Jon Norberg

Response diversity, ecosystem change, and resilience

Biological diversity appears to enhance the resilience of desirable ecosystem states, which is required to secure the production of essential ecosystem services. The diversity of responses to environmental change among species contributing to the same ecosystem function, which we call response diversity, is critical to resilience. Response diversity is particularly important for ecosystem renewal and reorganization following change. Here we present examples of response diversity from both terrestrial and aquatic ecosystems and across temporal and spatial scales. Response diversity provides adaptive capacity in a world of complex systems, uncertainty, and human-dominated environments. We should pay special attention to response diversity when planning ecosystem management and restoration, since it may contribute considerably to the resilience of desired ecosystem states against disturbance, mismanagement, and degradation.

Phenotypic diversity and ecosystem functioning in changing environments: A theoretical framework

Biodiversity plays a vital role for ecosystem functioning in a changing environment. Yet theoretical approaches that incorporate diversity into classical ecosystem theory do not provide a general dynamic theory based on mechanistic principles. In this paper, we suggest that approaches developed for quantitative genetics can be extended to ecosystem functioning by modeling the means and variances of phenotypes within a group of species. We present a framework that suggests that phenotypic variance within functional groups is linearly related to their ability to respond to environmental changes. As a result, the long-term productivity for a group of species with high phenotypic variance may be higher than for the best single species, even though high phenotypic variance decreases productivity in the short term, because suboptimal species are present. In addition, we find that in the case of accelerating environmental change, species succession in a changing environment may become discontinuous. Our work suggests that this phenomenon is related to diversity as well as to the environmental disturbance regime, both of which are affected by anthropogenic activities. By introducing new techniques for modeling the aggregate behavior of groups of species, the present approach may provide a new avenue for ecosystem analysis.

Floating plant dominance as a stable state

Invasion by mats of free-floating plants is among the most important threats to the functioning and biodiversity of freshwater ecosystems ranging from temperate ponds and ditches to tropical lakes. Dark, anoxic conditions under thick floating-plant cover leave little opportunity for animal or plant life, and they can have large negative impacts on fisheries and navigation in tropical lakes. Here, we demonstrate that floating-plant dominance can be a self-stabilizing ecosystem state, which may explain its notorious persistence in many situations. Our results, based on experiments, field data, and models, represent evidence for alternative domains of attraction in ecosystems. An implication of our findings is that nutrient enrichment reduces the resilience of freshwater systems against a shift to floating-plant dominance. On the other hand, our results also suggest that a single drastic harvest of floating plants can induce a permanent shift to an alternative state dominated by rooted, submerged growth forms.

The evolutionary ecology of metacommunities.

Research on the interactions between evolutionary and ecological dynamics has largely focused on local spatial scales and on relatively simple ecological communities. However, recent work demonstrates that dispersal can drastically alter the interplay between ecological and evolutionary dynamics, often in unexpected ways. We argue that a dispersal-centered synthesis of metacommunity ecology and evolution is necessary to make further progress in this important area of research. We demonstrate that such an approach generates several novel outcomes and substantially enhances understanding of both ecological and evolutionary phenomena in three core research areas at the interface of ecology and evolution.

A Network Approach for Analyzing Spatially Structured Populations in Fragmented Landscape

We extend the recently proposed graph-theoretical landscape perspective by applying some network-centric methods mainly developed in the social sciences. The methods we propose are suitable to (1) identify individual habitat patches that are disproportionally high in importance in preserving the ability of organisms to traverse the fragmented landscape, and (2) find internally well-connected compartments of habitat patches that contribute to a spatial compartmentalization of species populations. We demonstrate the utility of these methods using an agricultural landscape with scattered dry-forest patches in southern Madagascar, inhabited by the ring-tailed lemur, Lemur catta. We suggest that these methods are particularly suitable in landscapes where species’ traversability is not fully inhibited by fragmentation, but merely limited. These methods are potentially highly relevant in studying spatial aspects of resilience and in the design of natural reserves.

Social-ecological systems as complex adaptive systems : modeling and policy implications

Systems linking people and nature, known as social-ecological systems, are increasingly understood as complex adaptive systems. Essential features of these complex adaptive systems – such as nonlinear feedbacks, strategic interactions, individual and spatial heterogeneity, and varying time scales – pose substantial challenges for modeling. However, ignoring these characteristics can distort our picture of how these systems work, causing policies to be less effective or even counterproductive. In this paper we present recent developments in modeling social-ecological systems, illustrate some of these challenges with examples related to coral reefs and grasslands, and identify the implications for economic and policy analysis.

Adaptive Management of the Great Barrier Reef and the Grand Canyon World Heritage Areas

Abstract Conventional perceptions of the interactions between people and their environment are rapidly transforming. Old paradigms that view humans as separate from nature, natural resources as inexhaustible or endlessly substitutable, and the world as stable, predictable, and in balance are no longer tenable. New conceptual frameworks are rapidly emerging based on an adaptive approach that focuses on learning and flexible management in a dynamic social-ecological landscape. Using two iconic World Heritage Areas as case studies (the Great Barrier Reef and the Grand Canyon) we outline how an improved integration of the scientific and social aspects of natural resource management can guide the evolution of multiscale systems of governance that confront and cope with uncertainty, risk, and change in an increasingly human-dominated world.

Linking Nature's services to ecosystems: some general ecological concepts

Abstract I present a selected review of ecological concepts that are important for understanding how nature’s services are linked to their support system, the ecosystem. The paper is mainly aimed at an audience of non-biologists to facilitate cooperation among disciplines. A list of services compiled from the literature is classified according to ecological criteria that relate to the properties of the services. These criteria are: (1) if the goods or services are produced and maintained within the ecosystem or shared with other ecosystems; (2) if the goods or object of the service are living or inorganic material; and (3) what biological unit is associated with production and maintenance, i.e. an individual, a species, a group of species, an entire community, the ecosystem, the landscape or on a global scale. Using these criteria I have identified and selected three major groups of ecosystem services for which some common ecological concepts apply. These are: (1) the maintenance of populations; (2) the use of ecosystems as filters of externally imposed compounds; and (3) the property of biological units to create organization through selective processes. These three categories are examined and exemplified in detail.

Modelling output and retention of suspended solids in an integrated salmon–mussel culture

The most marked effect of cage aquaculture in an environment is the output of suspended solids and dissolved nutrients, which in some cases have been shown to cause environmental degradation. Instead of using traditional methods built on technological solutions, integrated farming methods have been put forward as a mean for treating nutrients and particulate wastes from fish cage farming. However, the results from integrated experiments, where filter feeders have been used to absorb suspended particles from fish cages, have not in many cases resulted in the expected beneficial effects. By modelling the output of waste from a salmon cage cultivation and particle filtration by mussels, the following main constraints for using filter feeders for removing particles from fish cages were identified: (1) Suspended solids from the fish cages will be highly diluted by the large volume of water passing through the cages. During continuous feeding (demand feeding) the concentration of released suspended solids was low (0.06‐0.3 mg l 1 ). Only when fish density in the cages was high prior to harvest, and water currents were slow (0.03‐0.05 m s 1 ), the increase in released concentrations were \0.1 mg l 1 . (2) Addition of feed in pulses showed a 3‐30-fold increase in water particle concentration, but the short duration of a pulse and saturation of mussel feeding would make long term seston concentration more important for mussel growth. (3) The potential particle retention from a rich pulse was limited by mussel pseudofaeces threshold level. It is concluded that, in a co-cultivation of mussels and salmons, the ambient seston concentration is of greater importance in controlling mussel growth, and increases in suspended solids from the fish cages may contribute significantly only during periods of low plankton production.

Mapping bundles of ecosystem services reveals distinct types of multifunctionality within a Swedish landscape.

Ecosystem services (ES) is a valuable concept to be used in the planning and management of social–ecological landscapes. However, the understanding of the determinant factors affecting the interaction between services in the form of synergies or trade-offs is still limited. We assessed the production of 16 ES across 62 municipalities in the Norrström drainage basin in Sweden. We combined GIS data with publically available information for quantifying and mapping the distribution of services. Additionally, we calculated the diversity of ES for each municipality and used correlations and k-means clustering analyses to assess the existence of ES bundles. We found five distinct types of bundles of ES spatially agglomerated in the landscape that could be explained by regional social and ecological gradients. Human-dominated landscapes were highly multifunctional in our study area and urban densely populated areas were hotspots of cultural services.