BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:When did humans start to influence rivers? A contribution to the A nthropocene debate - Professor Martin Gibling\, Department of Earth and En vironmental Sciences\, Dalhousie University DTSTART:20230213T180000Z DTEND:20230213T190000Z UID:TALK196414@talks.cam.ac.uk CONTACT:Buck Blake DESCRIPTION:The term Anthropocene\, first used informally by Paul Crutzen and Eugene Stoermer in 2000\,\nhas been widely adopted to indicate how pro foundly humans have modified the Earth system.\nA proposal is being discus sed to define a geological Anthropocene Epoch\, commencing around\n1950. T hrough the 20th century\, the proliferation of big dams\, irrigation proje cts and\nindustrial pollutants have profoundly affected rivers worldwide. However\, humans have\nalways lived along rivers and began to modify them much earlier in the Quaternary\, as shown\nby evidence from sedimentology and archaeology.\n\nThe use of fire\, perhaps by 1.6 Ma in Africa\, may ha ve been the first anthropogenic influence\non river landscapes. Indigenous use of fire in hunting may have affected Australian vegetation\nby 45\,00 0 years ago (45 ka)\, although this is controversial. Hunter-gatherers col lected and\nprocessed grain on floodplains and uplands before 30 ka\, but the rise of agriculture and\nassociated deforestation greatly enhanced sed iment runoff\, creating river “legacy sediments”\nthat date back to ne arly 8 ka in New Guinea. Preceded by cultivation of wild cereal species\,\ ndomestication of wheat\, barley and other founder crops after about 10.7 ka led to organised\nagriculture on river plains across the Near East by 9 .8 ka. Rice was domesticated by 9 ka in\nChina\, with widespread ricefield irrigation after 7 ka\, and maize and squash were cultivated in\nMexico b y about 9 ka. Animal husbandry affected river landscapes through grazing\, transport\nroutes along rivers\, and ploughing. Cattle\, sheep\, goats an d pigs were domesticated by 10 ka\,\nyaks by 7 ka\, donkeys and horses aft er 7 ka\, and water buffalo by 5 ka.\n\nSettled communities along rivers g o back to at least 14 ka in the Near East\, with Jericho\nfounded at a spr ing around 10 ka. Large riverside cities developed after about 7.4 ka in t he empires of\nMesopotamia\, Egypt\, and the Indus Valley. The growth of c ities was associated with urban\nsupply systems and irrigation canals\, so on leading to salination of floodplain soils in\nMesopotamia. By 3 ka\, pr inciples of groundwater extraction were well understood\, bringing\nsubsur face water to fields. Floodplain clays were worked for pottery after aroun d 20 ka\, for ochre by\naround 15 ka\, and for bricks by around 9.5 ka. Ri ver boats and infrastructure were in use early in the\nHolocene\, and papy rus has been harvested from rivers since at least 5 ka.\n\nFollowing early brushwood and earth dams\, the Egyptian Pharaohs built the first stone-fa ced\ndam in 4.5 ka\, and the Romans constructed 45 large dams in the Middl e East. Chinese\nemperors engaged in enormous engineering schemes along th e Yellow River over the past\nseveral thousand years. Water mills and pond s affected river sediments and depleted fish\nstocks across Europe in the Middle Ages.\n\nIn summary\, anthropogenic activities influenced rivers in many ways from the latest\nPleistocene onward\, intensifying through the Holocene. Such profound modifications were\ndiachronous and left their mar k not only in the geological record but also on biological\ncommunities an d human cultures. It seems appropriate to represent a transformative chang e\nover this long period as an Anthropocene Event (Gibbard et al.\, 2021)\ , allowing the term to be\napplied to a range of disciplines and societal applications.\n\nGibbard\, P.L. et al.\, 2021\, A practical solution: the Anthropocene is a geological event\, not a\nformal epoch. Episodes\, Nov. 15\, 2021. LOCATION:Tilley Lecture Theater\, Department of Earth Sciences END:VEVENT END:VCALENDAR