How accurate are population models? Lessons from landscape‐scale tests in a fragmented system

Disturbance to a foraging seabird by sea-based tourism: Implications for reserve management in marine protected areas

Coastal zones, and in particular offshore areas, are coming under ever-increasing pressure from human development. Therefore, the evaluation of habitat quality is of vital importance for management of coastal zones. The InVEST model adopts a multi-module and multi-level design form, which has the advantages of strong visualization and fast calculation. As a result, this study used the InVEST-Habitat quality (HQ) model to assess the habitat quality of the Tongzhou Bay offshore area. Development activities were included in the classification of habitat types and the benthic habitat suitability index was used to describe the spatial variation in habitat quality of the offshore area. The results showed that the methodological approach mentioned above achieved a more detailed assessment of the spatial variation in habitat quality. The empirical model constructed based on the relationship between the Shannon–Weiner index and environmental factors performed well in revealing the suitability of habitat, with the regression equation showing an R2 of 0.57 and R2 of 0.5 significant at level of p < 0.05. The habitat suitability of Tongzhou Bay water was mainly influenced by aquaculture and industrial sea use. The habitat quality of Tongzhou Bay was relatively low due to disturbance by coastal development and a low water habitat suitability. The distribution of habitat quality in Tongzhou Bay was uneven and improved with the increase of the distance from the coast. Improvement of the habitat quality of Tongzhou Bay requires strict control of sea reclamation, optimization of the structure of offshore aquaculture, improvements to water quality and habitat suitability, and strengthening of the protection of areas of high habitat quality. This study provides a novel method for evaluating habitat quality of offshore areas.

We examine the evolutionary stability of year‐round residency in territorial populations, where breeding sites are a limiting resource. The model links individual life histories to the population‐wide competition for territories and includes spatial variation in habitat quality as well as a potential parent‐offspring conflict over territory ownership. The general form of the model makes it applicable to the evolution of dispersal, migration, partial migration, and delayed dispersal (offspring retention). We show that migration can be evolutionarily stable only if year‐round residency in a given area would produce a sink population, where mortality exceeds reproduction. If this applies to a fraction of the breeding habitat only, partial migration is expected to evolve. In the context of delayed dispersal, habitat saturation has been argued to form an ecological constraint on independent breeding, which favors offspring retention and cooperative breeding. We show that habitat saturation must be considered as a dynamic outcome of birth, death, and dispersal rates in the population, rather than an externally determined constraint. Although delayed dispersal often associates with intense competition for territories, life‐history traits have direct effects on stable dispersal strategies, which can often override the effect of habitat saturation. As an example, high survival of floaters selects against delayed dispersal, even though it increases the number of competitors for each breeding vacancy (the “habitat saturation factor”). High survival of territory owners, by contrast, generally favors natal philopatry. We also conclude that spatial variation in habitat quality only rarely selects for delayed dispersal. Within a population, however, offspring retention is more likely in high‐quality territories.

We examine the evolutionary stability of year-round residency in territorial populations, where breeding sites are a limiting resource. The model links individual life histories to the population-wide competition for territories and includes spatial variation in habitat quality as well as a potential parent-offspring conflict over territory ownership. The general form of the model makes it applicable to the evolution of dispersal, migration, partial migration, and delayed dispersal (offspring retention). We show that migration can be evolutionarily stable only if year-round residency in a given area would produce a sink population, where mortality exceeds reproduction. If this applies to a fraction of the breeding habitat only, partial migration is expected to evolve. In the context of delayed dispersal, habitat saturation has been argued to form an ecological constraint on independent breeding, which favors offspring retention and cooperative breeding. We show that habitat saturation must be considered as a dynamic outcome of birth, death, and dispersal rates in the population, rather than an externally determined constraint. Although delayed dispersal often associates with intense competition for territories, life-history traits have direct effects on stable dispersal strategies, which can often override the effect of habitat saturation. As an example, high survival of floaters selects against delayed dispersal, even though it increases the number of competitors for each breeding vacancy (the "habitat saturation factor"). High survival of territory owners, by contrast, generally favors natal philopatry. We also conclude that spatial variation in habitat quality only rarely selects for delayed dispersal. Within a population, however, offspring retention is more likely in high-quality territories.

Very high resolution Earth Observation features for testing the direct and indirect effects of landscape structure on local habitat quality

Many bacterial species carry plasmids that encode both the production of a highly specific toxin (bacteriocin) that kills competitors of the same species and immunity to that toxin. A great diversity of bacteriocins is produced within a single species. I present a model for the dynamics of competition between allelopathic and susceptible types. The model applies to most kinds of allelopathic competition. My primary goal is, however, to explain the widespread genetic polymorphism for bacteriocins. The model includes competition for scarce resources, competition through toxin production, spatial diffusion of individuals and toxins at varying rates and spatial variation in habitat quality. I draw three main conclusions from this ‘reaction—diffusion’ model. (1) Polymorphism of toxin producers and susceptibles cannot be maintained within a single spatial location when individuals and the toxin mix randomly. (2) Susceptibles are generally favoured in poor habitats, where the rate of resource competition per interaction increases relative to the resource-independent rate of toxic killing. By contrast, toxic producers are generally favoured in good habitats, where the rate of resource competition is lower. (3) Spatial variation in habitat quality can lead to spatial polymorphism; susceptibles tend to win in poor habitats and producers tend to win in good habitats.

What drives long‐distance dispersal? A test of theoretical predictions

Variation in habitat quality affects individual fitness through the accumulation of benefits and costs over time. Although an individual's fitness and susceptibility to mortality are consequences of these past experiences, current analytical models do not quantify the cumulative effects of resources, risks, and environmental conditions on survival. We developed the Survival and Habitat Quality model (SHQ), which redefines survival as a cumulative process and measures habitat quality by its aggregate effect on survival through time. SHQ is an autoregressive time‐series model that uses fine‐scale tracking data, remotely sensed environmental data, and computational power to quantify the cumulative effects of spatial variation in habitat quality on survival without relying on subjective, user‐defined lag effects. We tested SHQ on simulated data and on pronghorn data in South Dakota, USA. Compared to a traditional survival model, SHQ was more precise and accurate at estimating cumulative effects of habitat on survival. Using model output, we were also able to generate maps predicting areas of high and low pronghorn survival. SHQ is a conceptual and methodological advance that explicitly integrates individuals' day‐to‐day interactions with their surroundings to identify ultimate sources of mortality. The model is a novel and accurate tool for assessing habitat quality and identifying management actions that increase individual survival and population growth. More broadly, SHQ's flexible mathematical framework captures the full spatial and temporal scope of processes affecting survival, providing a powerful means for understanding the environmental basis of fitness.

Understanding spatiotemporal variation in habitat quality is essential for guiding wildlife reintroduction and restoration programs. The habitat productivity hypothesis posits that home range size is inversely related to habitat quality. Thus, home range size may be used as a proxy for habitat quality and can identify important land cover features for a recovering species. We sought to quantify variation in home range size across the biological cycle (seasons) for a reintroduced elk (Cervus canadensis) population in southwestern Virginia, USA and quantify habitat quality by linking home range sizes to the land cover types they contain using linear mixed-effects models. We found mean home range size was largest during late gestation for female elk. Additionally, throughout the year, smaller home ranges were associated with larger proportions of non-forested habitats whereas forested habitats were generally the opposite. However, both presumed poor- and high-quality habitats influenced female elk space use. Our approach revealed spatial variation in habitat quality for a recovering elk herd, demonstrated the importance of non-forested habitats to elk, can guide decisions regarding the location of future elk reintroduction programs, and serve as a model for evaluating habitat quality associated with wildlife reintroductions.

Age class interactions in a marine goby, Elacatinus prochilos (Böhlke and Robins, 1968)

We examined the spatial distribution of water vole populations in four consecutive years and investigated whether the regional population processes of extinction, recolonisation and migration influence distribution and persistence. We examined how such regional processes are influenced by spatial variation in habitat quality. In addition, we assessed the relevance of metapopulation concepts for understanding the dynamics of species that deviate from classical metapopulation assumptions and developing conservation measures for them. Populations were patchy and discrete, and the patchy distribution was not static between years. Population turnover occurred even in the absence of predatory mink, which only influenced the network of populations at the end of the study. Most populations were clustered close together in the upper tributaries. Local population persistence was predominantly influenced by population size: large populations were more persistent. Recolonisation rates were influenced by isolation and habitat quality. The isolation estimates which best explained the distribution of water vole populations incorporated straight‐line distances, suggesting water voles disperse overland. The distribution of recolonised sites indicated that dispersing voles actively selected habitat on the basis of its quality. Water voles depart from some of the assumptions made by frequently used metapopulation models. In particular there is no clear binary distinction between suitable and non‐suitable habitat. Accounting for variation in habitat quality before investigating temporal changes in population distribution allowed us to demonstrate that the key metapopulation processes were important. The significance of regional population processes relative to local population processes may have increased in declining, fragmented populations compared to pristine regional populations. We hypothesise that although mink predation is likely to eventually cause regional extinction in many areas, metapopulation processes have delayed this decline. Consequently, conservation measures should take into account mink predation rates and regional population processes, before considering aspects of habitat quality.

Variation in habitat quality is common across terrestrial, freshwater, and marine habitats. We investigated how habitat quality influenced the reproductive potential of mud crabs across 30 oyster reefs that were degraded to different extents. We further coupled this field survey with a laboratory experiment designed to mechanistically determine the relationship between resource consumption and reproductive performance. We show a >10-fold difference in average reproductive potential for crabs across reefs of different quality. Calculated consumption rates for crabs in each reef, based on a type II functional response, suggest that differences in reproductive performance may be attributed to resource limitation in poor quality reefs. This conclusion is supported by results of our laboratory experiment where crabs fed a higher quality diet of abundant animal tissue had greater reproductive performance. Our results demonstrate that spatial variation in habitat quality can be a considerable contributor to within-population individual variation in reproductive success (i.e., demographic heterogeneity). This finding has important implications for assessing population extinction risk.

Dispersal theory generally predicts kin competition, inbreeding, and temporal variation in habitat quality should select for dispersal, whereas spatial variation in habitat quality should select against dispersal. The effect of predation on the evolution of dispersal is currently not well-known: because predation can be variable in both space and time, it is not clear whether or when predation will promote dispersal within prey. Moreover, the evolution of prey dispersal affects strongly the encounter rate of predator and prey individuals, which greatly determines the ecological dynamics, and in turn changes the selection pressures for prey dispersal, in an eco-evolutionary feedback loop. When taken all together the effect of predation on prey dispersal is rather difficult to predict. We analyze a spatially explicit, individual-based predator-prey model and its mathematical approximation to investigate the evolution of prey dispersal. Competition and predation depend on local, rather than landscape-scale densities, and the spatial pattern of predation corresponds well to that of predators using restricted home ranges (e.g. central-place foragers). Analyses show the balance between the level of competition and predation pressure an individual is expected to experience determines whether prey should disperse or stay close to their parents and siblings, and more predation selects for less prey dispersal. Predators with smaller home ranges also select for less prey dispersal; more prey dispersal is favoured if predators have large home ranges, are very mobile, and/or are evenly distributed across the landscape.

Despite Guangxi’s unique ecological diversity and its important role in land-based ecological security and conservation, research on the assessment and prediction of its habitat quality under the influences of rapid urbanization and environmental pressures remains limited. This study systematically analyzes the spatial and temporal dynamics of land use and habitat quality in Guangxi from 2000 to 2020 using the PLUS-InVEST model and simulates future scenarios for 2030. These scenarios include the Natural Development (ND) scenario, Urban Development (UD) scenario, and Cropland and Ecological Protection (CE) scenario. The results indicate the following: (1) Over the past two decades, rapid urban and construction land expansions in Guangxi intensified their negative impact on habitat degradation. Additionally, the disproportionate change between rural settlement land and rural population warrants attention. (2) Although ecological restoration measures have played a positive role in mitigating habitat degradation, their effects have been insufficient to counterbalance the negative impacts of construction land expansion, highlighting the need for balanced land use planning and urbanization policies. (3) The expansion of rural residential areas had a greater impact on regional habitat quality degradation than urban and infrastructure expansion. Moderate urbanization may contribute to habitat quality improvement. (4) The CE scenario shows the most significant improvement in habitat quality (an increase of 0.13%), followed by the UD scenario, which alleviates habitat degradation by reducing pressure on rural land. In contrast, the ND scenario predicts further declines in habitat quality. Furthermore, land use planning, restoration measures, and sustainable development policies are key factors influencing habitat quality changes. These findings emphasize the importance of integrating land use strategies with ecological restoration measures to balance economic growth and biodiversity conservation, especially in rapidly urbanizing regions.

Monitoring spatio-temporal dynamics of habitat quality in Nansihu Lake basin, eastern China, from 1980 to 2015