Habitat Loss, Modification & Fragmentation

how much of the worlds lands surface been transformed by humans

83%

how much of the Earth’s ecosystems are considered degraded or unsustainably used

60%

What are most affected and why?

Temperate grasslands, savannahs, and shrublands

agriculture use

how much of coral reefs have been destroyed? how much are degraded?

20% destroyed

50% degraded

Habitat loss

impacts so severe that all or nearly all species affected

Habitat degradation

impacts that negatively affect many but not all species; reduction in the capacity of an ecosystem to support some subset of species

habitat modification

as above but a general term; used without the knowledge of specific degradation for a given species or group of species

Habitat transformation/conversion

as above but used when referring to conversion of forest to cropland

since 1960 the human population has doubled, and we have lost how much native vegetation in the US?

58%

Some ecosystems have been completely eliminated such as

native grasslands in California, floodplain wetlands, and streams in Mississippi and old growth forests across most of the US

over the past 3 centuries

about half of the world’s forest cover has been removed to make way for croplands, pasture, and settlements

in 25 countries no forest remains; in 29 other countries

countries >90% of forest has been lost

Europe has the least forest cover of any continent. Why?

most was lost before 1700 due to agriculture

Between 1990 and 2000, the proportion of the Earth’s land area covered by forest decreased from

30.4% to 29.7%

Forests in the eastern U.S. were almost completely removed by

1850, but many are regenerating

forest provides many ecosystem services including

regulating water supplies by mediating flow rates, controlling erosion, and affecting climate change through gas exchange

How much of the world depends on water flows through forests for their water supply?

2/3

What do cities protect?

nearby forested watersheds for drinking water (e.g., Catskills for NYC; Blue Mountains for Sydney, Australia)

heavy deforestation in a watershed increases

runoff and can cause flash flooding of cities and villages

deforestation in the tropics is expected to increase what?

regional and global warming

• The Amazon rainforest has shifted from being a carbon sink to a major source of CO2 emissions

• This will be exacerbated by the increase of fires

Loss or degradation of grasslands, savanna, and shrubland habitats

• Found in dry subtropical or dry-humid temperature climates; cover 41% of the Earth’s surface

• Maintained by drought, fire, freezing, or grazing by wild ungulates

• Provide ideal conditions for agriculture and grazing livestock; and so have been transformed worldwide

• Temperate grasslands have been the hardest hit; mostly due to agriculture but also due to urbanization

• Example: prairie ecosystems in the U.S.; 97% of tallgrass prairies and 60% of mixed-grass and shortgrass prairies have been lost, mainly to agriculture and grazing

Desertification

• Middle East, Asia, north and east Africa

• Through a combination of climate change & human action, dry forests are replaced by grasslands, and fragile woodlands are transformed into scrublands and deserts

• Prior to drying these landscapes were a mosaic of woodlands and grasslands, but were later ‘converted’ to shrublands or deserts partly due to felling

• As local conditions became drier the forests and woodlands cannot recover

Degradation of freshwater systems

• Freshwater degradation occurs through water diversions, dams, and wetland losses; this is due mainly to agricultural and urban expansion

• Regulation of river flows for agricultural and city use has become the norm: Only 2% of U.S. rivers run unimpeded. Worldwide, < 1/3 of all rivers are unimpeded

• 91% of federally endangered U.S. freshwater fishes owe their listing to water development; 98% for mussels

• Agriculture and land clearing lead to sedimentation in wetlands and streams; deep faster flows change to more shallow, stagnant water

Land clearing affects river/stream turbidity

“Turbidity — the condition that makes water cloudy and interferes with chlorination to eliminate contaminants — appears to be getting worse because of changing weather patterns and increasing runoff from land development upstate. If the city cannot find a permanent solution to the silt, it may not be able to avoid building a huge filtration plant that could cost about $8 billion.” – New York Times, 2006

Degradation of marine ecosystems

• 60% of the world’s human population lives < 100 km from the coast

• Thus, 20% of lands adjacent to oceans have been highly modified

• Plus, those populations are often highly dependent on marine resources for food or income

• Impacts include toxic chemicals, solid waste and nitrogen enrichment

• Invasive species are ever increasing

Degradation of Estuaries

• Many have been altered or destroyed through filling, draining, dredging, shoreline stabilization, and conversion for agriculture

• Some vast deltas that once channeled the flows of large rivers have been reduced to a trickle (e.g., Nile, Colorado, Ganges)

• Sediments are trapped behind dams and impoundments, depriving estuaries of nutrients, which interrupts food webs and alters the ecosystem; the loss of fresh water changes animal communities on which fisheries are reliant upon

• The lack of sedimentation due to levees has caused the loss of coastline (marshes), especially in Louisiana

Degradation of Coral Reefs

Coral reef systems have suffered from degradation due to pollution, sedimentation, direct exploitation of corals, destructive fishing at reefs, and disease outbreaks and bleaching due to climate warming

Human activities that cause habitat degradation

The main proximate causes of habitat degradation & loss are

1. Agricultural activities (crop & livestock farming, timber plantations, aquaculture)

2. Extraction activities (mining, fisheries, logging, harvesting)

3. Development (human settlements, industry, infrastructure)

4. War & violent conflict

Agriculture

• Historically the primary cause of ecosystem change, fuelled by the industrial revolution

• 98% of arable lands have been transformed, including almost complete loss of entire ecosystems (e.g., tallgrass prairie in the U.S.)

• >70% of all land areas in Europe and South Asia are under cultivation

• Most croplands are used to grow annual crops such as wheat, rice, and soybeans

Intensive agriculture

• Includes vast, irrigated monocultures heavily treated with pesticides, herbicides and fertilizers

• These ‘agroecosystems’ have replaced natural ecosystems, especially in western Europe and the U.S.

• Less intensive agricultural practices can be more compatible with biodiversity (e.g., an agricultural matrix with remnants of native vegetation)

Biodiversity in the Australian rice industry

• 1 million tons of rice sold to 60 countries worldwide

• Grown in a semi-arid zone = irrigated crop

• Water taken from rivers and aquifers has caused significant environmental damage

• The industry was interested in developing a ‘greener’ image by showing stewardship through environmental initiatives

• I led a team that looked to quantify biodiversity on rice farms, and to determine the drivers of that biodiversity

Some major findings from Dr. Doody’s study on biodiversity in the Australian rice industry

• 179 species of vertebrates on 10 farms

• Species richness significantly higher on farms with remnant vegetation patches (N=69 spp) vs. farms without patches (N=49 spp)

• Abundance also much higher on farms with vegetation remnants for all groups except frogs

• >500 million spotted grass frogs produced annually in rice bays!

• Turtle used rice bays as a surrogate for natural temporary wetlands

• Pythons overwintered in attics and in hollow trees; they consumed mostly house mice

Land sparing

• some natural habitats

• some high-yield farmland

• High-yield farmland delivers food production over a smaller area so land elsewhere in the region can be spared as natural habitat

Land sharing

wildlife-friendly farmland everywhere

entire region managed as wildlife-friendly farmland, which shares the function of food production and biodiversity conservation

to maintain overall food production, there’s no room for natural habitat

Pastures

• Highly-modified pasturelands make up 6-14% of current land cover worldwide, depending on long-term or overall use

• In many cases pastures are mismanaged until they are no longer useful for livestock (e.g., desertification)

• Comparisons of degradation by use type:

  • Agricultural mismanagement = 550 million hectares

  • Livestock mismanagement = 680 million hectares

extraction

• Logging, mining and quarrying can devastate habitats and create soil disturbances that can take centuries to recover

  • 60% of all threatened species of plants are threatened by logging or mining

• Strip mining and exploitation and refinement of oil & gas resources can lead to wide-scale habitat degradation, especially in coastal areas

• Some fisheries practices have devastating impacts on ocean bottoms

Urbanization & Infrastructure

• The most extreme transformation (habitat loss); 3 % of the Earth’s surface is urban, supporting half of the world’s population

• Therefore, although 3% is low, the ecological footprint is enormous

• For example, London has a footprint 125 X its area; this is equivalent to the productive lands of the entire UK to support 12% of the population!

War & violent conflict

• War and violent conflict creates vast numbers of refugees that have detrimental impacts on land (wood for fuel, animals for food).

• Recent examples include the Democratic Republic of Congo, Afghanistan, Madagascar