Forests are valued greatly by humans, as they are used for lumber, boat-building, and firewood. Forests also regulate climate, store water, prevent erosion, store carbon, provide wildlife habitat, and provide recreational opportunities, in addition to producing trees. These functions are important to humans, but are often not valued by humans to the same extent. Forests can be managed to maximize tree production, such as on a pine plantation, but if a forest is managed for only one function, other functions may be compromised. Losses of forest resources are occurring very rapidly worldwide. This is a cause for concern among many environmental groups and native peoples, because of the loss of these functions and values (see the Case Study on Clayoquot Sound Logging). Seascapes cover approximately 70 % of the Earth's surface. These ocean environments contain the greatest biodiversity on the planet in the form of coral reefs and deep-sea ecosystems. Seascapes encompass estuaries and upwelling systems that provide the greatest biological production on the planet, extensive food webs which support the world's fish harvest, and massive current systems that regulate our planet's climate. Thus, the environments covered in the chapter section on seascapes are some of the most important ecosystems in the world to humans and the Earth's biota. However, concerns have been raised that human harvests from the sea have reached the limits of sustainability. In addition, changes in landscapes (deforestation, increased run-off from agriculture and urban areas) are causing impacts in the coastal seas. Conservation of marine resources has become a priority among coastal human populations worldwide. Although landscapes and seascapes are very different environments, there are many common themes involved in conserving their biological resources and managing the human use of these ecosystems. These common themes will be explored in this chapter.

Frequently Asked Questions

What is an "old growth" forest?

This term means that the trees in the forest are very old and have never been cut in the last 250 years. Often, the trees are 1000 years old or more.
The term "ancient forest" or "virgin forest" is often used as an alternative.
These three names are not scientific terms, but are used in many well-publicized disputes about logging in forests in the Pacific Northwest of the USA.
The term second growth refers to a forest that has been cut and is regrowing.

How much forest land is there in the world?

According to data from the mid-1970's (See Table 13.1), there are 2.5 billion hectares of closed forest and 1.2 billion hectares of open woodland forest and savannas worldwide (1 hectare (ha) = 2.47 acres).
Africa has the greatest amount of open woodland and savanna (570 million ha or 48 % of the total), whereas the former USSR has the greatest closed canopy forest resources (785 million ha or 30 % of the total).
More recent data is not provided here, but you should check below under "Ecolinks on the Web" for more up-to-date, but perhaps less reliable, data sources.

How much forested land is left in the USA?

There are 340 million hectares of commercial-grade forests in the USA, with 75 % of them in the East (especially the pine plantations of the Southeast), and 25 % in California, Oregon, Washington, Montana, Idaho, Colorado, and Alaska.
Of the 340 million ha, 62 % of it is privately owned, 19 % is on US Forest Service land, and 19 % is on other federal lands.

What are the causes of deforestation?

There are two kinds of deforestation: direct and indirect.

Direct deforestation is caused by cutting trees for industrial forest products (paper and lumber), fuelwood (cooking and heating), and to clear land for agriculture (cattle ranching, palm oil plantations, tobacco farms). Direct deforestation occurs worldwide, but is occurring most rapidly in tropical South America, Asia, and Africa.

Indirect deforestation is due to air pollution by acid rain and ozone, which in combination with insects and parasites, kills the trees. Indirect deforestation is especially a problem in Europe.

How much rainforest is lost each year?

In truth, we don't know the exact amount lost each year, but we can estimate that loss from satellite imagery.

In the tropics, a forested area the size of Pennsylvania is probably lost each year, but this is uncertain. The rates of rainforest loss often quoted by environmentalists (two football fields or 1 hectare/second) are on the high side, because they are based on 1988 estimates made using remotely sensed Advanced Very High Resolution Radiometry satellite images. Such images, with a pixel resolution of 1 km x 1 km, can show smoke from slash and burn fires.
More recent deforestation estimates based on Landsat surveys are lower:

Using AVHRR satellite imagery- A 1988 study conducted showing the fires in the Brazilian Amazon region estimated that 8 million hectares were cut down between 1987-88, which amounted to 2.2 % of the rainforest lost in that one year (0.25 hectares/second). This year was a peak year for deforestation.

Using Landsat satellite imagery - But a recent study of the same region (David Skole and Compton Tucker, of the University of New Hampshire and NASA in Science, 25 Jun 1993) using over 200 Landsat images examined for areas actually cut down produced a lower estimate over a longer period of time:

Date

Area deforested based on Landsat imagery

1978

7.8 million hectares

1988

23.0 million hectares

Change from 1978-1988

15.2 million hectares

Thus, the 1978-1988 loss was 15.2 million hectares, or 1.52 million per year, much lower than the 8 million previously estimated. This is more like 0.05 hectares/second rather than 1 hectare/second. Prove it to yourself by dividing 1.52 million hectares by 365 days/year, 24 hr./day, 60 min/hr, and 60 seconds/min.

How are commercial forests currently managed?

There are two major types of management of forests: plantations and natural regrowth.

Plantations (tree farms) are managed for either maximum sustainable yield (MSY) of wood for lumber or a short rotation time for wood pulp for paper production with seedlings planted after a clear-cut, and fertilizer, pesticides, and herbicides added as needed, sometimes by helicopter (Fig. 13.9, early successional stage). These are typically even-aged stands, with all the trees the same age.

Natural regrowth management is less intensive than a plantation and allows trees to regrow from seeds deposited by neighboring adult trees that were left intact after selective cutting and natural succession is allowed to occur. These forests will have uneven-aged stands of trees, and some trees will be old and useful for making hardwood furniture (Fig 13.9, late successional stage).

What is clear-cutting and what does clear-cutting do to a forest ecosystem?

Clear-cutting is a practice in which all the trees in a stand, no matter what species, are cut down and harvested over large areas of forest, leaving behind stumps or unvegetated soil.
No trees are left to reseed or revegetate the land, which must be replanted by humans with seedlings.
Clearcutting increases soil erosion and runoff, causes nutrient cycling to be disrupted, increases nitrate levels and sedimentation in streams (Fig 13. 10).
Experimental tests of clear-cutting have been done in the U.S. Forest Service's Hubbard Brook experimental forest in New Hampshire and the H. J. Andrews experimental forest in Oregon.

When an entire watershed was clear-cut, and compared against a nearby watershed that was left forested, there were dramatic increases in soil erosion rates and stream sedimentation rates. At the Oregon forest, landslides occurred after clear-cutting.
In addition, water storage declined and nutrients were lost from the ecosystem. Nitrate rates in the watershed's central stream exceeded public health standards in the New Hampshire clear-cut forest.
The increased stream sedimentation, landslides, and water nutrient cause spawning of anadromous fishes like salmon to decrease. This is why fisherman are opposed to clear-cuts near salmon streams in the Pacific Northwest.

What are the alternatives to clear-cutting and what are their benefits and drawbacks?

The main advantage of clear-cutting to timber companies is the low cost to harvest the trees. There are several alternatives to clear-cutting, but all of these involve cutting fewer trees per unit area. Thus the major drawback of each alternative method is the increased cost of harvesting trees. The alternatives range from almost no cutting (selective cutting) to some that are similar to clear-cutting (seed tree cutting). Here they are in order of most desirable to least desirable alternatives to clear-cutting :

selective cutting - small groups of individually marked mature trees are cut and removed. The rest of the forest remains intact, and the forest can regenerate naturally. Benefits include a natural seed source, little or no soil erosion, and a minimal impact on wildlife habitat.

shelterwood cutting - in this method, all the mature trees are harvested over a period of time. In the first year, undesirable trees are removed. Afterward, new desirable tree seedlings become established. Then after a decade, many mature trees are removed. After another decade, the last mature trees are cut, but by this time there are many young trees regenerating. Benefits of this method include natural reseeding and low soil erosion, because some trees are always present.

strip cutting - In this method, long, wide swaths of forest are removed. This allows trees in the non-cut swath to reseed and protect the new seedlings from excessive sun and wind. It also provides wildlife habitat and an aesthetic barrier from the strip that has been cut. However, soil erosion can be high in cut strip.

seed-tree cutting - In this method, all the trees except for a few scattered mature trees are cut. The mature trees left behind produce seeds for regeneration. Benefit is seed production alone; the soil is largely exposed as in a clear-cut, so that erosion may be high.

What is meant by sustainable forestry?

The phrase "sustainable forestry" can mean different things and is used differently by different people. There are two definitions of sustainable forestry:

Sustainable timber harvests means that wood production may be sustained for an indefinite period of time under a maximum sustainable yield model on a tree plantation (see Chapter 12); however, other forest ecosystem functions may not be sustained under such a plan.

Sustainable forest harvest means that forest ecosystem functions are sustained for an indefinite period of time; these include carbon storage, soil erosion protection, climate regulation, water storage, wildlife habitat, and recreational opportunities for people.

Sustainability of forest functions has not been experimentally demonstrated, except when harvest rates are kept very low (coppicing, which is the selective removal of limbs from trees, and selective cutting, but not clear-cutting). It is quite possible that when a person says "sustainable forestry" they could be referring to either of these meanings.

Are currently used forest harvest practices sustainable?

During the past 100 years, forest harvest rates have been higher than rates of regrowth and recovery.
During the whole of human history, there has been a net loss of forested area worldwide and in the USA. Thus, the practice of forestry as it is practiced today is non-sustainable over the long-run.

What is "multiple use" of forest land?

In the USA, the Bureau of Land Management and the U. S. Forest Service have been charged by Congress with making multiple use of forests, not just using them for timber production (The Multi-Use Sustained Yield Act).
This means encouraging the use of forests for recreation (sight-seeing, birdwatching, camping, hunting, and fishing), as well as for conservation of wildlife habitat and water resources.
Thus, the National Forests and other government must be managed for several competing uses at the same time (including mining and grazing, which are often destructive practices).
It is impossible to manage the forests to maximize each of these uses, so trade-offs and less than maximal use must occur. Areas are managed so that some that are best for timber production are maximized for that use, whereas others that are best for another use, such as recreation, are minimized for timber production.
Overall, this approach achieves a balance of uses, but conflicts will occur in areas that are good for many uses.

How can parks and preserves protect landscapes?

Parks and preserves protect forest and other landscape ecosystem functions by preventing extractive use of the land. This approach has gained a great deal of favor in recent years among conservation biologists, using Island Biogeography Theory.

Parks provide people with recreational areas, protect biodiversity, provide water storage, provide wildlife habitat, and protect places of aesthetic value (Yosemite National Park is such a place).

Nature preserves are somewhat different than parks, in that they are solely established to protect nature or wilderness for its own sake, not for humans. In some parks and preserves, humans are not allowed (for example, Sengwa National Park in Zimbabwe) so that natural ecosystems can exist without human influence.

What is Island Biogeography Theory?

The concept of island biogeography and the underlying mathematical model was introduced in Chapters 7 and 12.
Parks and preserves are essentially "islands" surrounded by an altered landscape in much the same way that oceanic islands are surrounded by water. Thus, the principles of this mathematical theory can be applied to park and preserve "islands".
Generally the larger the island, the more species it will contain, and the closer the island is to a source of species the more species it will contain. The same is true for parks and preserves. If a park is large, this is generally thought to be better than a small area park, because it will contain more biodiversity.
However, several small parks of the same total area can often have as many species as one large park, with an advantage of guarding against catastrophic loss in one of the parks (Fig. 13.12).
Also, it is good to have a series of parks, or to have parks reside close to large areas of wilderness that can serve as a source of species.
Park boundaries need to be drawn with the wildlife that use the area in mind. Often, species natural ranges extend beyond the park or preserve boundary and the species can be impacted or conflict with humans outside those areas.
Wildlife corridors between parks and nature preserves often function to allow the animals to interbreed and migrate among parks and are thought to increase the genetic diversity of the populations within the parks.

How much land should be left in parks or preserves?

About 10 % of the total land area of a country has been recommended, although there is no definitive amount that has been shown to be better than others.
Costa Rica and Kenya have placed 10 % or more in parks or reserves. France has 7 % in various regional parks, but only 0.7 in national parks.
The USA has 10.5 % in parkland and wild areas (98 million ha, mostly in the western states). Some US states have very little wilderness remaining, however (Table 13.2).

What is an edge effect?

This occurs when an "island" of forest is created and a disturbance zone is created along the edge of the new "island" of forest. Along the edge of the new isolated patch of forest, the area is disturbed, there is more light, more wind, and less protection. Some species disappear in this disturbed zone, and others that survive well in disturbance areas colonize the edge habitat.
There is a net loss of species from the cut area when it is cut off from the main forest, and an increase of those species in the adjoining areas. This is called the edge effect. If the island of forest is too small, the entire area may be influenced by the edge effect.

What is a wilderness area?

A wilderness area is a roadless area that is undisturbed by humans. If humans are present, they are visitors, not residents. In the USA there is a law (Wilderness Act of 1964) that specifically protects wilderness.
The law designates wilderness as "...an area of undeveloped Federal land retaining its primeval character and influence, without permanent improvement or habitation, which is protected and managed so as to preserve its natural conditions." In addition, it must be larger than 5000 acres (2025 ha).

How does the ocean regulate the Earth's climate?

Oceans buffer and moderate the air temperature of the Earth, making it less subject to extremes.
Because water has a high heat capacity, it stores a great deal of energy.
During the summer, ocean waters gain heat energy. They release it gradually during the fall and maintain a warmer air temperature than would be present without the ocean's influence.
Likewise, in the winter, oceans cool and maintain that coolness during the spring when the air is heating up.
Oceanic currents move the heat absorbed at the equator northward in the Northern Hemisphere, warming the land masses along which they flow. These currents return south with cool water, only to be warmed again. Thus, ocean currents distribute the sun's energy away from the equator.

What is a fishery?

A fishery is a predator-prey interaction in which humans are the predator and the prey are aquatic organisms. Thus, humans must always be part of a fishery management plan.
The aquatic organisms are typically fishes of various species, but may also be invertebrates (like clams, oysters, shrimp, and lobsters) and also vertebrates (like turtles, seals, and whales).
A commercial fishery is one in which the sole purpose is to capture aquatic organisms for profit.
A recreational fishery is one in which the harvest of aquatic species is for sport.
A subsistence fishery is one in which harvest is for food for the fishers.

How much fishery production is there worldwide?

The annual wild harvest for all world fisheries is more than 101.4 million metric tons per year (130 million U.S. tons/year).
Of this amount, marine fisheries produce 82 million metric tons per year (90.5 million U.S. tons/year), with the balance coming from fresh water fisheries.
The increase in fishery production has declined to 2 % per year from the rapid rate of increase (5 % per year) that was apparent in the post war period (1950-1970).

What is a fish stock?

A fish stock is simply a population.

What is overfishing?

When more fish are harvested than can be replaced via natural growth and reproduction. Basically, this is non-sustainable harvest of a fish stock.

What fisheries have been overfished?

There have been many notable cases, some of which have occurred even with active fishery management (Table 13.3).
The most famous of these was the Peruvian anchovy, which reached a peak in 1970 at 10 million metric tons, then has been in decline ever since.
Others overfished stocks include the North Atlantic cod and haddock off the New England coast, the Atlantic herring, the Atlantic menhaden, the North Sea herring, the Arctonorwegian cod, the Pacific salmon, and the Pacific sardines. It is also possible to overfish invertebrates like oysters in the Chesapeake Bay in the USA.

What happened in the case of the Peruvian anchovy fishery collapse?

This fishery has as its base the great wind-driven upwelling zone off the Peruvian coast, which brings nutrient-laden cool water from depth to the surface.
This upwelling stimulates an annual phytoplankton bloom, which is transferred up the food web to zooplankton and then the anchovies (this is a very short food chain).
The anchovies were harvested in order to make animal food, largely.
The maximum rates of harvest occurred in 1970 when 10 million metric tons were landed (or about a tenth of the world's total fish catch) , but in just 2 years, the catch had dropped to 1.8 million metric tons. Two things led to this change: overfishing and El Nino.
The El Nino is a condition in which the surface winds shift, the upwelling stops, the phytoplankton-based food chain is transferring a much smaller amount of energy to the anchovies. This El Nino is part of a climatic pattern that is unpredictable, but happens every 8 - 12 years.
However, after the El Nino year, the anchovies have remained rare. It appears that a combination of heavy fishing pressure along with the unpredictable cessation of upwelling , which caused the food base to decline, caused a long-term decline in anchovy abundance.

How are fisheries managed?

Even fisheries under science-based management plans have collapsed; so the management has been poor in the past.
Current management models rely on the logistic growth curve and mathematical models based on the concept of maximum sustainable yield (MSY; see Chapter 12). The biomass of fishes present in a region of the ocean and the carrying capacity (K) for that species is estimated by biologists using fishery catch data. Then, a portion of those fishes (usually, an amount that will lower the population to a size of K/2 ) are allowed to be harvested and this amount is allocated among commercial, recreational, and subsistence fishers according to guidelines established by regional fishery management councils.
In the USA, the regional councils are set up under the Magnuson Fishery Conservation Act and they govern fisheries in federal waters (3 miles - 200 miles offshore), with individual state management councils assuming management in waters closer than 3 miles.
Some species have small stocks and slow population growth rates (tuna and sharks) and thus low amounts of allowable catch (called quotas) are maintained. Other species have much larger populations and there are essentially no limits on how many can be harvested, but there may be limits on where or when they are harvested because of the unintentional catch, or bycatch, of other species (when shrimp are trawled, juvenile stages of other fishes, such as weakfish and red snapper, are caught in the nets).
Generally, because of the uncertainty over how big the stock sizes actually are (biologists must rely on poor data sets with huge error estimates), there is great controversy over the size of the quota to set (fishermen always want larger quotas).
Political arguments have developed routinely and invariably have lead to overharvest as the upper end of the biologist estimates are used to set quotas.
The fishermen win larger and larger quotas each year, until the stock collapses.

How many whales are there remaining in the world?

There are nine species of commercially harvested whales that are considered threatened or endangered remaining in the world's oceans (Table 13.4).
These whales were driven to near extinction largely by the overharvest of whaling ships. The rarest of these whales are the right whale and the blue whale, of which less than 5000 remain in all the world's oceans.
The blue whale is the world's largest animal, but has remained an endangered species despite the protection from whaling that it has received.
At the other end of the spectrum, the Minke whale, which number 700,000 or more, is not considered endangered. This is a smaller whale for which there is a limited, but still controversial, hunt by native subsistence fishers in Arctic waters. This whale has made up some of the diet and is used traditionally by native peoples in Greenland, Tonga, Japan, and among the Eskimo people in Alaska and Canada.
The gray whale, which was once considered endangered, has recently been removed from the endangered species list and is now regarded as threatened. There are now approximately 23,000 gray whales.

What did the Marine Mammal Protection Act (1972) do?

This legislation passed by the US Congress gave special protected status to whales, seals, dolphins, sea otters and other marine mammals.
Although many of these animals are endangered and have very low population sizes, some of them are far from endangered and appear to be undergoing population booms. Nonetheless, it is illegal to harm or kill these animals in any way.
Fisherman who inadvertently kill marine mammals (a bycatch problem) in their fishing operation can be subject to fines. This was a major problem in the tuna purse seine fishery of the Eastern Pacific Ocean, where over 100,000 spinner, spotted, and common dolphins were accidentally caught in the fishing nets because they feed along with the yellowfin tuna in schools.

Ecology In Your Back Yard

What kind of wood is in your home?
Where does the wood in your home come from?
How much paper do you use every day?
Where does the paper you use come from? Is any of it recycled?
How can you reduce paper usage and thus save trees?
Do you eat fish or shellfish?
Where does the fish and shellfish you eat come from?
What methods of harvest were used to capture the fish or shellfish?
Is there a bycatch problem in the fishery that your seafood comes from?
What species are being caught incidentally?
Use internet or library resources listed below to answer the questions above.
Please respond to these questions or send your thoughtful examples and comments to:

BackYard@wiley.com

The best responses will be posted on the Wiley Environet Website, so check the page regularly for updates to see if your e-mail is posted!

Hardcopy Links In The Library

Bardach, J. E., J. H. Ryther, and W. O. McLarney. 1972. Aquaculture: The Farming and Husbandry of Freshwater and Marine Organisms. Wiley Interscience, New York, NY. 868 pp.
Bell, F.W. 1978. Food From the Sea: The Economics and Politics of Ocean Fisheries. Westview Press. 380 pp.
Fordham, S.V. 1996. New England Groundfish: From Glory to Grief. A portrait of America's Most Devastated Fishery. Center for Marine Conservation. Washington, DC.
Perry, D. A. 1994. Forest Ecosystems. Johns Hopkins University Press. Baltimore. 649 pp.
Sherman, K., L. M. Alexander, and B. D. Gold (editors). 1990. Large Marine Ecosystems: Patterns, Processes, and Yields. American Association for the Advancement of Science. 242 pp.
Warner, W.W. 1994. Beautiful Swimmers; Watermen, Crabs, and the Chesapeake Bay. Little, Brown, and Company, Boston.

Ecolinks On The Web

http://www.igc.apc.org/ran/info_center/rates.html - The Rainforest Action Network (RAN). The commonly quoted rate of rainforest deforestation is 1 hectare/sec (or 2.47 acres/sec) which is equivalent to 2 football fields of rainforest/second. This amounts to the area the size of New York City lost per day, or an area the size of Poland lost per year.

http://forests.org/gaia.html - GAIA Forest Archive. Find out what's happening to rainforests and other forests around the world via the GAIA Forest Archive. These are short news reports about deforestation and politics worldwide.

http://schoolnet2.carleton.ca/english/virtprod/TREEVIA/gcg/treevia.html - Treevia. A trivia question and answer game about forests and trees provided by the Canadian Forest Service.

http://www.bc.com/eastside/eastside.htm - The Future of Western Forests by Boise Cascade Corporation. This website provides the viewpoint of a large forest product company on how it can achieve sustainability in forest harvests, while minimizing environmental impacts. Compare the diagrams illustrating forest management alternatives presented here (passive v. active management) with those depicted in Chapter 9. Is "passive management" any different than natural ecosystem succession? How do the endpoints of "passive management" and natural succession differ as presented in Chapter 9 and on this website?

http://www.epa.gov/docs/grd/forest_inventory/ - Map of the Forest Resources of the USA (US Forest Service). A map of the forested areas of the USA

http://www.for.nau.edu/forestry/other_sites.html - Forestry Websites. Various and sundry websites having to do with forestry.

http://remora.ssp.nmfs.gov/ - Fishery Statistics of the USA - up to date data on the biomass of fishes caught in the USA. Provided by the U.S. National Marine Fisheries Service (NMFS)

http://gopher.wh.whoi.edu/noaa.html - Woods Hole National Marine Fisheries Service Home Page A good source of information and pictures about fishes and fisheries of the US Atlantic Coast.