planetary boundaries for a blue planet (marine lecture 5) Flashcards
What is the planetary boundaries concept?
- human civilisation developed in unusually environmentally stable Holocene period
- since the industrial revolution = Anthropocene
- human activities may push Earth out of stable Holocene state w detrimental/catastrophic effects for parts of world
What was Holocene stability?
- under slow, natural environmental change w earth’s regulatory capacity maintaining relatively stable conditions
- temperature, freshwater availability & geochemical fluxes stayed w/i a relatively narrow range
- feedback processes maintained global/regional stability
What is the Anthropocene?
- fossil fuel reliance and industrial agriculture disrupt this stability
- push earth out of holocene
- abrupt irreversible environmental changes
What are the planetary boundaries?
- a safe operating space
- must live w/i to allow regulatory biophysical processes to persist
- if thresholds exceeded important subsystems may shift into new state
How was the planetary boundary framework refined?
- discussed widely in policy, government, business sectors
- key platform informing global sustainability efforts
refined to:
- account for regional level heterogeneity
- update quantification of planetary boundaries
- identify the the core boundaries at global & regional levels
(Steffen et al., 2015)
What are the planetary boundaries for a blue planet? Why is a marine perspective needed?
- most pb research focused on terrestrial systems
- but marine systems key to earth system functioning and societal wellbeing
marine ecosystems:
- big
- differ structurally & biologically from terrestrial ecosystems
- under increasing pressure
- critical to human beings, especially in poor countries where fisheries provide most protein
How should blue planetary boundaries be approached?
- build on existing (Rockstrom, Steffen) + proposed boundaries
- integrate processes/data/concepts applicable in marine systems
Why are blue planet boundaries important?
- land system change
- vegetative cover mediates climate (C storage, moisture transfer, surface energy transfer)
- measured habitat change
- e.g. forest to cropland = change in C sequestration, albedo, evapotranspiration
marine biomes influence climate directly via similar processes to terrestrial biomes:
- C sequestration by coastal vegetation
- albedo changes (melting sea ice)
- ocean-atmosphere coupling may counteract some terrestrial processes
Why are blue planet boundaries important?
- carbon sequestration
- coastal habitats have v high C sequestration (salt marshes 50+x higher than tropical rainforests)
- degradation of mangroves, sea grasses, coastal marshes etc driving emissions of similar order to deforestation despite 7x less area
Why are blue planet boundaries important?
- albedo
- difference between boreal forest (low) and grassland (high) albedo similar between that of open ocean (low) and sea ice (high)
Examples of how blue planet boundaries could be approached:
- marine habitat change
- change existing control variables
- e.g. relative ice cover as equivalent to remaining forest cover
- add sub-boundaries for loss of marine habitats
- e.g. 3D structural complexity, area of undisturbed sea bed
Examples of how blue planet boundaries could be approached:
- biogeochemical flows
- 2 sub-boundaries: N & P
- we aggregate regional effects in terrestrial and freshwater systems but only globally for marine
- eutrophication is a major threat to coastal marine ecosystems
- should measure regional effects in marine systems
- consider other important marine nutrients (Fe & Si)
- should consider top down biogeochemical impacts like fisheries ad well as bottom up enrichment
- marine biogeochemical regimes vary with depth & through space
- large differences in biogeochemical cycling, primary productivity and marine foodwebs
- different marine ecosystems have different vulnerabilities to increased nutrient loading
What is biosphere integrity/the biosphere integrity index (BII)?
- core planetary boundary central to earth system state
- persistence - evolutionary history
- functioning - functioning diversity
- measured by biosphere integrity index
- the biosphere integrity index is the proportion of species remaining as compared with primary vegetation
Could there be a marine biosphere integrity index?
- feasibly BII could be developed for marine sites but lack of “control” sites data
- functional diversity well established in marine ecosystems measured with biological traits
- trait based measures could enhance current biosphere integrity as are more closely linked to ecosystem functioning than measures of richness
How to integrate marine functional diversity?
- build on extensive work on marine system functional diversity
- develop indicators of ecosystem state
- e.g. size-based indicators for fisheries monitoring
- apply accross systems for more holistic estimate of biosphere integrity
What is Human Appropriated Net Primary Productivity (HANPP)?
- HANPP is the amount of NPP appropriated by humans
- directly or via crops/livestock
- proposed as additional planetary boundary
- quantifies effect anthropogenic changes in productivity and harvest on ecological biomass flows
Why/how to integrate marine HANPP?
- 50% global production is marine
- similar proportions NPP flows into shelf sea fisheries as is appropriated by humans on land
- oceans comparable to land as C sink
- harmonise integration of marine and land measures of productivity - new production v biomass accumulation
What are the critiques of the planetary boundaries concept?
- no evidence for/theoretical reason for extinction rate tipping types
- allowing gradual change and not just threshold like tipping points make boundaries arbitrary
- limit arbitrary even if robust estimates for biodiversity change were made
- lacks clear definitions/too many contradictions
- no unit specifications
- no operational definitions so hard to apply practically
What are the potential dangers of the planetary boundaries concept?
- no operational definition of ‘safe operating space’
- encourages idea human actions used to be environmentally benign/allowed recovery
- idea that if planet isn’t literally collapsing yet we can continue to deplete it
What are alternatives to the planetary boundaries concept?
address how biodiversity loss affects the different facets of ecosystem change:
• resilience (how fast systems recover)
• resistance (how much they change)
• variability (how much they fluctuate over time)
• persistence (how long they persist)
well-defined, have units, can
be monitored over time, can inform management
