PEOPLE 3000 - PalEOclimate and the PeopLing of the Earth



By integrating archaeological data, paleoecological data and dynamic modeling, PEOPLE 3000 aims to explain long-term patterns of growth in the consumption of energy in social-ecological systems and the tipping points of these systems within the contexts of changing climates and environments over the last 3000 years.


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Watch presentations from several working group members on YouTube.


- Developing high-precision records of paleoclimate, human population and energy consumption over the last 3000 years.
- Comparing changes in population, energy consumption and social complexity from region to region.
- Identifying regionally comparative patterns in order to explain relationships between variation in ecosystem change, subsistence and social diversity, and the severity of social-ecological reorganization.


Jacob Freeman (Utah State University, USA)
Macarena Cárdenas (Earthwatch, UK)
Adolfo Gil (CONICET/IANIGLA-UTN FRSR, Argentina)
Claudio Latorre (Pontificia Universidad Catolica de Chile)
Erick Robinson (University of Wyoming, USA)
Molly Cannon (Utah State University, USA)


Aug 2017
Aug 2021

The prehistory of human-environment interactions is an important and under used source of knowledge critical for meeting the challenges of a globalizing planet confronting population growth and climate change.

The PEOPLE 3000 working group combines archaeological and paleoecological case studies with mathematical modeling to investigate how co-evolving human societies and ecosystems can successfully cope with the interrelated forces of population growth, increasing social complexity and climate change, and, sometimes, why societies fail to cope with these interrelated forces and reorganize.

Our research contributes to understanding why some coupled social-ecological systems display gradual change, while others experience tipping points and rapid change leading to growth or decline and even collapse.

People and ecosystems

Recent analyses of paleoenvironmental and archaeological records demonstrate clear evidence for dramatic demographic and socio-ecological changes in small-scale to medium scale societies over the past 3000 years.

First, about 3000 years ago human populations and energy consumption in many regions of the globe began to grow. This growth was fastest from 2000 to 800 years BP and was coincident with increases in social complexity.

Second, between 800 and 400 years BP, in many regions, population and energy consumption declined and social-political institutions reorganized. This decline is coincident with the transition of the global climate system between 700 and 550 BP to the Little Ice Age Period (700-100 BP), and the magnitude of decline in population, energy consumption and social reorganization is variable from region-to-region.

These patterns beg a simple question: Why are some reorganizations of social-ecological systems (SES) more severe than others? In particular, as the global climate system transitioned to the Little Ice Age Period, why might this climate change have had a more severe effect (if it did) on the organization of SES in some places and less in others?

people3000 concept

Conceptual diagram of the components of our project. PEOPLE 3000 combines data from archaeological and paleoecological case studies. We combine these data by building formal models of social-ecological systems to study robustness-fragility tradeoffs, the long-term population ecology of humans and the effects of diversity on the ability of human societies cope with social, ecological and climate change.

About the working group

The motivation for PEOPLE 3000 stems from a PAGES workshop held at Utah State University in November 2016. The working group sits in the middle of the PAGES triangle, integrating knowledge from ecosystem ecology, paleoecology and the social sciences. By investigating the complex nexus between climate, ecosystem structure and human practices, we are increasing our understanding of social-ecological systems.

We are especially interested in understanding the formation of multiple equilibria separated by "tipping points" in social-ecological systems. The multiple reorganizations in social, political and economic practices, as well as population densities, observed after 800 years ago may be the result of many regional systems experiencing variance induced critical transitions from a high human population equilibrium supported by more complex social institutions to a lower population equilibrium.

Sustainability is, in a sense, the ability of SES to move from one equilibrium to another without the loss of critical ecosystem functions, adaptive capacity and declines in well-being among human populations. By comparing and modeling how climate interacts with human population ecology, we can develop a deeper understanding of tradeoffs inherent in the adaptive dynamics of social-ecological systems. In turn, this should help us think about sustainability as a dynamic concept that changes as social and ecological systems co-evolve.

> Find out more about the working group members (YouTube videos)

Planned timeline

Year 1: August 2017-July 2018
a. September 2017: Data synthesis for our five initial case studies.
b. October 2017: Apply for expansion workshop funding to various. Submit a concept paper that compares our five initial case studies to a journal such as Nature Communications.
c. November 2017: Submit Coupled-Human Natural Systems NSF proposal.
d. February 2018: Workshop to expand on our initial case studies.

Year 2: August 2018-July 2019
a. October 2018: Data synthesis and analysis for new case studies.
b. March 2019: Submit a concept paper that compares new compiled case studies to a journal such as PNAS.
c. July 2019: Submit a session for INQUA (Ireland).

Year 3: August 2019-July 2021
a. August 2019: Submit a discussion paper about the concept of dynamic sustainability on the basis of a comparative analysis of initial and new case studies. Proposed journals: The Anthropocene or Earth’s Future.
b. January 2020: Gear-up for a second round of expansion to include more case studies.

Learn more and participate

Subscribe to the PEOPLE 3000 mailing list here.

> Find out more about the working group members (YouTube videos)

Know a case study that fits with this project? Get in touch! 

Read more about the group on its external website.