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The Climate Research & Development Program (Climate R&D) in the Ecosystems Mission Area (EMA) covers a tremendous breadth of topics important to understanding how climate, land-use, and environmental change are affecting ecosystems.

One of the qualities that sets the Climate R&D program apart from other programs in USGS is the fact that it funds a substantial amount of paleoclimate/paleoecology research. USGS scientists are at the cutting edge of developing new paleo methods for expanding our understanding of past climate, which can help inform mechanisms underpinning past and potential future ecosystem and resource change leading to improved models of future climate. Here we feature three examples of innovative paleo approaches developed by USGS scientists and their colleagues: (1) dating ice cores from ice patches; (2) measuring yearly growth layers in clamshells; and (3) combining paleo data with Indigenous Tribal Ecological Knowledge (ITEK). 

Prepping the Drilling Location in an Ice Patch
Field assistants prepare the trail and drilling location on mountain ice patch.

Dr. Greg Pederson is developing methods for coring and dating ice patches so that thousands of years of incremental ice accumulation can be used to reconstruct past cool-season climate. Previously, only large glaciers and ice sheets have been cored, but those are limited to polar regions or produce short records (in the case of glaciers) due to ice transport. Ice patches, on the other hand, have a near global distribution in high mountain areas and can produce long records to develop a better understanding of Holocene climate variability. As in other ice cores, oxygen isotopes from the ice help to explain past climate conditions. Using a novel approach, scientists are developing accurate age-depth models by radiocarbon dating organic material in the ice cores despite being unable to count annual layers in the ice - the more traditional method used on polar ice cores. Since ice patches are widely distributed around the world, this new method and proxy data source may make it possible to better understand millennial-scale changes in climate over the Holocene for critical high-elevation ecosystems and water resource generating regions.

Researchers retrieving ice cores from an ice patch
Researchers retrieving ice cores from an ice patch located on the Beartooth Plateau, Wyoming.

In the marine environment, the opposite geographic constraint has been true. In paleo studies, tropical corals are one of the most valuable archives for reconstructing annually-resolved marine climate. At higher latitudes outside the tropics, marine paleoclimate is more often inferred from more readily accessible terrestrial-based archives, like tree-rings and ice cores, or decadally-resolved archives like ocean sediments. To address this, Dr. Madelyn Mette (2021) is applying novel methods using shells from ocean quahogs (clams) to reconstruct annual marine paleoclimate at high latitudes. Some clams are very long-lived (hundreds of years), and each year the clams create a new growth layer in their shells, analogous to tree rings. The chemical composition of the shell layers, particularly the oxygen isotope ratio, can be used to reconstruct historic sea surface temperatures. Because of the unique bar-code-like growth pattern of the annual layers, dead-collected shells can be precisely dated by overlapping (matching) the pattern with live-collected shells, enabling the construction of very long shell-growth chronologies that go back hundreds or even thousands of years.

diagram of bivalve proxy archive
Clamshell proxy archive. A) Arctica islandica shell and B) photomicrograph of a shell cross-section showing annual growth increments.

These first two innovative paleo methods are expanding where on the planet we can gather paleo data to understand past climate, but we can also combine paleo data with other ways of knowing to improve our understanding of past climate. For example, Dr. Clarke Knight and her colleagues combined Indigenous Tribal Ecological Knowledge (ITEK) based on the oral histories of the Karuk and Yurok Tribes with paleo data from pollen, tree fire scars, and sedimentary charcoal in order to better understand fire history and forest conditions over the last millennium in northwestern California. Under the Karuk Tribe’s Practicing Pikyav policy, the paleo scientists and tribal communities developed a research proposal that specified the scientists’ research interests and how the collaboration would honor tribal intellectual property, data sharing, and reciprocity requests. The proposal underwent tribal review and approval. During the writing process, the Tribe was able to contribute valuable knowledge at their comfort level and provide comments on any aspect of the document. After publication, the scientists participated in workshops to share findings with the Tribe and community members and Tribal communication liaisons were included in media requests to ensure their participation in broader messaging of the research. This process demonstrated that engagement with Tribal partners is a key part of paleoecological research that implicates Indigenous people.

Douglas-fir forest in northwestern California
Dense stands of Douglas-fir surround South Twin Lake in the Klamath bioregion of northwestern California.

Weaving ITEK with analysis of paleo data can strengthen data interpretations and ultimately improve conservation policy and land management. Of note, the study demonstrated the strong influence of Indigenous stewardship on forest conditions in northern California for at least a millennium. Indigenous burning practices coupled with lightning-induced fires kept forest carbon low, at approximately half of what it is today, and kept forests more open and less dense, which enhanced the resiliency and health of the fire-prone forests of northern California. However, colonization and twentieth century fire suppression policies have densified California forests, making them more prone to catastrophic large wildfire than in the past.  

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