Periodic Reporting for period 4 - ALPHA (Assessing Legacies of Past Human Activities in Amazonia)
Reporting period: 2024-07-01 to 2024-12-31
1. What is the problem/issue being addressed?
The ALPHA (Assessing Legacies of Past Human Activities) project assesses how human activities and land use practices that have occurred over the past hundreds or thousands of years result in changes in that persist in the landscape and are manifested in modern forests. We are particularly focused on Amazonian rainforests, which were previously thought to be pristine and have a light human footprint prior to European arrival to the American continent in AD 1492. Archaeological data collected over the past several decades have shown that this is not the case. In some regions of Amazonia, indigenous people had complex and thriving societies. They were modifying soils, cultivating crops, burning forests, and changing the abundances of many types of plants. In some cases, these activities changed the landscape to the point that they are still evident in today's forests. These changes of the past may affect our understanding of modern ecology in one of the most biodiverse and culturally diverse places in the world.
2. Why is it important for society?
Amazonia holds approximately 15% of Earth's biodiversity and 17% of terrestrial carbon stocks. Because these forests are so vast and hold so much carbon, they are important components of global carbon models that predict how atmospheric CO2 levels will change in upcoming decades to centuries. These models current assume that Amazonian forests are in equilibrium and are not changing. However, past human activities and their legacies may result in forests that are still undergoing successional change, which could greatly affect carbon dynamics. The ALPHA project is looking to determine the successional stage of forests that are measured for biodiversity and carbon, so that researchers can understand whether or not these forests are in equilibrium or still undergoing successional change. This also makes the outcomes of the ALPHA project relevant for all of society.
The ALPHA project and its outcomes will also provide important data that can be used locally in Amazonia. Land rights of indigenous people are currently being questioned and threatened in many regions. Our data can show that indigenous people have lived on these lands for hundreds or thousands of years before Europeans came to the continent, and these types of data can be used in currently policy decisions regarding the land rights and ownership of indigenous people in certain areas.
3. What are the overall objectives?
The overall objectives of the ALPHA project are to generate data on the types, timing, duration, and locations of past human activities in Amazonian forests, and how/whether these activities leave signals that are still present in modern forests. We also aim to link these findings with current ecological and biogeographical patterns and processes documented in Amazonian forests over the last several decades. We aim to integrate past and modern ecology because what we observe and monitor today is usually dependent on processes that have occurred in the past, particularly in systems where individual trees live for hundreds of years - much longer than modern observations can see.
The ALPHA (Assessing Legacies of Past Human Activities) project assesses how human activities and land use practices that have occurred over the past hundreds or thousands of years result in changes in that persist in the landscape and are manifested in modern forests. We are particularly focused on Amazonian rainforests, which were previously thought to be pristine and have a light human footprint prior to European arrival to the American continent in AD 1492. Archaeological data collected over the past several decades have shown that this is not the case. In some regions of Amazonia, indigenous people had complex and thriving societies. They were modifying soils, cultivating crops, burning forests, and changing the abundances of many types of plants. In some cases, these activities changed the landscape to the point that they are still evident in today's forests. These changes of the past may affect our understanding of modern ecology in one of the most biodiverse and culturally diverse places in the world.
2. Why is it important for society?
Amazonia holds approximately 15% of Earth's biodiversity and 17% of terrestrial carbon stocks. Because these forests are so vast and hold so much carbon, they are important components of global carbon models that predict how atmospheric CO2 levels will change in upcoming decades to centuries. These models current assume that Amazonian forests are in equilibrium and are not changing. However, past human activities and their legacies may result in forests that are still undergoing successional change, which could greatly affect carbon dynamics. The ALPHA project is looking to determine the successional stage of forests that are measured for biodiversity and carbon, so that researchers can understand whether or not these forests are in equilibrium or still undergoing successional change. This also makes the outcomes of the ALPHA project relevant for all of society.
The ALPHA project and its outcomes will also provide important data that can be used locally in Amazonia. Land rights of indigenous people are currently being questioned and threatened in many regions. Our data can show that indigenous people have lived on these lands for hundreds or thousands of years before Europeans came to the continent, and these types of data can be used in currently policy decisions regarding the land rights and ownership of indigenous people in certain areas.
3. What are the overall objectives?
The overall objectives of the ALPHA project are to generate data on the types, timing, duration, and locations of past human activities in Amazonian forests, and how/whether these activities leave signals that are still present in modern forests. We also aim to link these findings with current ecological and biogeographical patterns and processes documented in Amazonian forests over the last several decades. We aim to integrate past and modern ecology because what we observe and monitor today is usually dependent on processes that have occurred in the past, particularly in systems where individual trees live for hundreds of years - much longer than modern observations can see.
1. We have generated multiple publications on fire ages and fire histories for multiple plots across western Amazonia, including the long-term plots and many of the single-survey plant inventory plots in northwestern and southwestern Amazonia and in Suriname and Panama. A major finding out of these works is that while there some patterns of synchronicity within regions and even between regions, there is still a lot of heterogeneity involving past fires on local scales. The time since last fire ranges from modern in some forest plots to over 2000 years ago.
2. We have also generated multiple publications on the vegetation histories from the same forest plots using phytoliths, which are silica microfossils found in soils. Like fire, vegetation change has also been quite heterogeneous on within and between regions, yet some distinguishable patterns have emerged. A major pattern seen has been the consistency in increases in palm abundances during the last two thousand years. We have seen this pattern in parts of all surveyed regions (northwestern and southwestern Amazonia, Panama, and Suriname. The documented trends vary amongst species (i.e. species enrichments and depletions) and across geographic space. We are still exploring the drivers behind the variation these patterns.
3. We synthesized existing paleoecological and archaeological records Amazonia that resulted in impactful publications with state-of-art-ideas and findings: i) early human influences exerted gradual impacts on Amazonian systems, and that the abrupt and drastic changes like we were seeing in the soil records happened in the last 2000 years (Philosophical Transactions of the Royal Society), ii) widespread site abandonment occurred several centuries before European arrival (Science). We also produced temporally continuous reconstructions of fire and vegetation in northwestern and southwestern Amazonia to complement the data generated in the first two work packages and previous work on soil cores, and have several more that are still in progress.
4. We are working on the three-pronged approach (low, mid, and high risk) to assess how past human activities affect modern forest composition and carbon dynamics. We compared botanical inventory data from 1521 forest plots with modeled geographic distributions of people during the pre- and post-Columbian periods and found that: i) the geographic distribution of sites occupied during the pre-Columbian and colonial era (i.e. during the Jesuit and Rubber Boom periods) are significantly and positively correlated, ii) that modern vegetation patterns in many area may reflect legacies from the pre- and post-Columbian period, and iii) legacies can be positive (enrichment) or negative (depletion) in nature. Our next steps will be to compare the empirical paleoecological datasets with the model predictions and modern plant abundance data. We have also matched modern phytolith and pollen assemblages from the soil and lake surface samples with observed modern vegetation characteristics, and used these relationships to quantify past environmental parameters. In a recent special issue on anthromes and carbon dynamics in New Phytologist, we showed that forest cover percentages at Lake Kumpak in the Ecuadorian Amazonia had forest cover percentages around the lake ranging from from 48–84% and biomass ranges 142–438 Mg ha−1 over the last 2000 years.
2. We have also generated multiple publications on the vegetation histories from the same forest plots using phytoliths, which are silica microfossils found in soils. Like fire, vegetation change has also been quite heterogeneous on within and between regions, yet some distinguishable patterns have emerged. A major pattern seen has been the consistency in increases in palm abundances during the last two thousand years. We have seen this pattern in parts of all surveyed regions (northwestern and southwestern Amazonia, Panama, and Suriname. The documented trends vary amongst species (i.e. species enrichments and depletions) and across geographic space. We are still exploring the drivers behind the variation these patterns.
3. We synthesized existing paleoecological and archaeological records Amazonia that resulted in impactful publications with state-of-art-ideas and findings: i) early human influences exerted gradual impacts on Amazonian systems, and that the abrupt and drastic changes like we were seeing in the soil records happened in the last 2000 years (Philosophical Transactions of the Royal Society), ii) widespread site abandonment occurred several centuries before European arrival (Science). We also produced temporally continuous reconstructions of fire and vegetation in northwestern and southwestern Amazonia to complement the data generated in the first two work packages and previous work on soil cores, and have several more that are still in progress.
4. We are working on the three-pronged approach (low, mid, and high risk) to assess how past human activities affect modern forest composition and carbon dynamics. We compared botanical inventory data from 1521 forest plots with modeled geographic distributions of people during the pre- and post-Columbian periods and found that: i) the geographic distribution of sites occupied during the pre-Columbian and colonial era (i.e. during the Jesuit and Rubber Boom periods) are significantly and positively correlated, ii) that modern vegetation patterns in many area may reflect legacies from the pre- and post-Columbian period, and iii) legacies can be positive (enrichment) or negative (depletion) in nature. Our next steps will be to compare the empirical paleoecological datasets with the model predictions and modern plant abundance data. We have also matched modern phytolith and pollen assemblages from the soil and lake surface samples with observed modern vegetation characteristics, and used these relationships to quantify past environmental parameters. In a recent special issue on anthromes and carbon dynamics in New Phytologist, we showed that forest cover percentages at Lake Kumpak in the Ecuadorian Amazonia had forest cover percentages around the lake ranging from from 48–84% and biomass ranges 142–438 Mg ha−1 over the last 2000 years.
Besides the novel findings described above, we have also developed methodologies that are beyond the existing state-of-the-art of paleoecological analysies. We have developed methods to standardize charcoal records for cross site comparisons, developed and applied methodologies to infer fire intensity (burn temperature) from charcoal fragments using FTIR Spectroscopy, and developed and applied quantifications in past changes in forest cover and biomass using pollen and phytoliths. These methodologies are all significantly advancing the field of paleoecology and our understand about how past human activities have shaped Amazonian forests.
We expect to continuing publishing on the data and findings of this project in the upcoming years.
We expect to continuing publishing on the data and findings of this project in the upcoming years.