Cross-scale interactions, nonlinearities, and forecasting catastrophic events

Abstract

Catastrophic events share characteristic nonlinear behaviors that are often generated by cross-scale interactions and feedbacks among system elements. These events result in surprises that cannot easily be predicted based on information obtained at a single scale. Progress on catastrophic events has focused on one of the following two areas: nonlinear dynamics through time without an explicit consideration of spatial connectivity [Holling, C. S. We provide an interdisciplinary, conceptual, and general mathematical framework for understanding and forecasting nonlinear dynamics through time and across space. We illustrate the generality and usefulness of our approach by using new data and recasting published data from ecology (wildfires and desertification), epidemiology (infectious diseases), and engineering (structural failures). We show that decisions that minimize the likelihood of catastrophic events must be based on cross-scale interactions, and such decisions will often be counterintuitive. Given the continuing challenges associated with global change, approaches that cross disciplinary boundaries to include interactions and feedbacks at multiple scales are needed to increase our ability to predict catastrophic events and develop strategies for minimizing their occurrence and impacts. Our framework is an important step in developing predictive tools and designing experiments to examine cross-scale interactions. N onlinear interactions and feedbacks across spatial scales and their associated thresholds are common features of biological, physical, and materials systems (1-3). These spatial nonlinearities and emergent behaviors challenge the ability of scientists and engineers to understand and predict system behavior at one scale based on information obtained at finer or broader scales (3, 4). Cross-scale interactions often result in ''surprises'' with severe consequences for the environment and human welfare (5). For example, wildfire initiated by a single lightning strike can spread nonlinearly across large forested landscapes as a result of positive feedbacks between weather, fire behavior, and vegetation pattern, with significant impacts on ecosystem function, local and regional economies, and human health (6). Similarly, the devastating impact of a relatively small piece of foam (Ͻ0.3 m 2 ) initiated a series of reactions that cascaded very rapidly and nonlinearly to result in the break up of the Columbia space shuttle within minutes after the initial temperature increase (7).In this article, we introduce a general framework for understanding the occurrence and consequences of system interactions that cross scales in space and time (Fig. 1). Our goal is to identify the conditions leading to catastrophic events to minimize the impacts of these events on ecosystem services, atmospheric conditions, and human welfare. The significance of thresholds and feedbacks is gaining recognition in various disciplines (3, 8, 9). However, the key to understanding threshold behavior through time necessitates the incorpor...

Regional vegetation die-off in response to global-change-type drought

“…Our results highlight how drought-induced die-off can span across the range of a vegetation type and challenges the current paradigm for climate-induced vegetation dynamics, which focuses largely on changes at the margins of a species' range and the ecotone boundaries within that range (1,5,6). Additionally, if temperatures continue to warm, vegetation die-off in response to future drought may be further amplified (5,8,9,12). This recent drought episode in southwestern North America may be a harbinger of future global-change-type drought throughout much of North America and elsewhere, in which increased temperature in concert with multidecadal drought patterns associated with oceanic sea surface oscillations can drive extensive and rapid changes in vegetation and associated land surface properties.…”

“…Such rapid shifts in vegetation may represent abrupt, rapid, and persistent shifts in not only ecotones, but also in dominant vegetation cover and associated ecosystem process (5,(7)(8). At a minimum, the spatially extensive die-off will need to be considered in regional environmental assessments and management decisions over the next several decades, the shortest interval required for a P. edulis-dominated overstory structure to reestablish.…”

“…At a minimum, the spatially extensive die-off will need to be considered in regional environmental assessments and management decisions over the next several decades, the shortest interval required for a P. edulis-dominated overstory structure to reestablish. More generally, an improved predictive capability to forecast ecological responses to climate at regional scales is needed to effectively deal with the consequences of large-scale, long-term climate forcings (2,8). Our results highlight how drought-induced die-off can span across the range of a vegetation type and challenges the current paradigm for climate-induced vegetation dynamics, which focuses largely on changes at the margins of a species' range and the ecotone boundaries within that range (1,5,6).…”

“…Indeed, the most recent protracted drought in southwestern North America, spanning the beginning of the 2000 millennium, exhibited anomalous sea surface temperature patterns consistent with projections of global change response (3). Protracted drought can trigger large-scale landscape changes through vegetation mortality from water stress (5, 6), sometimes associated with bark beetle infestations (5), but the potential for regional to subcontinental scale vegetation die-off under global-change-type drought remains a pivotal uncertainty in projections of climate change impacts (1,7,8). Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades.…”

Regime shifts and resilience in China’s coastal ecosystems

“…Yet, the internal feedbacks within each shift, and their connections with each other, suggest that synergistic effects could lead to large-scale regime shifts. The feedbacks that stabilize alternative states are not constant; they can change through time, which in theory can facilitate new shifts when the feedback changes (Peters et al 2004;Yelenik and D'Antonio 2013). Evidence for regime shifts in the highly sensitive, fast-responding coastal ecosystems suggests that some linked elements of the larger system have already been altered.…”