Ev Sci Ch 8

Ev Sci Ch 8

Questions from this chapter

• How can forests be better managed?

• How can grasslands be better managed?

• How can protected lands be better managed?

• How does the ecosystem approach help protect terrestrial biodiversity?

• How does the ecosystem approach help protect aquatic biodiversity?

  
  

How can forests be better managed?

Forests vary in age and structure

• Age refers to distribution of vegetation, horizontally and vertically

• Old growth forests - primary forest, uncut or regenerated forest that has not been seriously distubred by human activities

• Second growth forest - stand of trees resulting from secondary ecological succession.

• --Develop after trees have been removed by human activities

• Tree plantation - managed forest that contains only one or two species of trees that are all the same age

Tree Plantations

Less biologically diverse and sustainable than old growth and second growth forests

Forests help support life on Earth

• Forests provide vital ecosystem services

• -Forests remove carbon dioxide from the atmosphere

• --Stabilizes average atmospheric temperatures and climate conditions

Forests help support life on Earth

• Provide habitats for about two-thirds of Earth’s terrestrial species

• Maintain human health

• -Traditional medicines are mostly made from plant species native to forests

Fires impact forest structure

• Surface fires usually burn only undergrowth and leaf litter on forest floor

• Surface fires can be seen as beneficial

• Crown fires burn entire trees

How are surface fires beneficial?

• Burn away flammable material such as dry brush and prevent more destructive fires

• Free valuable plant nutrients trapped in slowly decomposing litter and undergrowth

• Release seeds from the cones of tree species

• Help control presence of destructive insects

Poor management negatively impacts forests

Impacts of timber harvest

• Building and using roads within forests increases topsoil erosion, sediment runoff, habitat fragmentation, biodiversity loss.

• Loggers will most often cut intermediate aged or mature trees from an area OR Clear cut

• Clear cut - removing all trees from an area.

• --Most efficient but most cost effective

• --Increases soil erosion, pollution, decreases biodiversity

• Strip cutting - clear cutting a strip of trees within a corridor narrow enough to allow natural forest to grow back within a few years

Impacts of deforestation

• Deforestation - temporary or permanent removal of large expanses of forests for agriculture, settlements, or other uses

• Destroys biodiversity

• Impacts rainfall in tropical forests

• --Water evaporating from trees plays a major role in rainfall there

• Reduces carbon absorption and contributes to climate change

People can harvest timber more sustainably

• Loggers recognize many sustainable forestry practices

• Include ecosystem services of forests in estimates of their economic value

• Identify and protect highly diverse forest areas,

• Stop logging in old growth forests

• Stop clear cutting on steep slopes

MORE PRACTICES

• Reduce road building in forests and rely more on selective cutting and strip cutting

• Leave most standing dead trees and larger fallen trees for wildlife habitat and nutrient cycling

• Grow tree plantations only on deforested and degraded land

• Certify timber grown using sustainable methods

People can better manage forest fires

• Smokey Bear campaign

• --1940s campaign to educate public about dangers of forest fires

• Ecologists warn that trying to prevent forest fires can actually make forests more vulnerable to fires in the long run

• Increases likelihood of destructive crown fires due to accumulation of flammable underbrush.

Strategies for limiting harmful effects of forest fires.

• Use carefully planned and controlled fires, called prescribed burns, to remove flammable underbrush

• Allow some fires on public lands to burn underbrush and small trees

• Protect houses and other buildings in fire prone areas by thinning trees and other vegetation in a zone around them and eliminating the use of highly flammable construction materials such as wood shingles

• Use solar powered microdrones equipped with infrared sensors to detect forest fires and monitor progress in fighting them

People can reduce demand for harvested trees

• Methods to reduce tree demand

• Choose reusable plates, cups, napkins

• Produce tree-free paper

People can reduce tropical deforestation

• Debt for nature swaps - participating countries act as custodians of protected forest reserves in return for foreign aid or debt relief

• Conservation concessions - paying governments or landowners in other nations to preserve their land’s natural resources for a set amount of time

How can grasslands be better managed?

Grasslands are overgrazed

• Grasslands provide many ecosystem services

• --Soil formation, erosion control, nutrient cycling, storage of atmospheric CO2 in biomass

• Rangelands - unfenced grasslands in temperate and tropical climates that supply forage, or vegetation for grazing and browsing animals.

• Pastures - managed grasslands that are often planted with domesticated grasses or other forage crops.

Overgrazing

Overgrazing - when too many animals graze an area for too long, damaging grasses and their roots and exceeding carrying capacity.

Exposes topsoil, compacts the soil (reduces capacity to hold water)

Rangelands can be protected

• Timing of grazing can be controlled

• --Avoid grazing an area at the same stage of plants growth every year

• --Limiting amount of animals grazing in a certain area

• Rotational grazing

• --Cattle are moved to new location after a few days

• Suppressing growth of undesirable plants by using herbicides

How can protected lands be better managed

The World’s parks face many challenges

• 6600 major national parks in more than 120 countries

• Visitors are degrading features of the park.

• People illegally take resources from the park

US national parks are challenged

• 59 major national parks

• Human activities damage the parks

• Nonnative species disrupt parks

People can set aside more areas for protection

• Buffer zones - strictly protecting inner core of a reserve as well as establishing another outer cone in which local people can extract resources sustainably.

• UN used the buffer zone concept to create global network of 651 biosphere reserves in 120 countries

• Wilderness Areas - protected by law from activities that could alter their ecology.

• --Forestry, road and trail development, mining, building are not allowed

How does the ecosystem approach help protect terrestrial biodiversity?

The Ecosystem Approach: A five point plan

• Plan focuses on protecting threatened habitats and their ecosystem services

Protecting Biodiversity Hotspots

• Biodiversity hotspot - areas that are rich in highly endangered endemic species

• --Also threatened by human activities

• Two criteria to qualify as a hotspot

• --Must have lost 70% of its original habitat

• --Must contain at least 1500 endemic species

Protecting Biodiversity Hotspots

• Protecting ecosystem services

• --Humans degrade 60% of the ecosystem services provided by various ecosystems worldwide

• --We need to identify and protect areas in which vital ecosystem services are at risk.

Restoring damaged ecosystems

• It is possible to reverse much of the damage to ecosystems caused by human activities

• Ecological restoration - can help return a damaged habitat or ecosystem to its original one

• --Replanting forests, reintroducing native species, removing harmful invasive species, removing dams, restoring grasslands, coral reefs, wetlands, stream banks

How does the ecosystem approach help protect aquatic diversity

Human activities are threatening aquatic biodiversity

• Human activities have destroyed much of the world’s coastal wetlands, coral reefs, and mangroves, and even the ocean floor.

• Pollution, overfishing, dam building, excessive water withdrawal,

• Overfishing

Overfishing

• Fishery - a concentration of an aquatic species suitable for commercial harvesting in an ocean area or inland body of water.

• 4.4 million fishing boats harvest fish from oceans

• Commercially valuable fish (cod, marlin, swordfish, tuna) are becoming scarce because of overfishing

Ocean acidification threatens aquatic biodiversity

• Coral reefs are exposed to warmest, most acidic ocean waters of the last 400k years

• Ocean waters absorb CO₂ from the atmosphere, making the water more acidic

• Fastest way to reduce ocean acidification would be reducing the use of fossil fuels.

Dead zones threatens aquatic biodiversity

• Pollution from excess soil nutrients sometimes causes oxygen depleted areas in the ocean called dead zones.

• Dead algae that sinks to the bottom decomposes, which requires oxygen. This drains oxygen levels in the area, causing marine organisms to suffocate

Protecting Marine Biodiversity is difficult

• Human ecological footprint and fishprint are expanding very rapidly, difficult to monitor

• Creating marine reserves offers protection for marine species

• Marine reserves face challenges in funding, management, and monitoring.