BS945 Lecture 2 Anthropocene 2024 (PDF)

Overview The ‘Anthropocene’ Human impacts on the planetary system Impact of human technologies on the environment Synthetic chemicals Human population growth November 2024 https://www.worldometers.info/world-population/ Historic size of human p...

Overview The ‘Anthropocene’ Human impacts on the planetary system Impact of human technologies on the environment Synthetic chemicals Human population growth November 2024 https://www.worldometers.info/world-population/ Historic size of human population http://esa.un.org/unpd/wpp2008/Fig_1.htm Anthropocene Age in which human activity has been the dominant influence on climate and the environment Rockstrom et al. 2009 Nature 461, 473-475. Critical processes which maintain a stable and resilient planet Richardson et al. 2023 Science Advances 9. 37. Boundary: 350 ppm CO2 in the atmosphere 450 ppm is high risk Equivalent to 1-2 oC temperature rise 427 ppm in June 2024 Surface air temperature changes Hansen et al 2012 PNAS E2415-E2423  Global warming https://showyourstripes.info  IPCC special report Impacts of a 1.5oC rise World heading for 3oC rise 1.5oC rise by 2030 https://www.bbc.co.uk/news/science-environment-45775309 Impacts of climate change Boundaries: Biosphere integrity Genetic: biodiversity loss Functional: 10 % loss of net primary productivity (relative to Holocene: 59 Gt C Y) Biodiversity loss  Biodiversity loss Rate of species extinctions is 10-100 higher than the av. rate over the last 10M years Current extinction rate is >100 extinctions per million species years Of 8 million plant and animal species 1 million are threatened with extinction 10 % of animal and plant biodiversity may have been lost in the last 150 years Richardson et al. 2023 Science Advances 9, 37  Loss in biodiversity Rate of mammal extinction: 2 per 10,000 species per 100 yr Current rates 100 X background  Biodiversity Loss 42 % decline since 1994 Number of wild animals, birds and fish on earth has halved since 1970s https://ourworldindata.org/wild-mammals-birds-biomass Biodiversity loss Protect 30 % of land and sea area UK Species introductions  Harlequin Ladybird Harmonia axyridis Native to China Used for biocontrol Pest control of aphids and mealybugs since 1916 Brown et al 2011 BioControl 56, 623-641 Harlequin ladybird distribution Roy and Brown 2015 Ecol Ent 40, 336-348 Boundaries: Biogeochemical flows Phosphorus Current loss: 22 Tg y Agricultural use: 17.5 Tg y Nitrogen Boundary: use of 62 Tg y Current use: 190 Tg y N fertiliser N availability limits crop growth and yield Fertiliser addition increases yield  Human fixation of N Haber-Bosch process (1909) N2 from air fixed to NH3 using iron catalyst NH3 oxidised to NO3 for use as fertiliser Current industrial fixation of N as fertiliser is 80 Tg yr; may reach 135 Tg yr by 2030 1-2 % of the worlds total energy consumption is spent making N fertiliser The nitrogen cycle Human population and N use European nitrogen fluxes Sutton and van Grinsven (2011) European nitrogen Assessment: Summary for Policy Makers. Cambridge University Press. Eutrophication  Marine dead zones 405 dead zones identified by 2008; 49 in 1960s Baltic sea is the largest: upto 9000 miles2 Gulf of Mexico dead zone is 8500 miles2 http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ ocean-color/dead_zones.shtml http://www.scientificamerican.com/article.cfm?id=oceanic-dead- zones-spread Human induced trace gas emissions Nitrous oxide Concentrations rose from 270 ppbv in 1750 to >320 ppbv currently Long atmospheric life span (120 years) 310 more powerful as a greenhouse gas than CO2 (on a per molecule basis)  Nitrogen driven ecological change % of species number or similarity to a non-impacted ecosystem Boundaries: Freshwater Change Wet or dry deviations Blue- surface and groundwater 18 % Green- plant available soil water 16 %  Water Humanity uses >50 % of planet’s accessible fresh water 70 % of human use is for agriculture Flow of two thirds of planet’s rivers is regulated; the world has 36000 dams; in US only 2 % of rivers run unimpeded 6 % of earth’s river flow is lost by human induced evaporation Use of groundwater in arid regions is non-renewable (75 % of water used in Saudi Arabian is fossil water) Aral sea  Aral sea 67500 Km2 to 9450 Km2 Boundary: Land System Change 85/ 50 /85 retention of boreal/ temperate/ tropical forest Agricultural intensification  How much of the land’s surface is managed for farming? Biome Land area Cropland as Pasture as Total (million km2) % biome area % biome area Tropical forest 22.6 15.0 12.9 27.9 Temperate forest 9.6 25.5 14.8 40.3 Boreal forest 8.2 1.6 1.8 3.4 Savanna 19.2 15.7 33.8 49.5 Grassland 14.3 19.2 50.7 69.9 Shrubland 17.9 10.8 39.2 50.0 Tundra 7.0 0.6 13.1 13.7 Desert 15.3 0.9 7.9 8.8 Polar regions 1.2 0.1 1.7 1.8 >1/3 of the world’s ice-free area is used for agriculture  Global Land Outlook, UN Over last 20 years, 20 % earths vegetated surface has declined in productivity 1.3 billion people ‘trapped’ on degrading land  Land degradation Extent, causes and consequences of degradation: Erosion Salinisation Desertification Global soil erosion losses Li and Fang (2016) Earth Sci Rev 163, 94-117 1 ha = 100 m square Boundary: Novel entities Release into the earth system of 0 % untested synthetics Discuss types of materials novel entities represent How have your activities today contributed to release of these? Boundary: Novel entities Release into the earth system of 0 % untested synthetics Synthetic chemicals  Published 1962 Led to creation of US EPA  Synthetic chemicals DDT led to decline of birds of prey globally In UK Peregrine falcon populations had declined by 80 % by 1963 Recovery took until 1990s Plastic waste https://www.statista.com/ chart/32385/global-plastic- waste-production-by- application/ 4.8 - 12.7 mt plastic / yr enters the ocean Jambeck et al. 2015 Science 347, 761-771 https://ourworldindata.org/plastic-pollution  Stratospheric ozone depletion Chlorofluorocarbons used since 1920s as refridgerants and aerosol propellants Persist for 50-100 years Evidence in 1974 that they accumulate in stratosphere and destroy O3 in catalytic cycles Banned in 1989  Stratospheric ozone depletion UV light splits O2 to 2O which react with O2 to give O3 90 % of O3 is in the stratosphere, rest in troposphere O3 layer absorbs UV light  Effect of stratospheric ozone depletion on human health http://maps.grida.no/go/collection/vital-ozone-graphics  Recovery to pre-1980s levels by 2075 But….