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This chapter discusses the role of climate variability and change and their effects on the marine environment. As the frequency of physical forcing increases, the biological changes progress from local effects on individuals at synoptic weather scales, towards regional effects on population dynamics at monthly to decadal scales, and over and across basins on systems ecology at multidecadal timescales and longer. The nature of the impact is size‐ and age‐dependent with generally greater and more rapid impacts on the smaller and younger individuals. The use of large‐scale climate indices to link climate forcing with ecological responses is highlighted as are the insights gained through comparative studies between ecosystems or between fish populations that inhabit different hydrographic regimes.

This chapter discusses current urban land use (form, size, and shape of cities and urban areas) against a global background. The specifics of urban land use (surface characteristics, dynamics of change, impacts on the environment) are examined using different conceptual approaches (e.g., ecosystem services, risk, and governance aspects). Although urban land use is a special case (i.e., small in scale, yet dominant in influence), a range of commonalities exist between urban and nonurban land use. A discussion on shrinking cities underlines that there are more pathways to urban land development than growth. The current extent and rates of urbanization force us to rethink land connectivity, competition, and decision making; the resulting knowledge can be used to generate a new concept of land use. The connections and implications of urban land-use patterns need to be examined on a global scale, as local-scale patterns may be affected by global-scale outcomes and vice versa. Published in the Strungmann Forum Reports Series.

Land issues are central to geopolitics, economics, globalization, human well-being, and environmental sustainability. There is concern that not enough land will be available to meet societal and ecosystem needs of the projected global population by the middle of the 21^st century. Three trends are currently reshaping land use locally and globally: urbanization, the integration of economies and markets, and the emergence of new land-use agents. The prevailing transition toward urban livelihoods results in changes in lifestyle, diet, and land use. Although distant societies have been connected for centuries through trade, the 21st century will be characterized by an acceleration of simultaneously occurring, global-reaching changes: increases in real-time information and communication, large-scale investments, massive rural to urban migration, climate change, and other environmental changes. This chapter discusses urban land teleconnections and proposes the need for conceptual framework to address the tension between the need to use land for societal benefits and the need to conserve land. Published in the Strungmann Forum Reports Series.

Rising demand for land-based products as well as conservation of forests and carbon sinks create increasing competition for land. Land-use competition has many drivers, takes different forms, and can have many significant implications for ecosystems as well as societal well-being. This chapter discusses the effect of increased demand for nonprovisioning ecosystem services (biodiversity conservation and carbon sequestration), urbanization, bioenergy, and teleconnections. Three major types of land-use competition are discerned: production versus production (e.g., food vs. fuel), production versus conservation (e.g., food production vs. conservation), and built-up environment versus production or conservation (e.g., food vs. urban). Sustainability impacts that result from land-use competition are analyzed and found to differ strongly between the different types of land-use competition. They are associated with important trade-offs and high uncertainty. Institutional aspects related to land-use competition are discussed using a conceptual model that distinguishes types of institutions as well as their functions. Analysis of long-term trajectories suggests that land-use competition is likely to intensify in the medium- to long-term future, mainly in the face of expected scarcities in resource supply, mitigation and adaptation policies related to climate change, and climate change impacts and demographic pressures. Major research gaps are discussed and priority research topics outlined. Published in the Strungmann Forum Reports Series.

The climate is changing from human activities. This has major implications for the future and for human society and ecosystems, including birds. However, it is often masked by natural variability and there is great weather-related variability. This chapter reviews observed changes in climate, with a focus on changes in surface climate including variations in major patterns (modes) of climate variability and teleconnections. Of particular importance are changes in extremes. It describes how natural and anthropogenic drivers of climate change are assessed using climate models and concludes with a brief summary of future projected changes in climate and their impacts.

El Niño events are the most powerful of natural climate variations, rearranging weather patterns around the world and triggering countless extreme events. This chapter gives an overview of El Niño, its history and its physics, including its important effect on the Pacific jet stream. El Niño is the main source of information for the science of seasonal forecasting, which is also introduced here.

The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula (WAP) region, which is the location of the Palmer LTER (figure 9.1), provide the opportunity to observe how climate-driven variability in the physical environment is related to changes in the marine ecosystem (Ross et al. 1996; Smith et al. 1996; Smith et al. 1999). This is a sea ice–dominated ecosystem where the annual advance and retreat of the sea ice is a major physical determinant of spatial and temporal change in its structure and function, from total annual primary production to the breeding success and survival of seabirds. Mounting evidence suggests that the earth is experiencing a period of rapid climate change, and air temperature records from the last half century confirm a statistically significant warming trend within the WAP during the past half century (King 1994; King and Harangozo 1998; Marshall and King 1998; Ross et al. 1996; Sansom 1989; Smith et al. 1996; Stark 1994; van den Broeke 1998; Weatherly et al. 1991). Air temperature–sea ice linkages appear to be very strong in the WAP region (Jacka 1990; Jacka and Budd 1991; King 1994; Smith et al. 1996; Weatherly et al. 1991), and a statistically significant anticorrelation between air temperatures and sea ice extent has been observed for this region. Consistent with this strong coupling, sea ice extent in the WAP area has trended down during this period of satellite observations, and the sea ice season has shortened. In addition, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests possible linkages among sea ice, cyclonic activity, and global teleconnections.

The El Nino–Southern Oscillation (ENSO) is one of the most important contributors to interannual variability on Earth (Diaz and Markgraf 2000). It is an aperiodic phenomenon that tends to reoccur within the range of 2 to 7 years, and it is manifest by the alternation of extreme warm (El Niño) and cold (La Niña) events. There is also evidence (Allen 2000) that the aperiodic ENSO phenomenon must be considered in conjunction with climate fluctuations at decadal to multidecadal time frames that may modulate ENSO’s lower frequency variability. Numerous studies show global climatic impacts associated with the ENSO phenomenon. Further, there is considerable evidence to indicate that ENSO impacts the climate of both middle and high latitudes, and a recent analysis (figure S.1, discussed below) provides a global picture of warm versus cold ENSO conditions. Consequently, it is not surprising that many LTER sites, from the Arctic to Antarctic, show evidence of ENSO-related fluctuations in environmental variables. The quasi-quintennial timescale of variability is second only to seasonal variability in driving worldwide weather patterns. Consequently, an important theme in part II is the worldwide influence of ENSO-related climate variability and the teleconnected spatial patterns of this variability. Also, a common theme for several ecosystems discussed in this section is their high sensitivity to small climatic changes that are subsequently amplified and cascaded through the system. For example, the narrow temperature threshold for an ice-to-water phase change may create a pronounced nonlinear ecosystem response to what is a relatively small temperature shift (as demonstrated for the McMurdo Dry Valleys). Or alternatively, this narrow temperature threshold may shift a sea ice–dominated ecosystem (Palmer LTER) to a more oceanic marine ecosystem by reducing the seasonality and magnitude of the sea ice habitat. Such nonlinear amplifications of small climatic changes can increase the ecological response and make it more detectable within the natural background of variability. We explore these themes here. To illustrate the global footprint of ENSO variability, composites of yearly averaged El Niño and La Niña conditions for surface air temperature (SAT) and sea surface temperature (SST, Reynolds and Smith 1994) were generated.

Interdecadal-scale climate variability must be considered when interpreting climatic trends at local, regional, or global scales. Significant amounts of variance are found at interdecadal timescales in many climate parameters of both “direct” data (e.g., precipitation and sea surface temperatures at specific locations) and “indirect” data through which the climate system operates (e.g., circulation indices such as the Pacific North American index [PNA] or the North Atlantic Oscillation index [NAO]). The aim of this study is to evaluate LTER climate data for evidence of interdecadal-scale variability, which may in turn be associated with interdecadal-scale fluctuations evident in ecological or biophysical data measured throughout the LTER site network. In their conceptualization of climatic variability, Marcus and Brazel (1984) describe four types of interannual climate variations: (1) Periodic variations around a stationary mean are well known to occur at short timescales, such as diurnal temperature changes or the annual cycle, but are difficult to resolve at decadal or longer timescales. (2) Discontinuities generated by sudden changes in the overall state of the climate system can reveal nonstationarity in the mean about which data vary in a periodic or quasi-periodic manner. These sudden alterations can result in periods perhaps characterized by prolonged drought or colder than normal temperatures. (3) The climate system may undergo trends such as periods of slowly increasing or decreasing precipitation or of warming or cooling until some new mean “steady” state is reached. (4) Climate data may exhibit increasing or decreasing variability about a specific mean value or steady state. Interdecadal contributions to climate variability can be described in terms of types 2 and 3 of Marcus and Brazel’s conceptual classification—discontinuities in the mean and trends in the data. Records of the Northern Hemisphere’s average land surface temperature show discontinuities in the mean state of the hemispheric temperature record in conjunction with obvious trends. Conceptually, it is hard to distinguish between these aspects of climate variability. Trends are an essential component of an alteration in the mean state of the temperature series, as they serve as a temporal linkage between the different mean states.

When temporally smoothed data are used for the period 1925 to 1985 there is a close inverse statistical relationship acting at an interdecadal timescale between the Pacific Northwest (PNW) air temperatures and Coho salmon catch off the coast of Washington and Oregon. This relationship is now well known, although not fully explained, but at the time of its discovery in 1994 it was part of advances being made by several research groups on interdecadal-scale climate/ecological changes in the PNW (Greenland 1995). The discovery and later, related findings may be usefully examined within the context of the framework questions of this book (see chapter 1) because it provides a very interesting example of climate variability and ecosystem response found, in part, by Long-Term Ecological Research (LTER) investigators. The logical progression for this chapter is first to review a little of the relationship between Coho salmon and climate and then to explain how a study at one LTER site led to a finding with regional implications. An update of the findings at interdecadal-scale climate/ecological changes in the PNW is then appropriate, followed by a discussion of the topic with the framework questions of this book. The PNW is defined, for the purposes of this chapter, as the area of Washington and Oregon west of the crest of the Cascade Range. The term decadal is used loosely in this chapter to refer to changes that focus on time periods of about 10 to 30 years in length. Salmon live part of their lives in terrestrial, freshwater environments and part in marine, saltwater environments. The salmon life history starts with fertilized eggs remaining in gravel in freshwater stream beds and hatching after 1–3 months. One to five months later, fry emerge in the spring or summer. Juvenile fish are in freshwater from a few days to 4 years, depending on species and locality. After the juveniles change to smolts, they can migrate to the ocean, usually in spring or early summer, often taking advantage of streamflows driven by snowmelt. The fish spend 1–4 years in the ocean and then return to their freshwater home stream to spawn and die. More specifically, the typical life cycle for Oregon Coho spans 3 years (18 months in freshwater and 18 months in the ocean).