Orange County NC Website
Browse       Search
RESEARCH ( RESEARCHARTICLE <br />Table 1. The updated control variables and their current values, along with the proposed boundaries and zones of uncertainty, for all nine planetary <br />boundaries. In the first column, the name for the Earth - system process used in the original PB publication (R2009, reference 1) is given for comparison. <br />Earth - system <br />process <br />Climate <br />change <br />(R2009: <br />same) <br />Change in <br />biosphere <br />integrity <br />(R2009: <br />Rate of <br />biodiversity <br />loss) <br />Stratospheric <br />ozone <br />depletion <br />(R2009: same) <br />Ocean <br />acidification <br />(R2009: <br />same) <br />Biogeochemical <br />flows: (P and <br />N cycles) <br />(R2009: <br />Biogeochemical <br />flows: (interference <br />with P and N <br />cycles)) <br />Control <br />variable(s) <br />Planetary boundary <br />(zone of uncertainty) <br />Atmospheric CO2 350 ppm CO2 (350 -450 ppm) <br />concentration, ppm <br />Energy imbalance +1.0 W m -2 ( +1.0 -1.5 W m -2) <br />at top -of <br />atmosphere, W m -2 <br />Genetic diversity: < 10 E /MSY (10 -100 E /MSY) <br />Extinction rate but with an aspirational goal of <br />ca. 1 E /MSY (the background <br />rate of extinction loss). E /MSY = <br />extinctions per million species -years <br />Functional diversity: <br />Biodiversity <br />Intactness Index (BII) <br />Note: These are <br />interim control <br />variables until more <br />appropriate ones are <br />developed <br />Stratospheric 03 <br />concentration, DU <br />Carbonate ion <br />concentration, <br />average global <br />surface ocean <br />saturation state with <br />respect to aragonite <br />(�2arag) <br />P Global: P flow <br />from freshwater <br />systems into the <br />ocean <br />P Regional: P flow <br />from fertilizers to <br />erodible soils <br />N Global: Industrial <br />and intentional <br />biological fixation <br />of N <br />Maintain BII at 90% (90 -30 %) <br />or above, assessed <br />geographically by biomes /large <br />regional areas (e.g. southern <br />Africa), major marine <br />ecosystems (e.g., coral reefs) or <br />by large functional groups <br /><5% reduction from pre- <br />industrial level of 290 DU <br />(5 % -10 %), assessed by <br />latitude <br />> > -80% of the pre - industrial <br />aragonite saturation state of <br />mean surface ocean, including <br />natural diel and seasonal <br />variability ( > -80 %- > -70 %) <br />11TgPyr 1(11- 100TgPyr ) <br />6.2 Tg yr 1 mined and applied to <br />erodible (agricultural) soils <br />(6.2 -11.2 Tg yr 1). Boundary is a <br />global average but regional <br />distribution is critical for <br />impacts. <br />62 Tg N yr 1 (62 -82 Tg N yr 1). <br />Boundary acts as a global <br />'valve' limiting introduction of <br />new reactive N to Earth System, <br />but regional distribution of <br />fertilizer N is critical for <br />impacts. <br />Current value of <br />control variable <br />398.5 ppm CO2 <br />2.3 W m -2 <br />(1.1 -3.3 W m -2) <br />100 -1000 E /MSY <br />84 %, applied to <br />southern Africa <br />only <br />Only transgressed <br />over Antarctica in <br />Austral spring <br />(-200 DU) <br />-84% of the <br />pre - industrial <br />aragonite <br />saturation state <br />- 22TgPyr 1 <br />- 14TgPyr1 <br />-150 Tg N yr 1 <br />1259555 -4 13 FEBRUARY 2015 • VOL 347 ISSUE 6223 sciencemag.org SCIENCE <br />