This chapter summarizes the most prominent abiotic components of recent climate change to establish the environmental context from which the discussion in the rest of the book proceeds. As will become clear in subsequent chapters, the rapid pace and broad geographic extent of abiotic changes reviewed here cannot be viewed in isolation for, as important as they are as drivers of ecological dynamics, in many if not most cases the ecological responses resulting from them owe to an alteration of biotic interactions. As an example we may consider the recent mass abandonment of retreating ice floes by Pacific walrus along...

The previous chapter focused on the past 150 years of climate change, which I referred to as recent and rapid climate change. Foreseeing the ecological consequences of the expected climatic changes that are projected to occur over the next century is an exceedingly complex undertaking. As suggested elsewhere (Post and Forchhammer 2006), however, it may be possible to garner insights into the potential consequences of future rapid climate change by considering the dynamics of plant and animal species and species assemblages during the Earth’s most recent period of rapid warming.

Examination of the faunal assemblages of the Pleistocene reveals details...

An individual’s life history comprises progressive stages in its development, maturation, reproduction, and eventual mortality. A suite of traits is associated with this progression. Traits typically of interest in a life history are the timing of emergence, hatching, or birth; size or length at emergence, hatching, or birth; timing of the annual period of reproduction; age or size at which the onset of reproduction occurs; age or size at which reproduction ceases; and age or size at the time of death. The study of the timing of life history events and the manner in which they vary in space and...

As a starting point in what will develop into a rather lengthy treatment of the related subjects of population dynamics and stability in relation to climate change, let us consider a deceptively simple illustration of the notion of stable point equilibrium in population dynamics (figure 4.1a). This figure derives from the now classic treatment of stability in deterministic and fluctuating environments by May (1973b). In it, we observe that the densities of two populations, N₁ and N₂, have settled into equilibrium with one another and remain locked in this arrangement because of the strongly stabilizing influence of the compression factor,...

One of the earliest applications of niche theory in quantitative ecology addressed the seemingly simple question of the extent to which the niches of two species can overlap and allow co-occurrence or coexistence of the species (May and MacArthur 1972). This question grew out of the then recent development of the notions of limiting similarity and niche packing, according to which coexistence among species with similar resource requirements was assumed to be promoted through minimization of niche overlap through divergence in habitat utilization patterns or character displacement (MacArthur and Levins 1964, 1967). The answer is highly relevant in the context...

Returning briefly to the starting point in chapter 4, we are reminded that, in May’s simple two-species community, stability was achieved through interaction between the two species in a deterministic environment, but was potentially eroded by environmental variability. Although not presented as such, this is representative of the tension hypothesis, in which biotic interactions counteract abiotic influences on the stability of the biological system.

In this chapter we will explore in greater detail the implications of climate change for community composition, dynamics, and stability and examine further examples in which climatic variability mediates interactions among species, in some cases degrading...

Spawning what has since become a major subdiscipline within ecology, Elton inserted a subtle statement near the end of his landmark book on invasions in ecology (Elton 1958). In the penultimate chapter of that book, titled “The Reasons for Conservation,” which sets the stage for the final chapter, “The Conservation of Variety,” Elton commented, in passing, on the importance of complexity for ecosystem stability, speculating that more simple communities would likely be more vulnerable to disturbance. The relationship between species diversity and ecosystem function and stability is currently one of the most intensely studied topics in ecology. This subject is...

Through their interactions with each other and with the abiotic environment, organisms transport energy and mineral nutrients within and among communities, across landscapes and the surface-subsurface boundary, between terrestrial and aquatic or marine environments, and between the biosphere and the atmosphere. At any stage along the multiple pathways of energy and nutrient exchange, climate change may act to alter the strengths of these interactions. The ecosystem is the most comprehensive interactive framework in ecology and, perhaps for this reason, difficult to conceptualize in a consistent manner. Consider, for instance, the two heuristic representations in figure 8.1. The first depicts the...

Earth’s climate is warming at a pace that may very well be unprecedented, and it is doing so from a higher baseline average temperature than that which was the starting point for the most recent episode of rapid warming, which signaled the end of the pleistocene and the demise of most of its large mammals. That most recent warming episode also coincided with geographically widespread biome shifts. Perhaps more tellingly, current warming, still in its early stages, has already heralded similarly geographically widespread and taxonomically broad shifts in phenological dynamics, population dynamics, species distributions, and ecosystem carbon dynamics. We may...