Climate change poses escalating risks to urban populations and infrastructure, making adaptation strategies urgent. We overlaid the pre-urban, natural hydrology of New York City's five boroughs with places that flood today and predictions of future flooding to identify coincident localities ("Blue Zones") where adaptation is needed. We identified 538 Blue Zones, which collectively cover 21% of the city's land area, affecting approximately 1.2 million people and 11% of city buildings. Over two-thirds of the flood-prone area is estimated to be threatened by coastal flooding; 36% from combined coastal and pluvial flooding; and 5% from pluvial flooding only. Analysis of land tenure revealed that two-thirds of Blue Zone area is managed by government entities. Urban historical ecology provides important insights not only about the past but the future of cities.

ABSTRACT Aim Indigenous range maps are fundamental documents in biogeography, phylogeny and conservation. We define the indigenous range of a species as ecoregions (or parts of ecoregions) where the species was likely found before humans became a major factor shaping the species' distribution, beginning at a time when the geographical alignment of the continents and the prevailing climate are (or at least were) roughly consistent with current conditions. We developed a structured, generally applicable method to map a species' indigenous range and applied this process to the tiger ( Panthera tigris ). Location Terrestrial Asia. Methods To guide our mapping, we synthesised a database of over 70,000 tiger observations with dates and locations. We developed a structured Delphi process to assign categories of indigenous range to ecoregions aided by a climate niche model. We analysed tiger habitat change at the ecoregional scale using the anthropogenically modified biomes (‘Anthrome 12K’) dataset to suggest dates of first significant human impact. Finally, we estimated extirpation dates for ecoregions where tigers have been extirpated. Results We found the tiger once occupied a likely indigenous resident range of approximately 11.5 million km 2 , crossing 116 ecoregions. We also mapped an additional c. 11.7 million km 2 of exploratory range and 1.2 million km 2 of possible resident range. Collectively these areas overlap with 36 modern countries. Significant human disruption of the species' habitat seems to have begun over 6000 years ago in some areas, but in other regions has yet to materialise. In few arid ecoregions, human activities appear to have modestly increased habitat availability in the past, yet overall tigers have lost between 90% and 95% of their indigenous range over the last 8500 years. Main Conclusions We define the ‘indigenous range’ of a species, develop a replicable biogeographical procedure, apply the procedure to the tiger and discuss transferability to other species.

Of all the ways human beings have modified the planet over the last 10,000 years, habitat loss is the most important for other species. To address this most critical threat to biodiversity, governments, non-governmental actors, and the public need to know, in near real-time, where and when habitat loss is occurring. Here we present an integrated habitat modelling system at the range-wide scale for the tiger (Panthera tigris) to measure and monitor changes in tiger habitat at range-wide, national, biome, and landscape scales, as often as the underlying inputs change. We find that after nearly 150 years of decline, effective potential habitat for the tiger seems to have stabilized at around 16% of its indigenous extent (1.817 million km2). As of the 1st of January 2020, there were 63 Tiger Conservation Landscapes in the world, covering 911,920 km2 shared across ten of the 30 modern countries which once harbored tiger populations. Over the last 20 years, the total area of Tiger Conservation Landscapes (TCLs) declined from 1.025 million km2 in 2001, a range-wide loss of 11%, with the greatest losses in Southeast Asia and southern China. Meanwhile, we documented expansions of modelled TCL area in India, Nepal, Bhutan, northern China, and southeastern Russia. We find significant potential for restoring tigers to existing habitats, identified here in 226 Restoration Landscapes. If these habitats had sufficient prey and were tigers able to find them, the occupied land base for tigers might increase by 50%. Our analytical system, incorporating Earth observations, in situ biological data, and a conservation-oriented modelling framework, provides the information the countries need to protect tigers and enhance habitat, including dynamic, spatially explicit maps and results, updated as often as the underlying data change. Our work builds on nearly 30 years of tiger conservation research and provides an accessible way for countries to measure progress and report outcomes. This work serves as a model for objective, range-wide, habitat monitoring as countries work to achieve the goals laid out in the Sustainable Development Goals, the 30×30 Agenda, and the Kunming-Montreal Global Biodiversity Framework.

Green roofs provide multiple benefits including reducing the urban heat island effect, absorbing stormwater and air pollution, and serving as habitat for wildlife. However, many cities have not taken advantage of green roofs as a nature-based solution. In New York City (NYC), approximately 20% of the landscape is covered by buildings, thus rooftops present a substantial opportunity for expanding green infrastructure. Spatial data on green roofs are critical for understanding their abundance and distribution, what filters may drive spatial patterns, and who benefits from them. We describe the development of a green roof dataset for NYC based on publicly available data and classification of aerial imagery from 2016. Of the over one million buildings in NYC, we found only 736 with green roofs (<0.1%), although there may have been others we did not detect. These green roofs are not evenly distributed in NYC - they are most common in midtown and downtown Manhattan, while most other areas have few to none. Green roofs tend to be more prevalent in parts of NYC with combined sewer systems, but some such areas, and those with the most heat-vulnerable communities, have few if any despite their potential to help ameliorate stormwater and urban heat challenges. Though green roofs are providing some benefits within NYC, we anticipate they are filtered based on dynamics of infrastructure, institutions, and perceptions, rather than targeted to address climate and weather-related challenges. There is substantial opportunity in NYC to increase green roofs, and equity of them. The dataset we developed is publicly available and can serve as a baseline for tracking these assets through time, while supporting further research, conversations, and policies related to the benefits and distribution of green roofs. The underlying methods can also be applied to help fill similar data gaps in other cities.

The purpose of this white paper is to support an initial set of recommended individual actions for Wild for All, an effort to encourage more people to experience the wonders of nature, and to take steps to protect the world’s wildlife and wild spaces – not only in faraway places, but also the everyday wild at our doorsteps too. Wild For All is a collaborative initiative with the Wildlife Conservation Society (WCS), Freeborne Impact, and Higher Ground. The campaign was launched in conjunction with the Netflix series Our Great National Parks, a five-part series narrated by President Barack Obama. Wild For All is powered by Count Us In.

AbstractIn April 2019, the U.S. Fish and Wildlife Service (USFWS) released its recovery plan for the jaguar Panthera onca after several decades of discussion, litigation and controversy about the status of the species in the USA. The USFWS estimated that potential habitat, south of the Interstate-10 highway in Arizona and New Mexico, had a carrying capacity of c. six jaguars, and so focused its recovery programme on areas south of the USA–Mexico border. Here we present a systematic review of the modelling and assessment efforts over the last 25 years, with a focus on areas north of Interstate-10 in Arizona and New Mexico, outside the recovery unit considered by the USFWS. Despite differences in data inputs, methods, and analytical extent, the nine previous studies found support for potential suitable jaguar habitat in the central mountain ranges of Arizona and New Mexico. Applying slightly modified versions of the USFWS model and recalculating an Arizona-focused model over both states provided additional confirmation. Extending the area of consideration also substantially raised the carrying capacity of habitats in Arizona and New Mexico, from six to 90 or 151 adult jaguars, using the modified USFWS models. This review demonstrates the crucial ways in which choosing the extent of analysis influences the conclusions of a conservation plan. More importantly, it opens a new opportunity for jaguar conservation in North America that could help address threats from habitat losses, climate change and border infrastructure.

Reintroduction—defined here as the return of a species to a part of its range where it has been extirpated—is a critical pathway to conservation in the 21st century. As late as the 1960s, jaguars ( Panthera onca ) inhabited an expansive region in the central mountain ranges of Arizona and New Mexico in the United States, a habitat unique in all of jaguar range. Here, we make the case for reintroduction, building a rhetorical bridge between conservation science and practice. First, we present a rationale rooted in the philosophy of wildlife conservation. Second, we show that the species once occupied this territory and was extirpated by human actions that should no longer pose a threat. Third, we demonstrate that the proposed recovery area provides suitable ecological conditions. Fourth, we discuss how return of the species could be a net benefit to people, explicitly recognizing a diversity of values and concerns. Fifth, we show that reintroduction is practical and feasible over a realistic time horizon. Returning the jaguar to this area will enhance the recovery of an endangered species in the United States, further its range‐wide conservation, and restore an essential part of North America's cultural and natural heritage.

In recent centuries, human activities have greatly modified the geomorphology of coastal regions. However, studies of historical and possible future changes in coastal flood extremes typically ignore the influence of geomorphic change. Here, we quantify the influence of 20th-century manmade changes to Jamaica Bay, New York City, on presentday storm tides. We develop and validate a hydrodynamic model for the 1870s based on detailed maps of bathymetry, seabed characteristics, topography, and tide observations for use alongside a present-day model. Predominantly through dredging, landfill, and inlet stabilization, the average water depth of the bay increased from 1.7 to 4.5 m, tidal surface area decreased from 92 to 72 km(2), and the inlet minimum cross-sectional area expanded from 4800 to 8900 m(2). Total (freshwater plus salt) marsh habitat area has declined from 61 to 15 km(2) and intertidal unvegetated habitat area from 17 to 4.6 km(2). A probabilistic flood hazard assessment with simulations of 144 storm events reveals that the landscape changes caused an increase of 0.28 m (12 %) in the 100-year storm tide, even larger than the influence of global sea level rise of about 0.23 m since the 1870s. Specific anthropogenic changes to estuary depth and area as well as inlet depth and width are shown through targeted modeling and dynamics-based considerations to be the most important drivers of increasing storm tides.

Species interactions matter to conservation. Setting an ambitious recovery target for a species requires considering the size, density, and demographic structure of its populations such that they fulfill the interactions, roles, and functions of the species in the ecosystems in which they are embedded. A recently proposed framework for an International Union for Conservation of Nature Green List of Species formalizes this requirement by defining a fully recovered species in terms of representation, viability, and functionality. Defining and quantifying ecological function from the viewpoint of species recovery is challenging in concept and application, but also an opportunity to insert ecological theory into conservation practice. We propose 2 complementary approaches to assessing a species' ecological functions: confirmation (listing interactions of the species, identifying ecological processes and other species involved in these interactions, and quantifying the extent to which the species contributes to the identified ecological process) and elimination (inferring functionality by ruling out symptoms of reduced functionality, analogous to the red-list approach that focuses on symptoms of reduced viability). Despite the challenges, incorporation of functionality into species recovery planning is possible in most cases and it is essential to a conservation vision that goes beyond preventing extinctions and aims to restore a species to levels beyond what is required for its viability. This vision focuses on conservation and recovery at the species level and sees species as embedded in ecosystems, influencing and being influenced by the processes in those ecosystems. Thus, it connects and integrates conservation at the species and ecosystem levels.

Species-area relationship models are useful in conservation planning; however these models could be strengthened with the addition of a latitudinal factor. We built latitude-enhanced species-area relationship models to predict species richness for a variety of common taxa in the eastern United States at local to regional scales. We used data from complete surveys of East Coast parks in the United States to build latitude-enhanced species-area relationship models for amphibians, birds, freshwater fish, mammals, marine fish, plants, and reptiles. We used data from the published literature and United States Fish and Wildlife Refuges to independently test the accuracy of the models. We demonstrated the utility of all modeled taxa within selected East Coast Protected Areas of the United States. Our models explained 35–91% of the variation in surveyed species richness, with marine fish, freshwater fish and reptile models exhibiting the strongest relationships (pseudo-R2 = 0.91, 0.66, and 0.70, respectively). Latitude had the strongest influence in the amphibian model. During accuracy testing, all taxa exhibited significant agreement between observed and predicted species richness and explained 75–97% of the variation. Our demonstration showed that for two similarly sized US Protected Areas, the parcel l.25° lower in latitude would likely have one more bird species, four more plant species, and an additional amphibian species. The latitude term added value to the species-area relationship models for most taxa and proved useful for conservation and urban planning in local to regional sized areas of the East Coast of the United States.

Over the last century, numbers of wild tigers (Panthera tigris) have crashed, while human populations have boomed. Here we investigate future trajectories of human population within tiger range through analysis of the shared socio-economic pathways (SSPs). These five pathways describe urban, rural and total population distributions by decade through 2100, based on plausible but contrasting scenarios of economic, education, migration, and urbanization policy. In 2010 approximately 57 million people lived in regions defined as "tiger conservation landscapes" (or TCLs); 8% of sympatric people lived in towns and cities that occupied 4% of tiger range. We show that tigers could share these same geographies with as few as 40 million (30% decline compared to 2010) or as many as 106 million people (an increase of 85%) by 2100. Those populations could be as much as 64%, or as little as 17%, urbanized, depending on the pathway. Urban areas are likely to expand, displacing between 6 and 22% of tiger's current range, depending on how urban growth is managed. Human population density thresholds compatible with tigers vary by region, from 140 persons/km(2) in the Indian subcontinent, to 10 persons/km(2) in the Russian Far East and northern China. SSP3, a future where nations indulge regional rivalries, would make conservation more difficult, whereas SSP1, with a focus on well-managed urbanization and education, could help relieve pressures. Tigers are a conservation-reliant species and will likely remain so through the 21st century, therefore we suggest coupling continued site-level protection with efforts to develop constituencies for conservation in Asia's burgeoning cities.

Efforts to designate priority areas for conservation have had a long history, with most modern initiatives focused on either designating areas important for biodiversity or those least impacted by direct human disturbance. Ecologically intact ecosystems are becoming increasingly limited on the planet, making their identification and conservation an important priority. Intact forest landscapes (IFL) are defined as forests that are mainly free of significant anthropogenic degradation and at least 500 km(2) in size. Here we define a new metric, the Last of the Wild in each Ecoregion (LWE), as a preliminary scoping of the most intact parts of each ecoregion. IFL and LWE are approaches among a broad family of techniques to mapping ecological integrity at the global scale. Although both implicitly include species integrity as a dimension of intactness, this is inferred rather than directly measured. We assessed whether IFL or LWE areas were better at capturing species where they are most abundant using species distribution data for a set of forest species for which range-wide data were available and human activity limits the range. We found that IFL and LWE methods identified areas where species we assessed are either absent or at too low an abundance to be ecologically functional. As such many IFL/LWE polygons did not have intact fauna. We also show that 54.7% of the terrestrial realm (excluding Antarctica) has at least one species recorded as extinct and that two thirds of IFL/LWE areas overlap with areas where species have gone extinct in the past 500 years. The results show that even within the most remote areas, serious faunal loss has taken place at many localities so direct species survey work is also needed to confirm faunal intactness.

Conservation BiologyVolume 33, Issue 5 p. 1208-1210 Comment A full and authentic reckoning of species’ ranges for conservation: response to Akçakaya et al. 2018 Eric W. Sanderson, Eric W. Sanderson esanderson@wcs.org orcid.org/0000-0002-7477-0193 Wildlife Conservation Society – Global Conservation Programs, 2300 Southern Blvd., Bronx, NY, 10460 U.S.A.Search for more papers by this author Eric W. Sanderson, Eric W. Sanderson esanderson@wcs.org orcid.org/0000-0002-7477-0193 Wildlife Conservation Society – Global Conservation Programs, 2300 Southern Blvd., Bronx, NY, 10460 U.S.A.Search for more papers by this author First published: 16 August 2019 https://doi.org/10.1111/cobi.13399Citations: 15 Article impact statement: : Defining the full recovery of species requires historical baselines from times prior to range loss imposed by human activity. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume33, Issue5October 2019Pages 1208-1210 RelatedInformation

Resilience to extreme weather events and other sudden changes is an issue facing many communities in the early twenty-first century. Planning to respond to disasters is particularly complicated in densely inhabited, multi-jurisdictional urban social-ecological systems like the watershed of Jamaica Bay, a large urbanized estuary on the south side of New York City. This area contains parklands managed by New York City, the National Park Service, and other agencies, four sewage treatment plants, three former landfills, and urban and suburban communities, all of which were heavily impacted by Hurricane Sandy in 2012. Here successful resilience planning and response requires participation from a wide variety of government and civil society players each with different types of knowledge, value systems, and expectations about what resilience means. To investigate how visions of future resilience differed among several communities living in or concerned with Jamaica Bay, New York, we deployed a free, Internet-based modeling framework called Visionmaker that enabled interactive scenario creation and testing. Through a series of standardized workshops, we recruited participants from a variety of different communities of practice (i.e. researchers, land managers, educators, non-governmental organization staff, and community board members) to design visions of resilience. Visions spanned terrestrial and marine environments and contained natural and built ecosystems. Most users favored increasing resilience through expanding salt marsh and green infrastructure while, for the most part, keeping the built city landscape of streets and buildings intact. We compare and contrast these visions and discuss the implications for future resilience planning in coastal cities.

This project implemented a participatory process with key stakeholders to evaluate current and potential future resilience-related investments in Jamaica Bay. The process was designed to consider baywide concepts that could reduce future flood risk exposure while also improving water quality, restoring habitat in and around the bay, and more generally improving resilience to extreme weather events.

For the first time in the Anthropocene, the global demographic and economic trends that have resulted in unprecedented destruction of the environment are now creating the necessary conditions for a possible renaissance of nature. Drawing reasonable inferences from current patterns, we can predict that 100 years from now, the Earth could be inhabited by between 6 and 8 billion people, with very few remaining in extreme poverty, most living in towns and cities, and nearly all participating in a technologically driven, interconnected market economy. Building on the scholarship of others in demography, economics, sociology, and conservation biology, here, we articulate a theory of social-environmental change that describes the simultaneous and interacting effects of urban lifestyles on fertility, poverty alleviation, and ideation. By recognizing the shifting dynamics of these macrodrivers, conservation practice has the potential to transform itself from a discipline managing declines ("bottleneck") to a transformative movement of recovery ("breakthrough").

It is well-known that rising sea levels will increase pressure along shorelines, yet how society and natural systems will respond is uncertain. Natural systems such as wetlands can respond dynamically to changing conditions, and recent sea level rise has been matched in many places with a rising marsh substrate. The societal response to increasing flooding by necessity is adaptation, particularly in areas with a higher population. However, the subsequent influences on flooding, habitat, and water quality have rarely been evaluated. Jamaica Bay, NY is a coastal embayment bounded on the south by the Rockaway Peninsula and the Atlantic Ocean, on the north by Brooklyn, Queens, and Nassau counties, on the east by the John F. Kennedy Airport, and to the lower bay of New York Harbor on the west through the Rockaway Inlet (Sanderson et al. 2016). The Bay perimeter is home to a large human population, as well as a variety of wildlife that live within the Bay’s salt marsh and adjacent upland ecosystems. The Bay has been identified as an area where ecosystem restoration will potentially have a major impact for protection of the Bay’s population, as well as enhancing the recreational, commercial, and ecological services the Bay provides.

American Journal of BotanyVolume 104, Issue 5 p. 645-648 On the Nature of ThingFree Access Toward principles of historical ecology Erin Beller, Corresponding Author Erin Beller [email protected] Resilient Landscapes Program, San Francisco Estuary Institute, 4911 Central Avenue, Richmond, California 94804 USA Department of Geography, University of California Berkeley, 565 McCone Hall, Berkeley, California 94720 USAAuthor for correspondence (e-mail: [email protected])Search for more papers by this authorLoren McClenachan, Loren McClenachan Environmental Studies, Colby College, 5351 Mayflower Hill, Waterville, Maine 04901 USASearch for more papers by this authorAndrew Trant, Andrew Trant School of Environment, Resources and Sustainability, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3GSearch for more papers by this authorEric W. Sanderson, Eric W. Sanderson Wildlife Conservation Society Global Conservation Programs, 2300 Southern Blvd, Bronx, New York 10460 USASearch for more papers by this authorJeanine Rhemtulla, Jeanine Rhemtulla Forest and Conservation Sciences, University of British Columbia, 3609-2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4Search for more papers by this authorAnita Guerrini, Anita Guerrini School of History, Philosophy, and Religion, Oregon State University, 322 Milam Hall, Corvallis, Oregon 97331 USASearch for more papers by this authorRobin Grossinger, Robin Grossinger Resilient Landscapes Program, San Francisco Estuary Institute, 4911 Central Avenue, Richmond, California 94804 USASearch for more papers by this authorEric Higgs, Eric Higgs School of Environmental Studies, University of Victoria, Room 205, House 4, Victoria, British Columbia, Canada V8P 5C2Search for more papers by this author Erin Beller, Corresponding Author Erin Beller [email protected] Resilient Landscapes Program, San Francisco Estuary Institute, 4911 Central Avenue, Richmond, California 94804 USA Department of Geography, University of California Berkeley, 565 McCone Hall, Berkeley, California 94720 USAAuthor for correspondence (e-mail: [email protected])Search for more papers by this authorLoren McClenachan, Loren McClenachan Environmental Studies, Colby College, 5351 Mayflower Hill, Waterville, Maine 04901 USASearch for more papers by this authorAndrew Trant, Andrew Trant School of Environment, Resources and Sustainability, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3GSearch for more papers by this authorEric W. Sanderson, Eric W. Sanderson Wildlife Conservation Society Global Conservation Programs, 2300 Southern Blvd, Bronx, New York 10460 USASearch for more papers by this authorJeanine Rhemtulla, Jeanine Rhemtulla Forest and Conservation Sciences, University of British Columbia, 3609-2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4Search for more papers by this authorAnita Guerrini, Anita Guerrini School of History, Philosophy, and Religion, Oregon State University, 322 Milam Hall, Corvallis, Oregon 97331 USASearch for more papers by this authorRobin Grossinger, Robin Grossinger Resilient Landscapes Program, San Francisco Estuary Institute, 4911 Central Avenue, Richmond, California 94804 USASearch for more papers by this authorEric Higgs, Eric Higgs School of Environmental Studies, University of Victoria, Room 205, House 4, Victoria, British Columbia, Canada V8P 5C2Search for more papers by this author First published: 17 May 2017 https://doi.org/10.3732/ajb.1700070Citations: 24 Freely available online through the AJB open access option. AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Rising temperatures and sea levels, biological homogenization and biodiversity loss, habitat fragmentation, and other environmental changes are dramatically reshaping landscapes across the globe. In this context, understanding the patterns, drivers, and consequences of these changes has become one of the central challenges facing environmental scientists and managers today. Yet to do so requires a long-term perspective on environmental systems that predates many of the accelerated anthropogenic impacts of the recent past. How, then, can we understand these changes in the context of decade- and century-scale ecosystem trajectories and human history? What was the structure, function, and dynamics of ecosystems like before these changes? And how have people shaped these systems over time? These questions are the domain of historical ecology. Historical ecology is the study of nature over time, often (though not necessarily) with a focus on human–environment interactions and the causes and consequences of changes caused by human actions in the recent past (Crumley, 2003; Rhemtulla and Mladenoff, 2007). The field includes both researchers who wish to document ecological patterns and dynamics in the recent past using historical methods, as well as those interested in historicizing ecology—that is, understanding the relationships between nature and human culture over time (cf. Szabo [2014] for a detailed treatment). It draws on a broad range of qualitative and quantitative sources that vary in temporal and spatial coverage, require creative and thoughtful methods to synthesize and interpret, and are often integrated in ways that cross traditional disciplinary boundaries (Fig. 1). Data include traditional archival sources such as written documents, maps, oral histories, land surveys, landscape views and photography, along with biological and physical data such as sediment and pollen records, tree rings, species lists, and habitat relationships (Swetnam et al., 1999; Egan and Howell, 2001; Vellend et al., 2013). While relying on data from the past, historical ecology is an inherently future-oriented discipline given its emphasis on temporal dynamics and change trajectories (Higgs et al., 2014). It provides vivid narratives of past landscapes and change that are of interest to specialists and nonspecialists alike (e.g., Sanderson, 2009; Grossinger, 2012). Figure 1Open in figure viewerPowerPoint Historical ecology draws on a broad range of archival and biophysical sources that provide windows into the nature of past ecosystems and landscapes. A wide array of material is available for recent decades; artifacts, traditional ecological knowledge, and natural archives such as pollen cores shed light on earlier eras. ya = years ago. Historical ecology is part of a long tradition of understanding relationships between humans and environmental change and shares strong topical and methodological affinities with paleoecology, environmental history, and historical geography. It is similar to "temporal ecology" (sensu Wolkovich et al., 2014), though temporal ecology relies more on time series data, rather than integrating a broad array of data types within their historical context. Historical ecology has much in common with landscape and restoration ecology, ecological subfields that emphasize spatial patterns and processes, human–environment interactions, and temporal dynamism. As a field, historical ecology largely operates at the intersection of ecology, history, anthropology, and geography, using tools and techniques from all four disciplines to help people conceive of what populations, communities, ecosystems, and landscapes existed in the past and how they have changed over time (Szabó, 2014). It also relies heavily on the history of science, since interpretation of often fragmentary, qualitative, and idiosyncratic historical data requires an understanding of the historical, scientific, and cultural contexts in which past records and scientific data were produced (Raby, 2015). Studies cast a broad net of topics of interest, from traditional ecological questions such as documenting population abundance and community composition, habitat distribution, and ecological processes and functions, to geographic questions such as changes in geophysical patterns and processes (e.g., groundwater dynamics, stream morphology) and socioecological questions such as understanding traditional landscape management and setting goals and objectives for ecological restoration. As a result, historical ecology research is highly interdisciplinary and not restricted to a subfield of ecological science; rather, practitioners are spread across the humanities, social sciences, and natural sciences. While this interdisciplinarity is a source of strength, it has also complicated the consolidation of historical ecology into a unified field. Historical ecology has developed rapidly over the past two decades, especially with the adoption of geographic information systems, widespread digitization of historical documents and maps, and increased concern about the state of future landscapes. Yet unlike other related fields, historical ecology has no degree programs, no conference for its practitioners, and no journals dedicated to its study and advancement. Efforts to bring together scholars of historical ecology have largely occurred to date through topical conferences (e.g., Oceans Past) and at special sessions at conferences for other fields (e.g., at the American Association of Geographers, the American Society for Environmental History, International Association for Landscape Ecology, or the Ecological Society of America); similarly, historical ecological research is currently published in a broad variety of ecological, geographic, historical, and anthropological journals. While this certainly reflects the applicability of historical ecology to a wide range of disciplines, it may also limit potential advancements in the field that could be facilitated by dedicated venues. More importantly, perhaps, to date there has been no attempt at defining principles or a theory of historical ecology, despite the rapidly growing quantity of research in the field. We contend that the time is right to develop a unified framework for understanding temporal change in complex social–environmental systems. Here we provide background on the value of historical ecology and outline initial principles of historical ecology, with a view toward consolidating existing approaches. What does historical ecology contribute to the study of ecology? Historical ecology can provide novel insights across a uniquely broad range of ecological scales, from population to landscape. At the population level, historical ecology can address questions about long-term changes to population size, density, distribution, and structure. For example, 19th century fishing logs from the Scotian Shelf suggested biomass of Atlantic cod (Gadus morhua) was two orders of magnitude greater than fisheries scientists observed it to be in the 20th century, which changed views of the potential productivity of this system (Rosenberg et al., 2005). At the community level, historical ecology can address questions of how past changes in species dominance have contributed to observed changes in community stability. For example, in Caribbean coral reefs, a phase shift to algal-dominated systems was observed in the 1980s, with the proximate cause diagnosed as a disease in the most abundant herbivore, the spiny sea urchin (Diadema antillarum). However, historical analyses revealed that overfishing over centuries reduced the abundance of other herbivores, facilitating the rapid transition (McClenachan et al., 2015). At the ecosystem level, historical ecology can provide insight into long-term changes in resource-use patterns that can affect nutrient availability and ecosystem processes. For example, indigenous peoples of the Pacific Northwest have been harvesting shellfish for millennia, resulting in the movement of significant amounts of marine-derived nutrients into the nearby terrestrial ecosystem and creating legacies of enhanced forest productivity that persist today (Trant et al., 2016). At the landscape level, historical ecology can assess change and persistence in habitat type extent and distribution over time and link observed patterns to geophysical characteristics. For example, an analysis of land cover change along a large California river documented a formerly heterogeneous mosaic of riparian vegetation communities (including willow–cottonwood forested wetlands and xeric scrublands) linked to local variations in dry-season surface flow, then this analysis was used to identify priority locations with suitable conditions for riparian restoration (Beller et al., 2016). Toward principles of historical ecology By casting a wide net across space and time and integrating across disciplines, historical ecology is uniquely situated to provide novel insights into complex system dynamics and change in the Anthropocene. We argue that historical ecology's uniquely integrated approach and ability to provide novel insights across all scales of ecology make it more than a tool to "simply provide a means of extending the time frame" of ecological research (e.g., Vellend et al., 2013). Instead, shared general concepts and theories unite the discipline as a framework for research, analysis, and application. Looking forward, we identify the need to develop a conceptual framework that clearly defines the topical, spatiotemporal, and methodological scope of historical ecology along with widely accepted principles to standardize methods and sources, unite disparate studies, and maximize the application of findings (Fig. 2). We see a parallel evolution to that of landscape ecology, for which general principles coalesced in the 1990s (Wiens, 1992; Forman, 1995), or that of geographic information science (GIS) over the past two decades as emphasis has shifted from GIS as a "tool" or "system" to a "science" (Goodchild, 2010). Figure 2Open in figure viewerPowerPoint Conceptual framework illustrating the scope of historical ecology. Historical ecology encompasses historical ecosystem characteristics (bottom right), biophysical setting and processes (bottom left), and the interaction of humans with their environment (top); time (both past states and change) is implicit across all. So what might historical ecology principles look like? They might address human–environment interactions and feedbacks, define the scope of "history" in the context of ecological change, delineate the spatial and temporal scale and resolution of historical ecology studies and temporal continuity, address the importance of place, address theories of ecological and landscape transformation and disturbance, and reflect on its application to current and future ecosystems, to name a few. These principles can draw inspiration from existing ecological principles, such as principles of landscape change and scale from landscape ecology (Forman, 1995) or of land-use management (Dale et al., 2000). Principles could range from the extremely simple (e.g., "Ecosystems change through time" or "Humans are important, often dominant, drivers of disturbance") to complex concepts that address historical continuity and ecological memory (e.g., "Ecological landscape patterns at a given time are reflective of landscape and land-use history, setting, and biological interactions"). In developing principles of historical ecology, the challenge will be how to retain the "big tent" flexibility that historical ecology currently offers—that accommodates multiple perspectives, disciplines, and approaches—while articulating and honing a shared conceptual framework. Such principles could provide a backbone for subsequent historical ecology research, education, and application, setting the stage for helping all of us anticipate and manage for ongoing and future environmental change. ACKNOWLEDGEMENTS The authors thank three anonymous reviewers and Editor-in-Chief Pamela Diggle for their helpful comments on an earlier version of this manuscript. LITERATURE CITED Beller, E. E., P. Downs, R. M. Grossinger, B. K. Orr, and M. N. Salomon. 2016. From past patterns to future potential: Using historical ecology to inform river restoration for an intermittent California river. Landscape Ecology 31: 581– 600. Crumley, C. L. 2003. Historical ecology: Integrated thinking at multiple temporal and spatial scales. In World System History and Global Environmental Change, 2003, Lund University, Lund, Sweden. Available at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.554.2791&rep=rep1&type=pdf. Dale, V. H., S. Brown, R. A. Haeuber, N. T. Hobbs, N. Huntly, R. J. Naiman, W. E. Riebsame et al. 2000. Ecological principles and guidelines for managing the use of land. Ecological Applications 10: 639– 670. Egan, D., and E. A. Howell. 2001. The historical ecology handbook: A restorationist's guide to reference ecosystems. Island Press, Washington D.C., USA. Forman, R. T. 1995. Some general principles of landscape and regional ecology. Landscape Ecology 10: 133– 142. Goodchild, M. F. 2010. Twenty years of progress: GIScience in 2010. Journal of Spatial Information Science 1: 3– 20. Grossinger, R. 2012. Napa Valley historical ecology atlas: Exploring a hidden landscape of transformation and resilience. University of California Press, Berkeley, California, USA. Higgs, E., D. A. Falk, A. Guerrini, M. Hall, J. Harris, R. J. Hobbs, and W. Throop. 2014. The changing role of history in restoration ecology. Frontiers in Ecology and the Environment 12: 499– 506. McClenachan, L., A. B. Cooper, M. G. McKenzie, and J. A. Drew. 2015. The importance of surprising results and best practices in historical ecology. BioScience 65: 932– 939. Raby, M. 2015. Ark and archive: Making a place for long-term research on Barro Colorado Island, Panama. Isis 106: 798– 824. Rhemtulla, J. M., and D. J. Mladenoff. 2007. Why history matters in landscape ecology. Landscape Ecology 22: 1– 3. Rosenberg, A. A., W. J. Bolster, K. E. Alexander, W. B. Leavenworth, A. B. Cooper, and M. G. McKenzie. 2005. The history of ocean resources: Modeling cod biomass using historical records. Frontiers in Ecology and the Environment 3: 84– 90. Sanderson, E. W. 2009. Mannahatta: A natural history of New York City. Abrams, New York, New York, USA. Swetnam, T. W., C. D. Allen, and J. L. Betancourt. 1999. Applied historical ecology: Using the past to manage for the future. Ecological Applications 9: 1189– 1206. Szabó, P. 2014. Historical ecology: Past, present and future. Biological Reviews of the Cambridge Philosophical Society 90: 997– 1014. Trant, A., W. Nijland, K. Hoffman, D. L. Mathews, D. McLaren, T. A. Nelson, and B. M. Starzomski. 2016. Intertidal resource use over millennia enhances forest productivity. Nature Communications 7: 12491. Vellend, M., C. D. Brown, H. M. Kharouba, J. L. McCune, and I. H. Myers-Smith. 2013. Historical ecology: Using unconventional data sources to test for effects of global environmental change. American Journal of Botany 100: 1294– 1305. Wiens, J. 1992. What is landscape ecology, really? Landscape Ecology 7: 149– 150. Wolkovich, E. M., B. I. Cook, K. K. McLauchlan, and T. J. Davies. 2014. Temporal ecology in the Anthropocene. Ecology Letters 17: 1365– 1379. Citing Literature Volume104, Issue5May 2017Pages 645-648 This article also appears in:The "On the Nature of Things" Essays: New Ideas and Directions in Botany FiguresReferencesRelatedInformation