Essentials of Ecology

CONCEPT 10-3 231

Protect the most diverse and

endangered areas

Educate settlers about

sustainable agriculture and

forestry

Subsidize only sustainable

forest use

Protect forests with

debt-for-nature swaps and

conservation concessions

Certify sustainably grown

timber

Reduce poverty

Slow population growth

Encourage regrowth

through secondary

succession

Rehabilitate degraded

areas

Concentrate farming

and ranching in

already-cleared areas

SOLUTIONS

Sustaining Tropical Forests

Prevention Restoration

Figure 10-19 Ways to protect tropical forests and use them more sustainably

(Concept 10-2). Question: Which three of these solutions do you think are the

most important? Why?

of protected forest reserves in return for foreign aid or

debt relief. In a similar strategy called conservation con-

cessions, governments or private conservation organiza-

tions pay nations for concessions to preserve their nat-

ural resources.

Loggers can also use tropical forests more sustain-

ably by using gentler methods for harvesting trees. For

example, cutting canopy vines (lianas) before felling a

tree and using the least obstructed paths to remove the

logs can sharply reduce damage to neighboring trees.

In addition, governments and individuals can mount

efforts to reforest and rehabilitate degraded tropical

forests and watersheds (see Individuals Matter, at left)

and clamp down on illegal logging.

Finally, each of us as consumers can reduce the

demand that fuels illegal and unsustainable logging in

tropical forests. For building projects, we can use sub-

stitutes for wood such as bamboo and recycled plastic

building materials (Concept 10-2). Recycled waste lum-

ber is another alternative, now marketed by companies

such as TerraMai and EcoTimber.

We can also buy only lumber and wood products

that are certified as sustainably produced (Science

Focus, p. 228). Growing awareness of tropical defores-

tation and the resulting consumer pressure caused the

giant retail company Home Depot to take action. It re-

ported in 2007 that 80% of the wood it carries meets

such certification standards.

These and other ways to protect tropical forests are

summarized in (Figure 10-19).

10-3 How Should We Manage and Sustain Grasslands?

CONCEPT 10-3 We can sustain the productivity of grasslands by controlling the

number and distribution of grazing livestock and by restoring degraded grasslands.

▲

Some Rangelands Are Overgrazed

Grasslands provide many important ecological services,

including soil formation, erosion control, nutrient cy-

cling, storage of atmospheric carbon dioxide in biomass,

and maintenance of biodiversity.

After forests, the ecosystems most widely used and

altered by human activities are grasslands. Range-

lands are unfenced grasslands in temperate and

tropical climates that supply forage, or vegetation, for

grazing (grass-eating) and browsing (shrub-eating) ani-

mals. Cattle, sheep, and goats graze on about 42% of

the world’s grassland. The 2005 Millennium Ecosystem

Assessment estimated that continuing on our present

course will increase that percentage to 70% by 2050.

Livestock also graze in pastures—managed grasslands

or enclosed meadows usually planted with domesti-

cated grasses or other forage.

Blades of rangeland grass grow from the base, not

at the tip. So as long as only the upper half of the blade

is eaten and its lower half remains, rangeland grass is a

renewable resource that can be grazed again and again.

Moderate levels of grazing are healthy for grass-

lands, because removal of mature vegetation stimulates

rapid regrowth and encourages greater plant diversity.

The key is to prevent both overgrazing and undergraz-

ing by domesticated livestock and wild herbivores.

Overgrazing occurs when too many animals graze for

too long and exceed the carrying capacity of a range-

land area (Figure 10-20, left, p. 232). It reduces grass

cover, exposes the soil to erosion by water and wind,

and compacts the soil (which diminishes its capacity