Anthromes, CO2 and Terrestrial Carbon – Session 4: Carbon in Indigenous and pre-industrial anthromes
Authors: Fletcher Michael-Shawn , Levis Carolina , Kaplan Jed , Roberts Patrick 
Published: March 2023

8.30 – 8.35: Welcome to the day

8.35 – 9.05: Aboriginal cultural burning, catastrophic fires, and the carbon cycle: ancient techniques for modern problems, Michael-Shawn Fletcher*

9.05 – 9.35: Carbon in indigenous and pre-industrial anthromes: An overview of stocks and processes, Jed Kaplan

9.35 – 10.05: Legacies of long-term cumulative activities of Indigenous peoples in Amazonian forest composition and dynamics, Carolina Levis (presenting remotely)

10.05 – 10.35: Pre-industrial land use transitions in the tropics and their multi-scalar ramifications for the carbon cycle , Patrick Roberts (presenting remotely)

Aboriginal cultural burning, catastrophic fires, and the carbon cycle: ancient techniques for modern problems

The 2019/2020 Black Summer bushfires on the eastern seaboard of Australia heralded a worrying shift in Australian fire regimes toward more frequent, larger, and hotter bushfires. Not only did these fires have significant negative ecological, cultural, and economic impacts, they resulted in a massive input of carbon into the atmosphere. Moreover, fires of this type and magnitude reduce the carbon storage capacity of temperate forests in southeast Australia for subsequent decades. The spatial extent of the Black Summer bushfires is unprecedented in the historical and geological record. While these fires represent a clear change in the size and intensity of fire in the temperate forests of Southeast Australia, they are the culmination of a series of catastrophic bushfires in this region that began in the 1850s that is characterised by a ramping up in frequency, size, and intensity over recent decades. While climate change is often cast as the key driver of the current bushfire crisis, palaeoecological data reveals that these fires began prior to the effects of climate change. Rather, a massive increase in flammable fuel loads occurred following the suppression and removal of Aboriginal care for Country with fire (known as cultural burning) following the British invasion of the continent that began in 1788 and continued through the 1800s. Here I will unpack the temporal sequence that has led to the current southeast Australian bushfire crisis using historical, palaeoecological and dendroecological data from across southeast Australia. I will elucidate the positive effects of an ethos that embraces fire (inherent within the Aboriginal world view) has in comparison with one that fears and fights fire (pervasive within European-derived world views). I will demonstrate how this shift in world views, coupled with an ignorance of how Aboriginal people have curated and cared for the Australian continent for tens of millennia, have produced the current bushfire crisis. I will demonstrate how cultural burning increases biodiversity, reduces catastrophic fires, and increases the amount and long-term security of carbon stored in these flammable temperate forest systems, reflecting a path out of the current unravelling of the continent environment.

Legacies of long-term cumulative activities of Indigenous peoples in Amazonian forest composition and dynamics

Indigenous peoples have occupied the Amazon basin for over 12,000 years. During this time, they have developed a profound knowledge of ecosystem management and forest ecology, which allowed them to create domesticated landscapes that are more productive, increasing their well-being. This presentation explores three intertwined forms of human modification of Amazonian forests: (1) earthworks, (2) Amazonian Dark Earths, and (3) cultural/domesticated forests. With earthmoving techniques, indigenous peoples created a wide variety of land structures with social, ceremonial, and defensive functions. Soils were modified and their fertility increased, expanding the distribution of nutrient-demanding plants. On and around these anthropogenic earthworks and soils, Indigenous communities have also managed hundreds of tree species, some of which show evidence of domestication, generating long-lasting changes in forest composition and dynamics. Plant species with greater utility have been selected, dispersed, and propagated while unwanted plants have been filtered out. This ancient interaction between Indigenous peoples and Amazonian forests implies that both are part of an ancient social-ecological system. By examining Amazonia as an Anthrome, we can offer a more realistic approach to understanding the biomes´ responses to climate change (including changes in the carbon cycles) and provide insights for guiding its sustainable future.

Carbon in indigenous and pre-industrial anthromes: An overview of stocks and processes

While many studies consider the vaguely defined “preindustrial era” as a period when anthropogenic influence on the global carbon cycle was minimal or non-existent, it is increasingly clear that millennia of land use before the Industrial Revolution caused major changes in the structure of terrestrial ecosystems. Here, I will give an overview of the diversity, spatial, and temporal expression of pre-industrial land use from the Last Glacial Maximum to the 19th century CE. Already in the late Pleistocene, Paleolithic hunter-gatherers’ use of fire caused major changes in forest cover and concomitant carbon stocks. With the advent of agriculture and pastoralism in the Holocene, deforestation, soil erosion, irrigation, and wetland manipulation further modified the amount of carbon in anthromes, in many places reducing, but in some augmenting, carbon stocks. The late-preindustrial world was already transformed by urbanization, global trade in commodities, and exploitation of landscapes for natural resources. In this presentation I will summarize the state of the art and review the major open questions and priorities for future research, especially moving beyond deforestation as the basic metric of past human influence on the environment.

Pre-industrial land use transitions in the tropics and their multi-scalar ramifications for the carbon cycle

Tropical forests are critical to the operation of many parts of the Earth System, including the carbon cycle. Given the role of these habitats as carbon sinks, combined deforestation, as well as changing fire regimes, has the potential to result in massive knock-on feedbacks for carbon in soils, ecosystems, and even the atmosphere. Although tropical forests were once considered to be blanks on the map of human history, growing multidisciplinary research is highlighting the ways in which pre-industrial societies occupied and managed these environments, with changing tropical land use patterns having the potential impact the Earth System long prior to the ‘Great Acceleration’. In this talk, I begin by highlighting the ways in which anthropogenic activities in tropical forests can impact the carbon cycle, on both local and global scales. I then move through time, from the Pleistocene to the Late Holocene, to explore the available evidence for significant transitions in anthropogenic land use in the tropics that might have had ramifications for terrestrial carbon and atmospheric CO2. I argue that by understanding the nature and tempo of these changes in the past, with a particular focus on the role of Indigenous communities in managing these habitats over millennia, we can develop more informed policies for the present and plan for a more just, sustainable future.