Ecologists addressed the effects of disturbances from the onset of the field by focusing on ecesis, which is the process by which organisms migrate and establish under the environmental conditions ...created by disturbances. Ecesis is the onset of succession, a self-organizing process whose nature, speed, and outcome depend in part on the outcomes of ecesis and the residual legacies remaining after disturbances. A by-product of succession after a disturbance is the reorganization of species dominance, or novelty. The degree of novelty in the outcome increases with the severity of the disturbance event. Initially, ecologists focused mostly on non-anthropogenic disturbances, but as human activity intensified and became a global force, more attention was given to the effects of anthropogenic disturbances on ecosystems. Today, anthropogenic and non-anthropogenic disturbances and their interactions are increasingly affecting ecosystems, particularly those exposed to extreme disturbance events. Extreme disturbance events are complex and low probability events composed of several disturbance forces that individually and in synergy affect different sectors of ecosystems, including the conditions that drive ecesis. I review the literature on disturbance research including the effects of extreme disturbance events on social–ecological–technological systems (SETSs). A SETS is an ecosystem defined by the flow and accumulation of energy through the medium of organisms, constructed infrastructure, institutions, and their environment. Human intentions, values, and capacities are part of the functioning of SETS, and they can drive ecological processes as do non-anthropogenic forces. Moreover, human-directed activities after an extreme disturbance event affect whole landscapes. The passage of hurricane María over the Puerto Rico SETS established that extreme disturbance events are of such power and complexity that they can influence the level and kind of relationship between humans and the environment, including the structure and species composition of the ecological systems within SETS. However, extreme disturbance events such as hurricanes have not changed the successional trajectory originally impulsed by anthropogenic disturbances. Thus, the species composition and functioning of novel forests in Puerto Rico are tied to economic activity in the social and technological sectors of SETS. It is no longer possible to interpret ecosystem functioning without considering the synergy between anthropogenic and non-anthropogenic extreme disturbances.
Forestry in the Anthropocene Lugo, Ariel E
Science,
2015-Aug-21, 2015-08-21, 20150821, Letnik:
349, Številka:
6250
Journal Article
Recenzirano
Odprti dostop
Human activity has had enormous effects on the species composition of floras and faunas, creating new ecological biomes worldwide. A principal challenge in forestry research and conservation is how ...to deal with these novel ecosystems. Most attention to this phenomenon is centered on the negative effects of species introductions and the need to stem the tide of species invasion. However, we need to scientifically understand new ecosystems and learn to recognize adaptive species combinations that will function sustainably in changing environmental conditions.
An extreme disturbance event is one in which any of its component disturbance forces and their interactions with affected systems have dimensions and responses that exceed the known range of ...variation expected of those parameters. If the exposed system does not respond or exhibits a low level response to an event, the event was not extreme to the exposed system, regardless of the dimensions of its disturbance forces. Extreme disturbance events are complex and require disaggregation to improve understanding of their effects. The areas affected by extreme events and the duration of the events are related but involve many orders of magnitude in terms of area affected and duration. One way to compare events is through a common and objective unit of measure such as energy. A comparison of ten extreme events in terms of their power and total energy delivered per unit area revealed a broad range of values among them. The power of events ranged 8 orders of magnitude and the total load per unit area ranged 14 orders of magnitude. Each event had different points of interaction with exposed ecosystems. When exposed to the same extreme event, the response of social systems is different from the response of the ecological systems. Also, social systems recovered quicker to a category 3 hurricane than did ecological systems. Both social and ecological systems have the capacity to evolve, adapt, innovate, and develop novelty in response to the selective pressure of extreme events.
In the wake of widespread loss of old-growth forests throughout the tropics, secondary forests will likely play a growing role in the conservation of forest biodiversity. We considered a complex ...hierarchy of factors that interact in space and time to determine the conservation potential of tropical secondary forests. Beyond the characteristics of local forest patches, spatial and temporal landscape dynamics influence the establishment, species composition, and persistence of secondary forests. Prospects for conservation of old-growth species in secondary forests are maximized in regions where the ratio of secondary to old-growth forest area is relatively low, older secondary forests have persisted, anthropogenic disturbance after abandonment is relatively low, seed-dispersing fauna are present, and old-growth forests are close to abandoned sites. The conservation value of a secondary forest is expected to increase over time, as species arriving from remaining old-growth forest patches accumulate. Many studies are poorly replicated, which limits robust assessments of the number and abundance of old-growth species present in secondary forests. Older secondary forests are not often studied and few long-term studies are conducted in secondary forests. Available data indicate that both old-growth and second-growth forests are important to the persistence of forest species in tropical, human-modified landscapes.
In 1966 Eugene P. Odum delivered a speech before the Ecological Society of America that transformed the way ecologists looked at succession. His comparison of mature and successional systems lead ...ecologists to place secondary forests in an inferior position relative to mature ones to the point that today, prominent tropical biologists argue for and against the conservation value of secondary forests. Nevertheless, we live in the era of secondary forests that is rapidly giving way to a new era of novel tropical forests. Research in Puerto Rico documents the emergence of novel forests, which are different in terms of species composition, dominance, and relative importance of species from forests that were present before the island was deforested. These novel forests emerged without assistance. They are a natural response to the new environmental conditions created by human activity. Natural processes have remixed or reassembled native and introduced plant and animal species into novel communities adapted to anthropogenic environmental conditions. Novel forests are expected to protect soils, cycle nutrients, support wildlife, store carbon, maintain watershed functions, and mitigate species extinctions. The dawn of the age of tropical novel forests is upon us and must not be ignored.
Invasive species, disease vectors, and pathogens affect biodiversity, ecosystem function and services, and human health. Climate change, land use, and transport vectors interact in complex ways to ...determine the spread of native and non-native invasive species, pathogens, and their effects on ecosystem dynamics. Early detection and in-depth understanding of invasive species and infectious diseases will require an integrated network of research platforms and information exchange to identify hotspots of invasion or disease emergence. Partnerships with state and federal agencies that monitor the spread and impacts of invasive species and pathogens will be critical in developing a national data and research network that can facilitate a full understanding of the resulting effects on ecosystems and society. Citizen science can also play a role; individuals can report new invasions, record phenological changes associated with invasions or disease outbreaks, and can participate in efforts such as the Breeding Bird Survey, which may reveal long-term biotic change following species invasions and disease spread. The ecological and societal impacts of invasive species and pathogens differ across gradients of climate and land use, and in the presence of global climate change may exacerbate both their propagation and impacts. Understanding the interactions of invasive species, disease vectors, and pathogens with other drivers of ecosystem change is critical to human health and economic well-being.
The reality confronting ecosystem managers today is one of heterogeneous, rapidly transforming landscapes, particularly in the areas more affected by urban and agricultural development. A landscape ...management framework that incorporates all systems, across the spectrum of degrees of alteration, provides a fuller set of options for how and when to intervene, uses limited resources more effectively, and increases the chances of achieving management goals. That many ecosystems have departed so substantially from their historical trajectory that they defy conventional restoration is not in dispute. Acknowledging novel ecosystems need not constitute a threat to existing policy and management approaches. Rather, the development of an integrated approach to management interventions can provide options that are in tune with the current reality of rapid ecosystem change.
We explore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and ...inadvertent introduction of species from other regions. Novel ecosystems (also termed 'emerging ecosystems) result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or 'wild' ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches.
Don't judge species on their origins Davis, Mark A; Chew, Matthew K; Hobbs, Richard J ...
Nature,
06/2011, Letnik:
474, Številka:
7350
Journal Article
Recenzirano
Odprti dostop
By this point, partly fuelled by Elton's book, proponents of biodiversity preservation and ecological restoration commonly used military metaphors and exaggerated claims of impending harm to help ...convey the message that introduced species are the enemies of man and nature. ... the introduction of non-native species has almost always increased the number of species in a region5.
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