Human impacts on the environment and wildlife in California’s past: Lessons from California archaeology

The long history of human-animal interactions in California prior to European contact is frequently not considered when setting ecological baselines and, by consequence, when planning conservation and management expectations and strategies for native species. This article reviews archaeological perspectives that explore the relationship between human niche construction, plant and wildlife populations, and human health in pre-European contact Central California, with an emphasis on the Central Valley and Delta, the surrounding foothills, and the San Francisco Bay Area. A summary of the archaeological record for Central California is provided, along with how niche construction and related evolutionary based models have been used in prehistoric California. Examples of the influences of human niche construction on flora, fauna, and human health from the archaeological and ethnographic record are then discussed. This information is tied to modern wildlife research and management practices that would serve contemporary fish and wildlife management given that human influences on species “natural” habitats and ecological baselines extends much further into the past than current ecological baselines and wildlife management strategies traditionally recognize.

A multi-disciplinary perspective to nuance the narrative of tree planting as a nature-based solution

From global nature conservation policies to carbon off-set private initiatives, the focus on tree promotion, and tree planting in particular, as a nature-based solution to global environmental crises such as climatic change and biodiversity loss dominates the current discourse. Yet, this fixation on trees does not reflect a scientific consensus on the benefits of tree planting across diverse ecosystems and can have problematic implications from both an ecological and socio-political perspective. In this paper, we synthesise cross-disciplinary insights to challenge the common storyline of tree planting as a one-size-fits-all, nature-based solution to climate change and biodiversity loss. We discuss the appeal of tree planting as a panacea, and how this conflicts with reality, in which a diverse range of stakeholders represent various perspectives and pursue a plurality of goals. We assess the communicative aspects of trees and forests, exploring the symbolic power of a ‘tree’ and how practices in remote-sensing and scientific modelling reinforce the dominant tree planting narrative. We then reflect on the ecological and human contexts that need to be considered in planning of tree planting and how historical ecological baselines continue to influence ecosystem management goals. Finally, we explore how current conservation narratives value forest over other kinds of nature and demonstrate the important – but overlooked – role that non-forest landscapes such as open and semi-open vegetation play in climate change mitigation and biodiversity conservation. We conclude that we need to rethink the dominant tree-planting narrative, being mindful and critical of the socio-political drivers behind tree planting initiatives and potential biases, and allow ecological and sociocultural contexts to inform tree-promotion efforts and appropriateness.

Herbaria macroalgae as a proxy for historical upwelling trends in Central California

Planning for future ocean conditions requires historical data to establish more informed ecological baselines. To date, this process has been largely limited to instrument records and observations that begin around 1950. Here, we show how marine macroalgae specimens from herbaria repositories may document long-term ecosystem processes and extend historical information records into the nineteenth century. We tested the effect of drying and pressing six macroalgae species on amino acid, heavy metal and bulk stable isotope values over 1 year using modern and archived paper. We found historical paper composition did not consistently affect values. Certain species, however, had higher variability in particular metrics while others were more consistent. Multiple herbaria provided Gelidium (Rhodophyta) samples collected in southern Monterey Bay from 1878 to 2018. We examined environmental relationships and found δ 15 N correlated with the Bakun upwelling index, the productivity regime of this ecosystem, from 1946 to 2018. Then, we hindcasted the Bakun index using its derived relationship with Gelidium δ 15 N from 1878 to 1945. This hindcast provided new information, observing an upwelling decrease mid-century leading up to the well-known sardine fishery crash. Our case study suggests marine macroalgae from herbaria are an underused resource of the marine environment that precedes modern scientific data streams.

Leveraging legacy archaeological collections as proxies for climate and environmental research

Understanding the causes and consequences of previous climate changes is essential for testing present-day climate models and projections. Archaeological sites are paleoenvironmental archives containing unique ecological baselines with data on paleoclimate transformations at a human timescale. Anthropogenic and nonanthropogenic forces have destroyed many sites, and others are under immediate threat. In the face of this loss, previously excavated collections from these sites—referred to as legacy collections—offer a source of climate and other paleoenvironmental information that may no longer exist elsewhere. Here, we 1) review obstacles to systematically using data from legacy archaeological collections, such as inconsistent or unreported field methods, inadequate records, unsatisfactory curation, and insufficient public knowledge of relevant collections; 2) suggest best practices for integrating archaeological data into climate and environmental research; and 3) summarize several studies to demonstrate the benefits and challenges of using legacy collections as archives of local and regional environmental proxies. Data from archaeological legacy collections contribute regional ecological baselines as well as serve to correct shifting baselines. They also enable regional climate reconstructions at various timescales and corroborate or refine radiocarbon dates. Such uses of legacy collections raise ethical concerns regarding ownership of and responsibility for cultural resources and highlight the importance of Indigenous involvement in planning and executing fieldwork and stewardship of cultural heritage. Finally, we discuss methodologies, practices, and policies pertaining to archaeological legacy collections and support calls for discipline-wide shifts in collections management to ensure their long-term utility in multidisciplinary research and public engagement.

Estimating Downcore Decline in Skeletal Disintegration Risk in Holocene Environments

<p>Preservation of skeletal remains is thought to be positively linked to rate of burial, i.e., they are exposed to destructive processes for a shorter time under higher burial. However, downcore changes in time-averaging documented in Holocene skeletal assemblages implies that per-individual burial rates of skeletal remains of the same age cohort can be variable, e.g., owing to bioturbation, and estimation of time (and sediment depth) over which skeletal remains are exposed to destruction is not straightforward.</p><p>This variability in the depth of burial exposes them to different intensities of destructive processes that is typically highest in sediments on or close to the seafloor, and accordingly changes their probability of disintegration. This hinders both the reconstruction of taphonomic conditions downcore and the reconstruction of biological archives from age cohorts of skeletal remains.</p><p>We present the AALPS (Aging ALong burial PathS) model to estimate downcore disintegration risk and taphonomic age, based on sediment-depth distribution of postmortem age of individual skeletal remains. This model can be applied to individual cores and taxa, accounts for sediment mixing and time-averaging, and incorporates knowledge of changing sediment input.</p><p>As an application, we discriminate between distinct hypotheses of changes in skeletal disintegration rates in cores from the Adriatic Sea.</p><p>The method provides new insights into the taphonomy of skeletal remains in Holocene and Anthropocene environments and age unmixing of paleoecological time series, which can be used in conservation paleobiology to reconstruct ecological baselines to guide future conservation efforts.</p>

Unshifting the baseline: a framework for documenting historical population changes and assessing long-term anthropogenic impacts

Ecological baselines—reference states of species' distributions and abundances—are key to the scientific arguments underpinning many conservation and management interventions, as well as to the public support to such interventions. Yet societal as well as scientific perceptions of these baselines are often based on ecosystems that have been deeply transformed by human actions. Despite increased awareness about the pervasiveness and implications of this shifting baseline syndrome, ongoing global assessments of the state of biodiversity do not take into account the long-term, cumulative, anthropogenic impacts on biodiversity. Here, we propose a new framework for documenting such impacts, by classifying populations according to the extent to which they deviate from a baseline in the absence of human actions. We apply this framework to the bowhead whale ( Balaena mysticetus ) to illustrate how it can be used to assess populations with different geographies and timelines of known or suspected impacts. Through other examples, we discuss how the framework can be applied to populations for which there is a wide diversity of existing knowledge, by making the best use of the available ecological, historical and archaeological data. Combined across multiple populations, this framework provides a standard for assessing cumulative anthropogenic impacts on biodiversity. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

Historical Degradation and Ecological Recovery

Spanish arrival to Alta and Baja California in AD 1542 marked the beginning of widespread ecological changes for California Island ecosystems. Over several centuries, Native peoples were removed to mainland towns and missions, intensive commercial fisheries and ranching operations developed, and numerous exotic plants and animals were introduced. The ecological fallout was swift and extensive, with extinctions and extirpations, devegetation, severe soil erosion, damaged hydrology, collapsed fisheries, and other ecological impacts. Archaeologists have long recognized some of the effects of these historical impacts, but only after decades of restoration biology on the islands have we come to appreciate how dramatically ecological baselines have shifted since Spanish arrival. As a result, many of California's islands now appear to have been optimal rather than marginal for human occupation.