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Sustainable Yield
 

Sustainable Yield

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Sustainable Yield Sustainable Yield Presentation Transcript

  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital 3.2.7: Sustainable Yield
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The extent to which a given interaction with the environment exploits and utilizes the natural income without causing long term deterioration to the natural capital. For example, a system of harvesting renewable resources at a rate that will be replaced by natural growth might be considered to demonstrate sustainability. A Long Definition
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital 'development which meets the needs of the present without compromising the ability of future generations to meet their own needs' A Better Definition
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Sustainable Yield Sustainable yield (SY) may be calculated as the rate of increase in natural capital Or The idea that a “crop” can be taken from an ecosystem in a way that leaves the ecosystem viable for the future
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Sustainable Yield total biomass total biomass SY = @ time t + 1 - @ time t energy energy OR SY = (annual growth and recruitment) - (annual death and emigration) The model works on the idea that as long as there are more new members of a population at the end of the year than at the beging it is possible to exploit the extra without harming the population
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 13.0 6.5 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 13.0 Population in 6.5 the first year 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 13.0 Population in Population in the second 6.5 the first year year 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 13.0 Population in Population in the second 6.5 the first year year 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 “surplus” 13.0 Population in Population in the second 6.5 the first year year 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The theory 26.0 19.5 sustainable “surplus” yield? 13.0 Population in Population in the second 6.5 the first year year 0 2007 2008
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Assumptions of Sustainable Yield models There is enough data to know the populations real size and growth rate That the population has an even age structure Harvesting individuals is random and does not disproportionately affect the breeding stock That the population is not affected by natural fluctuations e.g. outbreaks of disease
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Problems with assumptions In a stock where most individuals are breeding age and grow to maturity is slow Year 1 Year 2 Year 3 immature immature breeding stock breeding breeding stock stock immature old and diseased old and old and diseased diseased Stock harvested
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Problems with assumptions The a lot of immature stock can make the population appear to be in surplus Year 1 Year 2 Year 3 immature immature breeding stock breeding breeding stock stock immature old and diseased old and old and diseased diseased Stock harvested
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Problems with assumptions The old continue to die at the same rate as breeding stock become old Year 1 Year 2 Year 3 immature immature breeding stock breeding breeding stock stock immature old and diseased old and old and diseased diseased Stock harvested
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Problems with assumptions So when harvesting starts it is the breeding stock that is removed Year 1 Year 2 Year 3 immature immature breeding stock breeding breeding stock stock immature old and diseased old and old and diseased diseased Stock harvested
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Problems with assumptions And the immature do not grow fast enough to replace the breeding stock lost Year 1 Year 2 Year 3 immature immature breeding stock breeding breeding stock stock immature old and diseased old and old and diseased diseased Stock harvested
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital The Story of the Orange Roughy
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy: The ecology Habitat: cool deep waters Slow-growing, very long-lived fish, up to 150 years Feeds on prawns, fish and squid Do not breed until about 25 - 30 years old Lay about 10% less eggs than most fish species
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy: Australia Found in deep water of Southern Australia Large scale fishing started in the 1990’s Within a decade shoals reduced to 10% of original size Australian Government introduced quotas
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy: Australia 30 years ago found large numbers in deep water of Southern Australia Large scale fishing started in the 1990’s Within a decade shoals reduced to 10% of original size Australian Government introduced quotas
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy: Australia 30 years ago found large numbers in deep water of Southern Australia Large scale fishing started in the 1990’s Within a decade shoals reduced to 10% of original size A haul of orange roughy. Photo AFMA Australian Government introduced quotas
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Catch (tonnes) Year
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy Catch: Austrailian waters 1990 - 2001 90,000 80,000 Catch (tonnes) 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year
  • Topic 3: Human population, carrying capacity and resource use 3.2 : Resources Natural Capital Orange Roughy: Declining catches Early population counts were based on fishing records No account taken of low reproductive rate and long time to maturity Management plans have not stopped the decline Since discovered that Orange Roughy reproduction is also spasmodic and irregular