chapter 8 notes

Sustaining Biodiversity: An Ecosystem Approach

Case Study: Costa Rica—A Global Conservation Leader

  • Costa Rica is an oasis of biodiversity due to its tropical location and government commitment to conservation, despite natural capital degradation.

  • Estimated 500,000 plant and animal species.

  • The reserve system includes more than 25% of the nation’s land.

  • The government pays landowners to conserve land.

  • Governments must meet people’s needs while protecting ecosystems and wildlife.

How Can Forests Be Better Managed?

  • The world’s forests cover one-third of the land area and provide essential ecosystem services:

    • Store carbon dioxide.

    • Support energy flow.

    • Nutrient cycling.

    • Produce oxygen.

    • Reduce erosion.

    • Absorb/release water.

    • Purify air and water.

    • Influence climate.

    • Provide habitat.

  • Forests also provide economic services:

    • Wood for fuel.

    • Lumber.

    • Wood products.

    • Pulp.

    • Mining.

    • Grazing.

    • Recreation.

    • Jobs.

Forests Vary in Age and Structure

  • Categorized based on age and structure:

    • Old-growth (primary) forests: uncut or regenerated forests not seriously disturbed by human activity or natural disasters for 200 years.

    • Second-growth forests: result from secondary ecological succession—after the primary forests have been destroyed.

    • Tree plantations: managed farms growing only one or two species, all the same age.

Fires Impact Forest Structure

  • Surface fire

    • Usually only burns undergrowth and leaf litter.

    • Kills seedlings and small trees, but spares most mature trees; allows most wildlife to escape.

    • Can be beneficial: burns away flammable material, frees nutrients, releases some seeds, helps control destructive insects and tree diseases.

  • Crown fire

    • Leaps from treetop to treetop, burns whole trees, kills wildlife, and damages buildings.

There Are Several Ways To Harvest Trees

  • Selective cutting: intermediate-aged or mature trees are cut singly or in small groups.

  • Clear-cutting: all trees are removed from a geographic area.

    • Most efficient and least costly, but harms ecosystems.

  • Strip cutting: trees are removed in sections parallel to a feature, such as a road.

Impacts of Deforestation

  • Deforestation: temporary or permanent removal of large areas of forest for agriculture, settlements, and other uses.

    • Has eliminated almost 50% of all forests in the last 8,000 years.

    • Other negative impacts:

      • Erosion (pollutes water, degrades soil).

      • Increased flooding.

      • Local extinction of specialist species.

      • Release of CO2/loss of CO2 absorption.

Tropical Forests Are Rapidly Disappearing

  • At least 1/2 of mature tropical forests (home to at least 1/2 of the world’s known species) have been lost since 1950.

  • From 2000–2013, more than the equivalent of 50 soccer fields of tropical forest were lost every minute.

  • Rapid deforestation is taking place in Africa, Southeast Asia, and South America.

Causes of Tropical Deforestation

  • Pressures from population growth/poverty.

  • Government subsidies for large-scale logging and ranching.

  • Direct causes vary according to geography:

    • South America: cattle grazing and crop land.

    • Indonesia/Southeast Asia: oil palm plantations.

    • Africa forests: firewood and farming.

Impacts of Deforestation on Rain Forests

  • Deforestation Cycle:

    • Build roads, harvest biggest/best trees, sell land to ranchers (burn and clear land for grazing), sell to farmers/settlers, land becomes useless.

  • Effects

    • Destroys biodiversity.

    • Reduces rainfall, leads to drier conditions.

    • Causes topsoil erosion.

    • Global reduction of CO2 absorption, burning and clearing add CO2 to the atmosphere.

We Can Manage Forests More Sustainably

  • Recognize the value of ecosystem services.

  • Use more selective cutting in forests.

  • Phase out government subsidies and tax breaks that favor deforestation.

  • Certify lumber/wood products as sustainable, full cost pricing for consumers.

  • Economic rewards for sustainable forestry.

  • Encourage tree planting programs and protect diverse forest areas.

We Can Improve the Management of Forest Fires

  • Strategies for reducing fire-related harm:

    • Use controlled, prescribed burns to remove small trees and underbrush in high-risk areas.

    • Allow fires on public land to burn as long as they do not threaten human life or structures.

    • Have thin trees/vegetation around buildings.

    • Eliminate the use of wood shingles and siding in construction.

    • Use solar-powered micro-drones for early forest fire detection.

We Can Reduce the Demand for Harvested Trees

  • 60% of the wood consumed in the United States is wasted. How can this be reduced?

    • Use other non-tree fibers such as kenaf and hemp to yield more pulp per acre and require less pesticide use.

    • Limit the use of throwaway paper products made from trees and use reusable products.

    • Stop cutting fuelwood from forests, establish plantations of fast-growing trees and shrubs for fuel sources.

There Are Several Ways To Reduce Tropical Deforestation

  • Provide foreign aid or debt relief for sustainable forestry (debt-for-nature swaps, conservation concessions).

  • Crack down on illegal logging and create conservation reserves.

  • Subsidize tree planting (government).

  • Buy only wood and wood products certified sustainable (consumers).

  • Reduce poverty and slow population growth.

How Can Grasslands Be Better Managed?

  • Grassland productivity can be sustained and improved by:

    • Controlling the abundance and distribution of grazing livestock.

    • Restoring degraded rangeland.

Grasslands Are Important Ecosystems

  • Grasslands cover about one-quarter of Earth’s landmass and are the most widely used/altered ecosystems other than forests.

  • Rangelands: unfenced, tropical/temperate grasslands that supply forage for grazing.

  • Pastures: managed grasslands/fenced meadows that are often planted with domesticated grasses or other forage crops.

Grasslands Are Overgrazed

  • Overgrazing occurs when too many animals graze an area for too long, exceeding the area’s carrying capacity.

  • Impacts of overgrazing:

    • Harms grass roots.

    • Reduces grass cover.

    • Causes soil erosion/compaction, lowers soil’s capacity to hold water.

    • Leads to the invasion of plants that cattle will not eat.

Rangelands Can Be Protected

  • Sustainable grazing methods:

    • Control the number of grazing animals.

    • Avoid grazing an area at the same time of plant growth year after year or during the growing season.

    • Consider livestock diets, match to suitable areas.

    • Use rotational grazing.

    • Use herbicides, mechanical removal, or controlled burning to suppress invasive species.

    • Permit short-term trampling by livestock to destroy the root systems of unwanted plants.

How Can Protected Lands Be Better Managed?

  • More effective protection measures are needed for existing parks and natural reserves (and much of Earth’s undisturbed land areas) to sustain their biodiversity.

The World’s Parks Face Many Challenges

  • Many are too small to maintain large animal species.

  • Many are challenged with invasive species.

  • Some are so popular that the number of visitors degrades the very features that made them attractive in the first place.

  • Internationally, many are used illegally for gathering firewood, hunting (poaching), logging, and mining.

U.S. National Parks Are Also Challenged

  • The National Park System includes 59 major national parks and 339 national monuments and historic sites.

  • Popularity is one of the biggest challenges to U.S. National Parks.

  • Many parks become islands of biodiversity.

  • The loss of keystone species hurts park ecosystems (e.g., wolves in Yellowstone).

Nature Reserves Occupy Only a Small Part of Earth’s Land

  • Less than 13% of Earth’s land is either strictly or partially protected; less than 6% is strictly protected from potentially harmful human activity.

  • Beneficial impacts to reserves can be increased by establishing buffer zones (strict protection of a reserve’s inner core) to manage nature reserves (biosphere reserves).

Protecting Wilderness Is an Important Way to Protect Biodiversity

  • Undeveloped lands can be protected from exploitation by designating them as wilderness areas.

    • Activities that alter the ecology of such areas are not allowed (forestry, road and trail development, mining, and building construction).

    • Areas protected by the Wilderness Act (established in the mid-1960s) have grown nearly twelve-fold since the Act’s inception.

    • Offer “ecological insurance policy.”

How Does the Ecosystem Approach Help Protect Terrestrial Biodiversity?

  • By identifying and protecting biodiversity hotspots, employing restoration ecology and reconciliation ecology, we can help sustain terrestrial biodiversity and protect ecosystem services.

The Ecosystem Approach

  • Five-point Plan:

    • Inventory all of the species found in terrestrial ecosystems along with the ecosystem services they provide.

    • Identify threatened terrestrial ecosystems with potential for recovery.

    • Protect endangered plants/ecosystem services.

    • Restore degraded ecosystems.

    • Make development biodiversity-friendly—provide financial incentives/tax breaks for conservation.

Protecting Global Biodiversity Hotspots Is an Urgent Priority

  • Take emergency measures to rapidly protect terrestrial biodiversity hotspots.

    • Rich in highly endangered endemic species and threatened by human activities.

    • Has lost at least 70% of its original habitat and contains at least 1,500 endemic species of vascular plants.

    • Cover little more than 2% of Earth’s surface but are estimated to contain approximately 50% of the world’s flowering plants and terrestrial vertebrates.

    • Only about 5% are truly protected.

Protecting Ecosystem Services

  • The 2005 UN Millennium Ecosystem Assessment outlined how to sustain vital ecological and ecosystem services by protecting reserves/biodiversity hotspots.

  • Residents, public officials, and conservation scientists need to work together in developing win-win protection strategies for ecosystem services, creating “life raft” ecosystems.

Restoring Damaged Ecosystems

  • Repair ecosystem damage and enhance ecological succession by:

    • Ecological restoration: returning degraded habitats and ecosystems as close as possible to their natural state.

    • Rehabilitating ecosystems without trying to restore their original condition.

    • Replacing degraded ecosystems, like forests, with productive pastureland.

    • Creating artificial ecosystems.

Scientific Strategies For Ecological Restoration and Rehabilitation

  • Identify the causes of degradation (pollution, overgrazing, mining, invasive species, etc.).

  • Stop degradation by eliminating or reducing the factors listed above.

  • Reintroduce keystone species to restore natural ecological processes.

  • Protect degraded areas to encourage natural recovery.

Reconciliation Ecology: Sharing Our World With Other Species

  • How can we reconcile biodiversity conservation and human development?

    • Conserve species diversity in places where humans dominate.

    • Use sustainable forms of ecotourism to protect local wildlife and ecosystems.

    • Teach local populations to protect local wildlife and ecosystems and to manage ecotourism to provide win-win sustainability.

How Does the Ecosystem Approach Help Protect Aquatic Biodiversity?

  • Establishing protected sanctuaries, managing coastal development, reducing water pollution, and preventing overfishing can help sustain aquatic biodiversity and increase beneficial human environmental impacts.

Human Activities Are Destroying and Degrading Aquatic Biodiversity

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

    • Threats to freshwater systems: habitat loss, degraded water flows, biodiversity loss (dam building, excessive water withdrawal).

    • Threats to marine systems: dredging, trawling, changing sea levels, and warming ocean waters.

  • Trawling is one of the largest human-caused disturbances to the biosphere.

Overfishing

  • Industrial fishing fleets supply the growing global demand for seafood by using GPS equipment, fish-finding devices, huge nets, long fishing lines, spotter planes, and refrigerated factory ships that process and freeze their enormous catch.

    • Severely reduces marine biodiversity.

    • Degrades important marine ecosystem services.

Fishprints: Similar in Nature to Ecological Footprints

  • Defined as the area of the ocean needed to sustain the fish consumption of an average person, the nation, or the world.

  • Fishery: concentration of aquatic species suitable for commercial harvest.

  • Overfishing has led to the collapse of some of the world’s major fisheries.

    • Rapidly reproducing invasive species take over and disrupt ocean food webs when predator species dwindle.

Ocean Acidification

  • Coral reefs are exposed to the warmest, most acidic ocean waters of the past 400,000 years.

    • Changes are tied to the increase in atmospheric CO2.

    • Earth’s oceans have absorbed one-fourth of the excess CO2.

  • Changes the chemistry of ocean water, making it more acidic.

  • Less availability of bicarbonate ions hurts phytoplankton, corals, sea snails, crabs, oysters, and other organisms that use bicarbonate ions to form shells and skeletons.

  • These structures may even dissolve.

Dead Zones

  • Pollution from excess soil nutrients causes oxygen-depleted “dead zones” in the ocean.

    • Fertilizers wash off farm fields, carried downstream into oceans.

    • Causes overgrowth of algae, which die and sink to the ocean bottom.

    • Bacteria break down algae, using up oxygen in the process, which kills/drives away organisms that cannot get the oxygen they need; the area becomes lifeless.

Can We Protect and Help Sustain Marine Biodiversity?

  • Protection is possible but difficult because:

    • Fishprints and ecological footprints are expanding exponentially.

    • Ocean damage is not highly visible to humans.

    • People incorrectly view the ocean as an inexhaustible resource.

    • Most of the world’s ocean area lies outside the legal jurisdiction of any country, leading to overexploitation—a classic example of the tragedy of the commons.

We Can Better Protect Marine Ecosystems

  • Marine Protected Areas:

    • Established by IUCN, with more than 5,800 worldwide.

    • 41% of U.S. waters are protected in some manner.

    • MPAs only offer partial protection and are often too small.

  • Marine reserves:

    • Offer full protection from human disturbance.

    • Allow quick recovery of fish populations and species diversity.

Taking an Ecosystem Approach to Sustaining Aquatic Biodiversity

  • Some proposals:

    • Complete the mapping of the world’s aquatic biodiversity.

    • Identify and preserve the world’s aquatic biodiversity hotspots.

    • Create large/fully protected marine reserves to promote marine ecosystem recovery.

    • Initiate global ecological restoration projects.

    • Reduce poverty in areas near protected lands and waters.