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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. [ABSTRACT FROM AUTHOR]

We review literature relevant to assessing the future of tropical forests and supplement the review with new data from the lowlands of Venezuela. Compared to today, future tropical forests will have a higher level of novelty, defined as the degree of dissimilarity of a system relative to a historical baseline. Processes of succession and evolution generate novelty in forests and have done so for millennia. Under increasing human activity and climate change, the rate of generation of novelty has increased and the resulting forests are termed novel forests to distinguish them from historical forests. Historical forests are less exposed to anthropogenic disturbances and operate at slower levels of novelty generation. Acclimation, adaptation, changes in species composition and dominance, and changes in the proportions of species in communities are the responses of the biota to climate change and anthropogenic disturbances. Therefore, novelty contributes to the persistence of tropical forests in spite of increasing levels of human activity. Novel forests are similar to historical forests in terms of structure but they are younger, they have a faster turnover of mass and chemical elements, and different species composition. Historical species assemblages cannot cope with the altered environments that result from chronic anthropogenic disturbances. The dominant species in novel forests tend to be, and function as, pioneer species. High levels of species dominance in novel forests influence the proportions of chemical elements, which when coupled to species traits and attributes, help explain how novel forests cope with the conditions that result from anthropogenic activities. Novelty is more common in the tropics than in other latitudinal regions, and within the tropics, it is more common in islands where human activity is more intense than in continents. Novel tropical forests in islands have greater representation and dominance of introduced species than novel forests in continents, where native species with wide geographic distributions dominate. Regardless of geography, novel tropical forests share similar attributes and functioning. The adaptability of novel forests to extreme conditions created by human activity signals a future for tropical forests that is different from predictions of constant degradation, homogenization, and loss of biodiversity. Instead, a process of recombination of species (all taxa) into new species assemblages maintains structure, function, physiognomy, species richness, and ecological services. This remixing initially involves loss of large organisms, certain groups of species, and loss of old-growth attributes of forests. Some of these losses can be reversed through succession, assuming there is sufficient time to restore depleted stores such as soil organic matter. Continued environmental change will stimulate continued remixing of species, loss of vulnerable species, gains of less vulnerable ones, and more dissimilarity with historical forests. Novel forests are an answer to the changes induced by climate change and other anthropogenic disturbances, and as such require conservation measures, because as they mature, novel forests usually diversify and help restore lost biodiversity. We also review strategies to conserve biodiversity and optimize ecological services using novel forest succession. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This essay addresses the conservation issues facing mangroves in the Anthropocene, defined as the era of human domination over the world. We review the laws, policies, international agreements, and local actions that address the conservation of mangrove forests in the Neotropics and relate them to the Anthropocene. Collaboration between governments, non-governmental organizations, and communities that depend on mangroves for their livelihood will be critical in the Anthropocene. The essay also reviews recent developments in mangrove ecology and ecophysiology that enlighten how mangroves might respond to changes in temperature and rainfall, sea level rise, and other anthropogenic and natural disturbances. Mangroves in the Anthropocene will also face changes in their species composition given the current movement of mangroves species across continental barriers as a result of human activity. These trends will lead to novel mangrove forests and in some cases expand the range of mangroves worldwide. The solution to mangrove persistence in the Anthropocene is not to isolate mangroves from people, but to regulate interactions between mangroves and humans through effective management. We will also have to expand the scope of the ecological analysis of mangrove ecosystems to include the social forces converging on the mangroves through an analytical approach that has been termed Social Ecology. [ABSTRACT FROM AUTHOR]

Aim Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple-stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance. Location Guánica Forest, Puerto Rico. Methods Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics. Results Direct effects of the hurricane were minimal, with stem mortality at < 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high – over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (> 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species. Main conclusions Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi-stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short-term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds. [ABSTRACT FROM AUTHOR]

The network of experimental forests and ranges administered by the US Department of Agriculture Forest Service consists of 77 properties that are representative of most forest cover types and many ecological regions in the nation. Established as early as 1908, these sites maintain exceptional, long-term databases on environmental dynamics and biotic responses. Early research at these sites focused on silviculture, ecosystem restoration, and watershed management. Over time, many of the properties have evolved into a functional network of ecological observatories through common large-scale, long-term experiments and other approaches. Collaboration with other institutions and research programs fosters intersite research and common procedures for managing and sharing data. Much current research in this network focuses on global change and interdisciplinary ecosystem studies at local to global scales. With this experience in developing networks and compiling records of environmental history, the experimental forests and ranges network can contribute greatly to formation of new networks of environmental observatories. [ABSTRACT FROM AUTHOR]

The world has become urban; cities increasingly shape our worldviews, relation to other species, and the large-scale, long-term decisions we make. Cities are nature, but they need to align better with other ecosystems to avoid accelerating climate change and loss of biodiversity. We need a science to guide urban development across the diverse realities of global cities. This need can be met, in part, by shifts in urban ecology and its linkages to related sciences. This perspective is a "synthesis of syntheses", consolidating ideas from the other articles in the Special Section. It re-examines the role of urban ecology, and explores its integration with other disciplines that study cities. We conclude by summarizing the next steps in the ongoing shift in urban ecology, which is fast becoming an integral part of urban studies. [ABSTRACT FROM AUTHOR]

This paper builds on the expansion of urban ecology from a biologically based discipline—ecology in the city—to an increasingly interdisciplinary field—ecology of the city—to a transdisciplinary, knowledge to action endeavor—an ecology for and with the city. We build on this "prepositional journey" by proposing a transformative shift in urban ecology, and we present a framework for how the field may continue this shift. We conceptualize that urban ecology is in a state of flux, and that this shift is needed to transform urban ecology into a more engaged and action based field, and one that includes a diversity of actors willing to participate in the future of their cities. In this transformative shift, these actors will engage, collaborate, and participate in a continuous spiral of knowledge → action → knowledge spiral and back to knowledge loop, with the goal of co producing sustainable and resilient solutions to myriad urban challenges. Our framework for this transformative shift includes three pathways: (1) a repeating knowledge → action → knowledge spiral of ideas, information, and solutions produced by a diverse community of agents of urban change working together in an "urban sandbox"; (2) incorporation of a social–ecological–technological systems framework in this spiral and expanding the spiral temporally to include the "deep future," where future scenarios are based on a visioning of seemingly unimaginable or plausible future states of cities that are sustainable and resilient; and (3) the expansion of the spiral in space, to include rural areas and places that are not yet cities. The three interrelated pathways that define the transformative shift demonstrate the power of an urban ecology that has moved beyond urban systems science and into a realm where collaborations among diverse knowledges and voices are working together to understand cities and what is urban while producing sustainable solutions to contemporary challenges and envisioning futures of socially, ecologically, and technologically resilient cities. We present case study examples of each of the three pathways that make up this transformative shift in urban ecology and discuss both limitations and opportunities for future research and action with this transdisciplinary broadening of the field. [ABSTRACT FROM AUTHOR]

We ask how environmental justice and urban ecology have influenced one another over the past 25 years in the context of the US Long-Term Ecological Research (LTER) program and Baltimore Ecosystem Study (BES) project. BES began after environmental justice emerged through activism and scholarship in the 1980s but spans a period of increasing awareness among ecologists and environmental practitioners. The work in Baltimore provides a detailed example of how ecological research has been affected by a growing understanding of environmental justice. The shift shows how unjust environmental outcomes emerge and are reinforced over time by systemic discrimination and exclusion. We do not comprehensively review the literature on environmental justice in urban ecology but do present four brief cases from the Caribbean, Africa, and Asia, to illustrate the global relevance of the topic. The example cases demonstrate the necessity for continuous engagement with communities in addressing environmental problem solving. [ABSTRACT FROM AUTHOR]

Discusses the ecology of tropical dry forests. Emphasis on the plant component of the system; Seasonality and variability; Dry forest structure and function; Examination of the tropical dry forest in relation to people; Importance of the dry forest and the dry forest environment to people throughout the tropics.

This review deals with energy flow through wetland ecosystems in the broadest sense. Solar energy drives primary productivity and auxiliary energy sources include water flow, water level fluctuation, nutrient inputs, sediment transport, and geomorphologic structure (27). We present data in water-movement categories to illustrate effects of water flow on metabolism. Similarly we do not limit consideration of the role of consumers to that of secondary production, but rather review additional functions such as control of energy flow and the recycling of nutrients. We examined the data with the goal of identifying principles and concepts peculiar to wetlands or at least different from their aquatic and terrestrial counterparts. One of the constraints on interpreting the literature is terminological. Additional confusion about primary productivity values derives from the array of differing assumptions, methods of collection, and computation of results. [ABSTRACT FROM AUTHOR]

Examines the ecology of mangroves in Florida and Puerto Rico. Interaction between man and mangroves; Characteristics of the mangrove ecosystems; Uses of mangroves.

This article discusses the ecosystem rehabilitation in the tropics. Half of the world's forests, as well as the largest area of mature forest in the world, are located in the tropics. Tropical lands are, on average, 42 percent forested and support the world's most complex ecosystems. It is very difficult to control with certainty the direction of a rehabilitation project. This is particularly true of complex tropical ecosystems, where there are a staggering number of possible states and species compositions. Damage to tropical forestland can be derelict, deforested, or impoverished, and annual rainfall can vary tremendously among different areas, as can mean temperature and nutrient levels in soils. One model describing rehabilitation options in the Great Lakes region of the U.S. and Canada included four alternative pathways that also apply to tropical conditions. Restoration implies a return to the original state; further degradation involves a do-nothing approach by which the land continues to suffer chronic human and natural stress and replacement is independent of the original state and might lead the system further away from the original state, perhaps by adding desirable human-made features and suppressing undesirable ones. INSETS: Strategies for rehabilitating tropical forests.;A Model of Ecosystem Rehabilitation.

Recent assessments of areas of different tropical forest types and their corresponding stand volumes were used to calculate the biomass densities and total biomass of tropical forests. Total biomass was estimated at 205 x 109 tons, and weighted biomass densities for undisturbed closed and open broadleafforests were 176 and 61 tons per hectare, respectively. These values are considerably lower than those previously reported and raise questions about the role of the terrestrial biota in the global carbon budget. [ABSTRACT FROM AUTHOR]

Land rehabilitation is proposed as a management strategy to reverse the negative consequences of tropical deforestation and land degradation. We first de- fine the concepts associated with ecosystem modification-conversion, damage, and degradation-and those associated with ecosystem repair-restoration, rehabilitation, and reclamation. We then present a scheme of sustainable land use in the tropics, with illustrations of how rehabilitation and restoration activities fit into the overall scheme of the use of land. Because damaged lands cannot contribute effectively to sustained economic development, land rehabilitation is a necessary step for increasing the chances of attaining sustainability. Approaches for rehabilitating ecosystems are discussed, including the management of stressors and subsidies in relation to their point of interaction in the ecosystem. Finally, we illustrate the concepts of ecosystem rehabilitation of damaged, degraded, and derelict lands with examples of case studies from dry to humid life zones in island and continental situations throughout the tropics. The case studies demonstrate that opportunities for success exist, even with severely degraded lands, but a considerable amount of research remains to be done before we have a full understanding of the complexity of the task facing us. [ABSTRACT FROM AUTHOR]

In the online and printed version of this article a few lines of text and a figure are incorrect. The corrected text and figure are given below [ABSTRACT FROM AUTHOR]

An editorial is presented discussing the global ecological impact of human activity. Topics addressed include reference to the theories of the 1965 book "The Ecological Theater and the Evolutionary Play," by George E. Hutchinson, the characterization of the current phase of forest ecology as the anthropocene era, and calls for proactive responsibility to positively guide and protect ecosystems in this period.

The coexistence of hurricanes, coral reefs, and rainforests in the Caribbean demonstrates that highly structured ecosystems with great diversity can flourish in spite of recurring exposure to intense destructive energy. Coral reefs develop in response to wave energy and resist hurricanes largely by virtue of their structural strength. Limitedfetch also protects some reefs from fully developed hurricane waves.While storms may produce dramatic local reef damage, they appear to have little impact on the ability of coral reefs to provide food or habitat for fish and other animals. Rainforests experience an enormousincrease in wind energy during hurricanes with dramatic structural changes in the vegetation. The resulting changes in forest microclimate are larger than those on reefs and the loss of fruit, leaves, cover, and microclimate has a great impact on animal populations. Recoveryof many aspects of rainforest structure and function is rapid, though there may be long-term changes in species composition. While resistance and repair have maintained reefs and rainforests in the past, human impacts may threaten theirability to survive. [ABSTRACT FROM AUTHOR]

Urban activities and related infrastructure alter the natural patterns of stream physical and chemical conditions. According to the Urban Stream Syndrome, streams draining urban landscapes are characterized by high concentrations of nutrients and ions, and might have elevated water temperatures and variable oxygen concentrations. Here, we report temporal and spatial variability in stream physicochemistry in a highly urbanized watershed in Puerto Rico. The main objective of the study was to describe stream physicochemical characteristics and relate them to urban intensity, e.g., percent impervious surface cover, and watershed infrastructure, e.g., road and pipe densities. The Rio Piedras Watershed in the San Juan Metropolitan Area, Puerto Rico, is one of the most urbanized regions on the island. The Rio Piedras presented high solute concentrations that were related to watershed factors, such as percent impervious cover. Temporal variability in ion concentrations lacked seasonality, as did all other parameters measured except water temperature, which was lower during winter and highest during summer, as expected based on latitude. Spatially, stream physicochemistry was strongly related to watershed percent impervious cover and also to the density of urban infrastructure, e.g., roads, pipe, and building densities. Although the watershed is serviced by a sewage collection system, illegal discharges and leaky infrastructure are probably responsible for the elevated ion concentration found. Overall, the Rio Piedras is an example of the response of a tropical urban watershed after major sewage inputs are removed, thus highlighting the importance of proper infrastructure maintenance and management of runoff to control ion concentrations in tropical streams. [ABSTRACT FROM AUTHOR]

Abstract: We measured CO2 efflux from stems of seven subtropical tree species situated along an elevational gradient in the Luquillo Mountains, Puerto Rico and scaled these measurements up to the landscape level based on modeled and empirical relations. The most important determinants of ecosystem stem respiration were species composition and stem temperature. At a species scale, measured CO2 efflux per unit bole surface area at a given temperature was highest in the early successional species Cecropia schreberiana and lowest in species that inhabit high elevations such as Micropholis garciniifolia and Tabebuia rigida. Carbon dioxide efflux rates followed a diel pattern that lagged approximately 6h behind changes in sapwood temperatures. At an ecosystem scale, our simulation model indicates a decreasing trend of stem respiration rates with increasing elevation due to shifts in species composition, lower temperatures and reductions in branch surface area. The highest estimated stem respiration rates were present in the lowland tabonuco forest type and the lowest rates were present in the elfin forest type (mean 7.4 and 2.1MgCha−1 yr−1, respectively). There was slight temperature-induced seasonal variation in simulated stem respiration rates at low elevations, with a maximum difference of 19% between the months of February and July. Our results coincide well with those of Odum and Jordan [Odum, H.T., Jordan, C.F., 1970. Metabolism and evapotranspiration of the lower forest in a giant plastic cylinder. In: Odum, H.T., Pigeon, R.F. (Eds.), A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. U.S. Atomic Energy Commission, Oak Ridge, TN, pp. I165–I189] for the tabonuco forest type and extend their work by presenting estimates and spatial patterns of woody tissue respiration for the entire mountain rather than for a single forested plot. [Copyright &y& Elsevier]

The physiognomy of Caribbean dry forest is shorter, denser and contains a greater proportion of multi-stemmed trees than other neotropical dry forests. Our previous research, conducted after Hurricane Georges in 1998, has shown that dry forest trees sprout near the base following hurricane disturbance, even if the trees have not incurred structural damage. However, for these hurricane-induced sprouts to contribute to the physiognomy of the forest, they must grow and survive. We followed sprout dynamics and stem mortality on 1,407 stems from 1998, after Hurricane Georges, until 2005. The number of surviving sprouts and the proportion of sprouting stems decreased during the 7-year period, but the sprouting rate was still 3-fold higher and the proportion of sprouting stems 5-fold higher than before the hurricane. Mortality of non-sprouting stems (15.4%) was about the same as for sprouting stems (13.9%) after 7 years. The mean length of the dominant sprout surpassed 1.6 m by 2005, with over 13% of the dominant sprouts reaching subcanopy height. Sprout growth and survival varied among species. These results demonstrate that, despite some thinning, hurricane-induced sprouts survive and grow and that the unique physiognomic characteristic of Caribbean dry forests is related to hurricane disturbance. [ABSTRACT FROM PUBLISHER]

Long-term ecological research is particularly valuable for understanding disturbance dynamics over long time periods and placing those dynamics in a regional context. We highlighted three case studies from Long Term Ecological Research (LTER) Network sites that have contributed to understanding the causes and consequences of disturbance in ecological systems. The LTER Network significantly enhances the ability to study disturbance by (a) encompassing ecosystems subject to a wide range of disturbances, (b) providing a long-term baseline against which to detect change and measure ecosystem responses to disturbance, (c) permitting observation of slow or infrequent events, (d) facilitating the use of multiple research approaches, (e) providing a focus for modeling disturbance dynamics, and (f) contributing to land and resource management. Long-term research is crucial to understanding past, present, and future disturbance dynamics, and the LTER Network is poised to make continuing contributions to the understanding of disturbance. Keywords: scale, heterogeneity, biotic, invasion, hurricane, fire [ABSTRACT FROM AUTHOR]

Humid tropical forests play a dominant role in many global biogeochemical cycles, yet long-term records of tropical stream chemistry and its response to disturbance events such as severe storms and droughts are rare. Here we document the long-term variability in chemistry of two streams in the Luquillo Mountains, Puerto Rico over a period of 27 years. Our two focal study watersheds, the Río Icacos and Quebrada Sonadora, both drain several hundred hectares of tropical wet forests, and each received direct hits from Hurricanes Hugo (1989) and Georges (1998). They differ primarily in lithology (granitic vs. volcaniclastic) and elevation. Changes in major cations, anions, silica, and dissolved organic carbon were minimal over the study period, but the concentrations of nitrate show a strong response to hurricane disturbance and the longest time to recovery. Potassium also showed a large, although less consistent, response to disturbance. In the granitic terrain, nitrate concentrations exceeded long-term pre-hurricane background levels for over a decade, but were elevated in the volcaniclastic terrain for only 1–2 years. Lithology appears to be the primary driver explaining the different response trajectories of the two watersheds. In the granitic terrain, which showed slow recovery to pre-hurricane conditions, the quartz diorite bedrock weathers to produce coarser soils, deeper groundwater flow paths, and riparian zones with sharp spatial variation in redox conditions and very high nitrogen levels immediately adjacent to the stream. Groundwater flow paths are shallow and the levels of N in streamside groundwater are much lower in the volcaniclastic terrain. The recovery of vegetation following hurricane disturbance appears similar in the two watersheds, suggesting that the extent of structural damage to canopy trees determines the magnitude of NO 3 increases, but that the duration of elevated concentrations in stream water is a function of lithology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Examines how eight disturbances in climate change influence forest structure, composition, and function, and how climate change may influence the severity, frequency, and magnitude of disturbances to forests. Consideration of options for coping with disturbance under changing climate; Research needs to improve understanding of how climate change affects forest disturbances.

Discusses the impact of deliberate introductions of nonindigenous organisms on society. Reliance on non-native organisms; Effect of population growth and improved transcontinental transport; Increasing global threat against native biodiversity; Views; Where research is needed; Areas of agreement on species introductions. INSET: Research questions about introductions.

The Luquillo Experimental Forest (LEF) has a long history of research on tropical forestry, ecology, and conservation, dating as far back as the early 19th Century. Scientific surveys conducted by early explorers of Puerto Rico, followed by United States institutions contributed early understanding of biogeography, species endemism, and tropical soil characteristics. Research in the second half of the 1900s established the LEF as an exemplar of forest management and restoration research in the tropics. Research conducted as part of a radiation experiment funded by the Atomic Energy Commission in the 1960s on forest metabolism established the field of ecosystem ecology in the tropics. Subsequent research has built on these early advances to develop new theories on ecosystem response to disturbance regimes and the role of the biota in ecosystem resilience. Recent and current research in the LEF has advanced understanding of resilience to hurricane disturbances, human land use, gamma irradiation, landslides, drought, and warming, showing that even following the most severe disturbances (e.g., landslides, agriculture) forests reestablish within 60 years. Work in the LEF has reversed the paradigm that tropical ecosystems are fragile, but instead exhibit remarkable resilience to many forms of disturbance present at multiple spatial and temporal scales. Current research is already advancing understanding of how climate change and attendant effects on the disturbance regime might affect the composition, structure, and function of tropical forest ecosystems. • The Luquillo Experimental Forest (LEF) has a long history of research on tropical forestry, ecology, and conservation. • This research has advanced understanding of ecosystem resilience to many anthropogenic and non-anthropogenic disturbances. • The finding of resilience to disturbance challenged the paradigm that all tropical ecosystems are fragile in nature. • Current research reveals how ongoing climate change might alter the disturbance regime and responses of LEF ecosystems. [ABSTRACT FROM AUTHOR]

In this article the author discusses the need of conservationist to welcome non-native species base on its ecological impacts. He says that nativeness should not determine positive effects of species as such perception is not backed by data and non-native species benefits a region from increasing its number of species. He adds that eradication for non-natives are impractical as the ecosystem changes and the goal to restore it in rightful historical state is unattainable.