What is the Holocene?

Transcription

1 What is the Holocene? The last 11,800 years Oxygen Isotope Stage 1 (warm interglacial) Clear indications of human impact on the environment - Development of agriculture/urbanisation

2 What is the Quaternary? Since at least the nineteenth century, different groups of geologists have used conflicting terms to describe the recent past. Some simply describe the past 23 million years as the Neogene period. But others invoke an extra period the Quaternary which follows the Neogene and began around 2 million years ago. The last million years

3 The lead up to the Holocene

4 Climate and the Holocene

5 Abrupt Climate Change Events

6 Case Studies. Kuk Swamp Lake Euramoo Bega Swamp

7 Case Study. Tropical Rain Forest of Northern Australia The rainforest vegetation includes mixtures with sclerophyll tree species that occur as emergent and co-dominant species in the canopy. Fringing the rainforests are areas of tall, open forest and tall, medium and low woodland. The palaeoecological record is from Lake Euramoo, a small crater lake at 730 masl near the boundary of sub-montane rainforest and schlerophyll woodland.

8 Tropical Rain Forest of Northern Australia Lake Euramoo Age (cal yr BP) RAINFOREST GYMNOSPERMS RAINFOREST ANGIOSPERMS SCHLEROPHYLL WOODLAND HERBS INTRODUCED Charcoal density Rate of Change Palaeodiversity Zones Depth m 16 0 Eu Eu Eu Eu-2 Eu ka: Cold/Dry Schlerophyll Woodland Low turnover

9 Tropical Rain Forest of Northern Australia Lake Euramoo Age (cal yr BP) RAINFOREST GYMNOSPERMS RAINFOREST ANGIOSPERMS SCHLEROPHYLL WOODLAND HERBS INTRODUCED Charcoal density Rate of Change Palaeodiversity Zones Depth m 16 0 Eu Eu Eu-3 Eu-2 Eu ka: Mosiac Schlerophyll Woodland- Sub-Montane Rain Forest Punctuated high turnover episodes

10 Tropical Rain Forest of Northern Australia Lake Euramoo Age (cal yr BP) RAINFOREST GYMNOSPERMS RAINFOREST ANGIOSPERMS SCHLEROPHYLL WOODLAND HERBS INTRODUCED Charcoal density Rate of Change Palaeodiversity Zones Depth m 16 0 Eu Eu Eu-3 Eu-2 Eu ka: Warm Sub-Montane Rain Forest Very low turnover

11 Tropical Rain Forest of Northern Australia Lake Euramoo Age (cal yr BP) RAINFOREST GYMNOSPERMS RAINFOREST ANGIOSPERMS SCHLEROPHYLL WOODLAND HERBS INTRODUCED Charcoal density Rate of Change Palaeodiversity Zones Depth m 16 0 Eu Eu ka: Cool/Dry Sub-Montane Rain Forest with increasing turnover Loss of long-lived trees (eg Agathis) Eu Eu-2 Eu-1

12 Tropical Rain Forest of Northern Australia Lake Euramoo Age (cal yr BP) RAINFOREST GYMNOSPERMS RAINFOREST ANGIOSPERMS SCHLEROPHYLL WOODLAND HERBS INTRODUCED Charcoal density Rate of Change Palaeodiversity Zones Depth m Eu-5 Eu-4 Last 1 years: Cold/Dry Sub-Montane Rain Forest with High Turnover Invasion of exotic plants Eu Eu-2 Eu-1

13 Char coal (>5 µ m) Bega Sw amp m, Southern New South Wales Pod oca rpus Pomaderris Eucalyptus type 1 Eucalyp tus c f. pauciflora Eucalyp tus type 2 Acacia Callitris Casuarina Epacr is type Kunzea type L eptospermum Monolet e Fer n spores Blechnum Poaceae Tubulifl orae Age (years BP)

14 Implications of long-term increases in disturbance for rain forest ecosystems Increase disturbance frequency post 5000 yr BP higher turnover rates loss of large long-lived trees internal fragmentation alters species composition greater opportunity for invasion by fast growing plants (eg. gap-dependent species, weeds and lianas) Phillips et al. (02) Nature 418,

15 Origins of Agriculture Centres of origin of food production Archaeological and palaeoecological studies have revealed at least 10 independent centres of food production. New Guinea has been considered a secondary centre, where agricultural development was derived from or triggered by the arrival rival of domesticates from Southeast Asia.

16 Two Hypotheses 1. DISPERSAL: : Domesticated plants (taro, bananas, sago, sugarcane) and animals (pig, chicken) were dispersed from Southeast Asia as part of the migration of Austronesian Austronesian speakers around 4000 yr BP into the Pacific and Indian Oceans.

17 Two Hypotheses 2. INDEPENDENT INVENTION: New Guinea was a primary centre for agricultural development and plant domestication prior to any known influence from Southeast Asia (prior to 4000 yr BP).

18 The Highland Valleys The highland valleys are found along the main cordillera of inland New Guinea between an altitude of m asl.. Intensive agriculture supports a population of over 3 million people there today. Kuk Swamp h

19 Archaeological Evidence for Agriculture: Kuk Swamp Plant exploitation and some cultivation occurred on the wetland margin at 100 cal BP (Phase I) Mounding cultivation began by 7000 cal BP (Phase II) Ditched cultivation began by 4350 cal yr BP (Phase III). Phase I II III IV V&VI Cal kyr BP

20 Anthropogenic Indicators in New Guinea

21 Kuk Swamp Pollen Record: LGM-Present Calibrated Radiocarbon Date BP (x1000) Musaceae (% phytolith sum) Ensete Eumusa Musa ingens >15 5 Pollen and Spores (% total sum) Black clay Phase 3 Phase 2 Grey-brown clay Phase 1 Late Pleistocene Archaeostratigraphy peat

22 Non-Synchronous Forest Clearance in the Mid-Late Holocene An increased focus on wetland cultivation during the mid-late Holocene led to rapid clearance of forests, particularly swamp forest environments. nments. Swamp Arboreal Pollen Myrtaceae Baliem Telefomin Tari % Age (10 yr B.P.) Age (10 yr B.P.) 0 Kainantu Nurenk 8ka 7ka 3ka 7ka 4ka 2ka h h h hh h Forest decline is not synchronous across the highlands.

23 Conclusions Evidence for agriculture by at least 7000 cal yr BP (and possibly y as early as 7800 cal yr BP) is consistent with two indicators for anthropogenic activity (i) appearance in fossil record of cultivated species, and (ii) non-synchronous forest loss across the highlands. At Kuk Swamp clearance of lower montane rain forests commenced in the Early Holocene with modification to grassland and cultivation of bananas by 7000 cal BP. Agriculture arose independently in New Guinea between cal BP, more than 3000 years before any known influence from Southeast Asia.