planetary boundaries for a blue planet (marine lecture 5) Flashcards
1
Q
What is the planetary boundaries concept?
A
- 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
2
Q
What was Holocene stability?
A
- 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
3
Q
What is the Anthropocene?
A
- fossil fuel reliance and industrial agriculture disrupt this stability
- push earth out of holocene
- abrupt irreversible environmental changes
4
Q
What are the planetary boundaries?
A
- 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
5
Q
How was the planetary boundary framework refined?
A
- 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)
6
Q
What are the planetary boundaries for a blue planet? Why is a marine perspective needed?
A
- 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
7
Q
How should blue planetary boundaries be approached?
A
- build on existing (Rockstrom, Steffen) + proposed boundaries
- integrate processes/data/concepts applicable in marine systems
8
Q
Why are blue planet boundaries important?
- land system change
A
- 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
9
Q
Why are blue planet boundaries important?
- carbon sequestration
A
- 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
10
Q
Why are blue planet boundaries important?
- albedo
A
- difference between boreal forest (low) and grassland (high) albedo similar between that of open ocean (low) and sea ice (high)
11
Q
Examples of how blue planet boundaries could be approached:
- marine habitat change
A
- 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
12
Q
Examples of how blue planet boundaries could be approached:
- biogeochemical flows
A
- 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
13
Q
What is biosphere integrity/the biosphere integrity index (BII)?
A
- 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
14
Q
Could there be a marine biosphere integrity index?
A
- 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
15
Q
How to integrate marine functional diversity?
A
- 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
