Environmental Issues & Problems ENV 150. What do we mean by biodiversity? What do we mean by biodiversity? What do we mean by biodiversity?

Transcription

1 REVIEW Environmental Issues & Problems ENV 150 What do we mean by biodiversity? Guillaume Mauger Today: Loss of Biodiversity REVIEW REVIEW What do we mean by biodiversity? What do we mean by biodiversity? U.S. Office of Technology Assessment: Biological diversity refers to the variety and variability among living organisms and their relative frequency. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, genes, and their relative abundance. More than just diversity of species: Diversity of ecosystems Diversity of species Diversity within a species (genetic)

2 REVIEW Why is biodiversity important? In other words: What is the value in biodiversity? REVIEW Valuing Biodiversity Ecosystem Services Provisioning services Food, water, timber, fiber Regulating services Regulation of climate, floods, disease, wastes, and water quality Cultural services Recreation, aesthetic enjoyment, spiritual fulfillment Supporting services Soil formation, photosynthesis, nutrient cycling source: Millennium Ecosystem Assessment, Ecosystems and Human Well-being: Biodiversity Synthesis. REVIEW Valuing Biodiversity Ecosystem Services Provisioning services! Most Food, values water, timber, are fiber assigned by humans Regulating services Regulation of climate, floods, disease, wastes, and! Most water are quality related to human survival Cultural services Recreation, aesthetic enjoyment, spiritual fulfillment Supporting services Soil formation, photosynthesis, nutrient cycling source: Millennium Ecosystem Assessment, Ecosystems and Human Well-being: Biodiversity Synthesis. REVIEW Valuing Biodiversity Use values Direct uses of biodiversity: consumptive - food, medicines, non-consumptive - eco-tourism Subject to trade & commerce, monetary value readily assigned, varies with demand Non-use values Indirectly related to humans, ecosystem services, future options, aesthetics Monetary valuation difficult Intrinsic value Worth in themselves source:

3 Valuing Biodiversity Valuing Biodiversity, examples Ecotourism worldwide generates from $950K to $1.8M per minute! e.g.: Kenyan lion, living to age 7: $515K in ecotourism, or $1K for its skin Kenyan elephant, living to age 60: $1M in ecotourism, or $20-100K for its tusks Source: Michael Soulé Valuing Biodiversity, examples Today s Focus: Species How many do we have? Estimated: 4 to 100 million animal & plant species Documented: ~1.5M animal, ~400K plant species

4 Today s Focus: Species How many do we have? Estimated: 5 to 30 million animal & plant species Documented: ~1.5M animal, ~400K plant species Today s Focus: Species What s the natural rate of extinction? Source: Millenium Ecosystem Assessment Today s Focus: Species What s the natural rate of extinction? Today s Focus: Species What s the natural rate of extinction? First, definitions: Local extinction - no longer found in a specific area (loss of a population) Background extinction rate: one extinct species per million species per year: % / yr Ecological extinction - too few to serve ecological role Biological extinction - 100% gone.

5 Today s Focus: Species What s the natural rate of extinction? Background extinction rate: one extinct species per million species per year: % / yr Today s Focus: Species What s the natural rate of extinction? Background extinction rate: one extinct species per million species per year: % / yr How is this estimated? How is this estimated? Field surveys Fossil record Species-area relationships Mathematical models Documenting Changes in Biodiversity Earth s History: Mass Extinctions = catastrophic, widespread event. = Loss of 25-95% of species within a relatively short period of time (<5M yrs) (e.g.: extinction of the dinosaurs) The Far Side, G. Larson we ve had ~5 in the past 500 million years.

6 Today: 6th mass extinction Today: 6th mass extinction All available evidence points to a sixth major extinction event currently underway. Unlike the previous five events, which were due to natural disasters and planetary change the current loss of biodiversity is mainly due to human activities. -UNEP State and Trends of the Environment, 2007 IUCN Red List, definitions The International Union for the Conservation of Nature, Red List of Threatened Species: ENDANGERED (EN) Considered to be facing a very high risk of extinction in the wild. THREATENED / VULNERABLE (VU) Population does not qualify as Endangered but is still at risk. Likely to become endangered: risk of extinction is still high. IUCN Red List, example species (International Union for Conservation of Nature) Questions to answer for yourselves: About the species & its niche type, habitat, diet, niche, etc. Status (i.e., endangered, threatened, etc.) How its status was estimated Reasons for its current status Change in status over time Threats Past, present, future source:

7 Millenium Ecosystem Assessment, stats Over half of the 14 biomes that the MA assessed have experienced a 20-50% conversion to human use Across a range of taxonomic groups, the population size or range (or both) of the majority of species is declining. Over the past few hundred years, humans have increased species extinction rates by as much as 1,000 times background rates that were typical over the Earth s history. source: Millenium Ecosystem Assessment, stats 16,928 plant and animal species are known to be threatened with extinction. This may be a gross underestimate because less than 3% of the world s 1.9 million described species have been assessed by the IUCN In the last 500 years, human activity is known to have forced 869 species to extinction 1 in 4 mammals and 1 in 8 birds face a high risk of extinction in the near future 1 in 3 amphibians and almost half of all tortoises and freshwater turtles are threatened. source: Millenium Ecosystem Assessment What makes a species vulnerable to threats / extinction?

8 What makes a species vulnerable to threats / extinction? Big, slow, tasty, or with valuable parts. Characteristics of vulnerable species Low reproductive rate Specialized niche Narrow distribution Feeds at high trophic levels Fixed migratory patterns Rare Commercially valuable Large territories What are the causes of species decline? Direct Causes ( drivers ) Habitat change Land use (e.g., conv. to agriculture) River modifications Loss of corals Sea floor damage (e.g., due to trawling) Invasives Population and Resource Use Pollution Climate Change Overexploitation By far the most important driver ( HIPPCO, in book)

9 Direct Causes ( drivers ) Habitat loss Affects: 89% of threatened birds 83% of threatened mammals 91% of threatened plants Island species (often endemic) vulnerable to habitat destruction / degradation e.g.: mountain tops, islands, freshwater lakes, national parks Habitat Fragmentation Blocks migration Smaller, more vulnerable populations Barriers to disperse into new areas, reproduce, find food Habitat loss Invasives Affects: 30% of threatened birds 5% of threatened plants Problem: some have no natural limits to population growth i.e.: no Environmental Resistance Examples: 98% of US food supply is from introduced species Zebra mussel other examples?

10 Over-exploitation Pollution Affects: 37% of threatened birds 34% of threatened mammals 8% of threatened plants 8% of threatened reptiles Hunting Collecting Fisheries by-catch Trade Bioaccumulation Increasing chemical concentration in first organism in a food chain Biomagnification ex: Increasing chemical concentration in successive trophic levels DDT passed up the food web Note: not just pesticides! Other pollutants similarly harmful Millennium Ecosystem Assessment A few of the Key Messages: The benefits of biodiversity go beyond the material, also: security, resiliency, social, health, freedom of choices and actions The past 50 years have seen the largest changes in biodiversity in human history Although in the past people have benefitted from converting natural ecosystems to human-dominated ecosystems, these are resulting in greater and greater costs By far the most important cause of biodiversity loss is habitat change, followed by climate change, invasives, overexploitation, and pollution. In preventing biodiversity loss, short-term trargets are not sufficient for success: need more holistic approach. Blue whale Cause: Whaling Current moratorium Millennium Ecosystem Assessment