Population dynamics under increasing environmental variability: implications of climate change for ecological network design criteria

There is growing evidence that climate change causes an increase in variation in conditions for plant and animal populations. This increase in variation, e.g. amplified inter-annual variability in temperature and rainfall has population dynamical consequences because it raises the variation in vital demographic rates (survival, reproduction) in these populations. In turn, this amplified environmental variability enlarges population extinction risk. This paper demonstrates that currently used nature conservation policies, principles, and generic and specific design criteria have to be adapted to these new insights. A simulation shows that an increase in variation in vital demographic rates can be compensated for by increasing patch size. A small, short-lived bird species like a warbler that is highly sensitive to environmental fluctuations needs more area for compensation than a large, long-lived bird species like a Bittern. We explore the conservation problems that would arise if patches or reserve sizes would need to be increased, e.g. doubled, in order to compensate for increase in environmental variability. This issue has serious consequences for nature policy when targets are not met, and asks for new design criteria.     

Assessing the effects of applying landscape ecological spatial concepts on future habitat quantity and quality in an urbanizing landscape

This study develops a quantitative approach to evaluate the application of design concepts that link landscape ecology theory to landscape planning. Landscape ecology principles were used to develop spatial concepts for creating an armature of open space in areas subject to rapid urbanization. It focuses on the predicted urban expansion of Damascus, Oregon, as a case study. An alternative futures study was used to test three open space spatial concepts for patches, corridors and networks contrasted with compact and dispersed urban development patterns. Eight scenarios of land use and land cover, over 50 years, were defined based on different spatial design concepts to evaluate their effects on habitat quantity and quality and analyze the tradeoffs between urban development and conservation of three focal wildlife species: red-legged frog, western meadowlark, and Douglas squirrel. Open space spatial concepts highly influenced habitat quantity and quality differences among scenarios. Development patterns showed lower influence on those variables. Scenarios with no landscape ecological spatial concept provided the most land for urban development but reduced habitat quantity and quality. Greenway scenarios presented increases of habitats, but failed to provide sufficient habitats for western meadowlark. Park system scenarios also presented an increase on the amount of habitats, but high-quality habitats for western meadowlark and red-legged frog decreased. Network scenarios presented the best overall amount of habitats and increase of high-quality habitats for the three species, but constrained urban development options.     

The past and future of modeling forest dynamics: from growth and yield curves to forest landscape models

Context

Quantitative models of forest dynamics have followed a progression toward methods with increased detail, complexity, and spatial extent.

Objectives

We highlight milestones in the development of forest dynamics models and identify future research and application opportunities.

Methods

We reviewed milestones in the evolution of forest dynamics models from the 1930s to the present with emphasis on forest growth and yield models and forest landscape models We combined past trends with emerging issues to identify future needs.

Results

Historically, capacity to model forest dynamics at tree, stand, and landscape scales was constrained by available data for model calibration and validation; computing capacity; model applicability to real-world problems; and ability to integrate biological, social, and economic drivers of change. As computing and data resources improved, a new class of spatially explicit forest landscape models emerged.

Conclusions

We are at a point of great opportunity in development and application of forest dynamics models. Past limitations in computing capacity and in data suitable for model calibration or evaluation are becoming less restrictive. Forest landscape models, in particular, are ready to transition to a central role supporting forest management, planning, and policy decisions.

Recommendations

Transitioning forest landscape models to a central role in applied decision making will require greater attention to evaluating performance; building application support staffs; expanding the included drivers of change, and incorporating metrics for social and economic inputs and outputs.

     

Coupled dynamics of urban landscape pattern and socioeconomic drivers in Shenzhen,China

The effects of land use policy and socioeconomic changes on urban landscape dynamics have been increasingly investigated around the world, but our knowledge of the underlying processes of these effects is still inadequate for sustainably managing urban ecosystems. Thus, the main goal of this study was to understand: (1) the changes in urban landscape, population, and economic conditions over a 36-year period, and (2) the coupled dynamics of land use policy, landscape structure, major demographic features, and three kinds of industries in one of the most dazzling modern cities of China—the Shenzhen special economic zone (SEZ). The landscape expansion index was used to explore the developed-land expansion under different land use policies while structural equation modeling (SEM) was used to analyze the relationship among three variables (Land Cover Change or LCC, Economy, and Population). We found that the urban expansion during the four periods (1973–1979, 1979–1995, 1995–2003, and 2003–2009) was not always at the expense of urban vegetation cover. The importance of each socioeconomic driver during the four periods was not consistent over time, with policy shifts as the primary driver. Our SEM showed that Economy played a more important role than Population in driving LCC in the Shenzhen SEZ. Meanwhile, the secondary and tertiary industries had a stronger influence than the primary industry; and the floating population had a greater effect than the registered permanent population.     

Multiscale sources of variation in ecological variables: modeling spatial dispersion,elaborating sampling designs

Detection of structured spatial variation and identification of spatial scales are important aspects of ecological studies. Spatial structures can correspond to physical features of the environment or to intrinsic characteristics of ecological processes and phenomena. Spatial variability has been approached through several techniques such as classical analysis of variance, or the calculation of fractal dimensions, correlograms or variograms. Under certain assumptions, these techniques are all closely related to one another and represent equivalent tools to characterize spatial structures.Our perception of ecological variables and processes depends on the scale at which variables are measured. We propose simple nested sampling designs enabling the detection of a wide range of spatial structures that show the relationships among nested spatial scales. When it is known that the phenomenon under study is structured as a nested series of spatial scales, this provides useful information to estimate suitable sampling intervals, which are essential to establish the relationships between spatial patterns and ecological phenomena. The use of nested sampling designs helps in choosing the most suitable solutions to reduce the amount of random variation resulting from a survey. These designs are obtained by increasing the sampling intensity to detect a wider spectrum of frequencies, or by revisiting the sampling technique to select more representative sampling units.     

Quantifying the speed, growth modes, and landscape pattern changes of urbanization: a hierarchical patch dynamics approach

Urbanization transforms landscape structure and profoundly affects biodiversity and ecological processes. To understand and solve these ecological problems, at least three aspects of spatiotemporal patterns of urbanization need to be quantified: the speed, urban growth modes, and resultant changes in landscape pattern. In this study, we quantified these spatiotemporal patterns of urbanization in the central Yangtze River Delta region, China from 1979 to 2008, based on a hierarchical patch dynamics framework that guided the research design and the analysis with landscape metrics. Our results show that the urbanized area in the study region increased exponentially during the 30 years at the county, prefectural, and regional levels, with increasing speed down the urban hierarchy. Three growth modes—infilling, edge-expanding, and leapfrogging—operated concurrently and their relative dominance shifted over time. As urbanization progressed, patch density and edge density generally increased, and the connectivity of urban patches in terms of the average nearest neighbor distance also increased. While landscape-level structural complexity also tended to increase, the shape of individual patches became increasingly regular. Our results suggest that whether urban landscapes are becoming more homogenous or heterogeneous may be dependent on scale in time and space as well as landscape metrics used. The speed, growth modes, and landscape pattern are related to each other in complicated fashions. This complex relationship can be better understood by conceptualizing urbanization not simply as a dichotomous diffusion-coalescence switching process, but as a spiraling process of shifting dominance among multiple growth modes: the wax and wane of infilling, edge-expansion, and leapfrog across the landscape.     

A spatial analysis of land cover patterns and its implications for urban avifauna persistence under climate change

Context

Although biodiversity in cities is essential to ensure the healthy functioning of ecosystems and biosecurity over time, biodiversity loss resulting from human interventions in land cover patterns is widespread in urban landscapes. In the Southern Hemisphere, climate change is likely to accelerate the process of landscape upheavals, and consequently biodiversity loss.

Objectives & Methods

The aim of this research is to test the potentials of landscape pattern composition and configuration in safeguarding indigenous avifauna against the local impacts of climate change in urban landscapes, with reference to New Zealand. To build up a platform for landscape pattern interpretation, the literature was reviewed and semi-structured interviews with six subject-matter experts were conducted to provide information about the most important avifauna in the study area, key information on their ecological traits and niches, possible impacts of climate change on their primary habitats, and spatial requirements for ongoing species survival as the climate continues to change. A spatial analysis of land cover patterns was undertaken in Wellington, New Zealand using GIS and FRAGSTATS.

Results

Although there are still opportunities for biodiversity conservation in the study area, the current land cover patterns are unlikely to safeguard the selected species against climate change impacts.

Conclusions

Eight implications for avifauna persistence under climate change are discussed for the first time in relation to a New Zealand context. These implications can give rise to a higher level of informed decision-making on a wide range of practices for biodiversity conservation related to uncertainties associated with climate change.

     

Response of vegetation and fire to Little Ice Age climate change: regional continuity and landscape heterogeneity

Late-Holocene climatic conditions in the upper Great Lakes region have changed sufficiently to produce significant changes in vegetation and fire regimes. The objective of this study was to determine how the vegetation mosaic and fire regimes on an oak (Quercus spp.)- and pine (Pinus spp.)-dominated sand plain in northwestern Wisconsin responded to climatic changes of the past 1,200 years. We used pollen and charcoal records from a network of sites to investigate the range of natural variability of vegetation on a 1,500-km² landscape on the southern part of the sand plain. A major vegetation shift from jack pine (Pinus banksiana) and red pine (P. resinosa) to increased abundance of white pine (P. strobus) occurred between 700 and 600 calendar years before present (cal yr BP), apparently corresponding to more mesic conditions regionally. A decrease in charcoal accumulation rate also occurred at most sites but was not synchronous with the vegetation change. At some sites there were further changes in vegetation and fire regimes occurring ～500–300 cal yr BP, but these changes were not as strong or unidirectional as those that occurred 700–600 cal yr BP. Our results suggest that both the composition and the distribution of vegetation of the southern part of the sand plain have been sensitive to relatively small climatic changes, and that the vegetation at the time of European settlement was a transitory phenomenon, rather than a long-term stable condition.     

Accessibility as a determinant of landscape transformation in western Honduras: linking pattern and process

This study evaluates the relationship between landscape accessibility and land cover change in Western Honduras, and demonstrates how these relationships are influenced by social and economic processes of land use change in the region. The study area presents a complex mosaic of land cover change processes that involve approximately equal amounts of reforestation and deforestation. Landsat Thematic Mapper (TM) satellite imagery of 1987, 1991 and 1996 was used to create three single date classifications and a land cover change image depicting the sequence of changes in land cover between 1987–1991–1996. An accessibility analysis examined land cover change and landscape fragmentation relative to elevation and distance from roads. Between 1987 and 1991, results follow ‘expected’ trends, with more accessible areas experiencing greater deforestation and fragmentation. Between 1991 and 1996 this trend reverses. Increased deforestation is found in areas distant from roads, and at higher elevations; a result of government policies promoting expansion of mountain coffee production for export. A ban on logging, and abandonment of marginally productive agricultural fields due to agricultural intensification in other parts of the landscape, has led to increased regrowth in accessible regions of the landscape. Roads and elevation also present different obstacles in terms of their accessibility, with the smallest patches of cyclical clearing and regrowth, relating mostly to the agricultural fallow cycle, found at the highest elevations but located close to roads. This research highlights the need to locate analyses of land cover change within the context of local socio-economic policies and land use processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Occurrence pattern of Pararge aegeria (Lepidoptera: Nymphalidae) with respect to local habitat suitability, climate and landscape structure

Distribution patterns of wild species are affected by environmental variables, such as climate, anthropogenic land use or habitat quality, which act simultaneously at different scales. To examine the relative importance of particular factors and scales on population response we investigated the speckled wood butterfly Pararge aegeria (L.) as a model organism occupying semi-natural habitats. Its distribution was recorded in 23 study sites (5×5 km) over a 2 year study period. The sites were located in agricultural landscapes within seven Temperate European countries. Environmental predictors were mapped at a local and a regional scale. Logistic regression models were then developed to represent humid (beneficial) and dry (adverse) weather conditions during larval development. The humid year model predicted that P. aegeria is equally but generally not very dependent on local and regional factors, resulting in generally high occurrence probabilities. In contrast, the dry year model predicted severe restrictions of P. aegeria to both high quality patches and landscapes with beneficial structural and climatic preconditions. As both models resulted in entirely different predictions, our study showed that the sensitivity of P. aegeria to local and landscape features might change, and that factors of less importance could easily become limiting factors. The results stress that high quality landscape is important at both the local and regional scale even for species that are considered relatively robust. They also sound a note of caution when predictions about population response for management purposes are based on just a single or a few year(s) of observation.     

The impact of shifting cultivation on a rainforest landscape in West Kalimantan: spatial and temporal dynamics

To assess the role of shifting cultivation in the loss of rainforests in Indonesia, we examined the spatial and temporal dynamics of traditional land-use north of Gunung Palung National Park in West Kalimantan. We analyzed the abundance, size, frequency, and stature (by tree size) of discrete management units (patches) as a function of land-use category and distance from the village. Data were gathered from point samples along six 1.5-km transects through the landscape surrounding the Dayak village of Kembera. Most land was managed for rice, with 5% in current production, 12% in wet-rice fallows (regenerating swamp forest), and 62% in dry-rice fallows (regenerating upland forest). The proportion of land in dry-rice increased with distance from the village; rubber gardens (17% of the total area), dominated close to the village. The size of rubber trees declined with distance, reflecting the recent establishment of rubber gardens far from the village. Fruit gardens accounted for only 4% of the area. From interviews in Kembera and three other villages, we estimated rates of primary forest clearing and documented changes in land-use. Most rice fields were cleared from secondary forest fallows. However, 17% of dry-rice fields and 9% of wet-rice fields were cleared from primary forest in 1990, resulting in the loss of approximately 12 ha of primary forest per village. Almost all dry-rice fields cleared from primary forest were immediately converted to rubber gardens, as were 39% of all dry-rice fields cleared from fallows. The rate of primary forest conversion increased dramatically from 1990 to 1995, due not to soil degradation or population growth but rather to changes in the socio-economic and political environment faced by shifting cultivators. Although the loss of primary forest is appreciable under shifting cultivation, the impact is less than that of the major alternative land-uses in the region: timber extraction and oil palm plantations.     

The social and spatial dynamics of community food production: a landscape approach to policy and program development

Community food production in the form of home gardening, community gardening, school gardening, and urban farming continues to increase in popularity in many parts of the world. This interest has led to public and private investment in community food production and increased need for urban agricultural planning as a way to manage growth and prioritize resource allocation. Municipal planning and thoughtful institutional support for the practice will require program evaluation and greater attention to the spatial composition and configuration of this widely dispersed practice. This article explores the results of community-supported landscape socio-ecological research in Madison, WI (USA) to assess the spatial and social dynamics of community food production. Results indicate that community food production resources are unevenly distributed across the study area. Historic community garden placement does appear to be consistent with community prioritization which dictates placing resources in areas with low median household income. However, home garden presence and recent community garden placement both occur in areas of higher than average median household income. Specific focus is placed on how an understanding of landscape placement and pattern has helped inform attempts to meet municipal and regional objectives in addressing urban food insecurity.     

Occupancy pattern of a long-horned beetle in a variegated forest landscape: linkages between tree quality and forest cover across spatial scales

Context

Interactions between landscape-scale processes and fine-grained habitat heterogeneity are usually invoked to explain species occupancy in fragmented landscapes. In variegated landscapes, however, organisms face continuous variation in micro-habitat features, which makes necessary to consider ecologically meaningful estimates of habitat quality at different spatial scales.

Objectives

We evaluated the spatial scales at which forest cover and tree quality make the greatest contribution to the occupancy of the long-horned beetle Microplophorus magellanicus (Coleoptera: Cerambycidae) in a variegated forest landscape.

Methods

We used averaged data of tree quality (as derived from remote sensing estimates of the decay stage of single trees) and spatially independent pheromone-baited traps to model the occurrence probability as a function of multiple cross-scale combinations between forest cover and tree quality (with scales ranging between 50 and 400 m).

Results

Model support and performance increased monotonically with the increasing scale at which tree quality was measured. Forest cover was not significant, and did not exhibit scale-specific effects on the occurrence probability of M. magellanicus. The interactive effect between tree quality and forest cover was stronger than the independent (additive) effects of tree quality and particularly forest cover. Significant interactions included tree quality measured at spatial scales ≥200 m, but cross-scale interactions occurred only in four of the seven best-supported models.

Conclusions

M. magellanicus respond to the high-quality trees available in the landscape rather than to the amount of forest per se. Conservation of viable metapopulations of M. magellanicus should consider the quality of trees at spatial scales >200 m.

     

Impacts of changing climate and land use on vegetation dynamics in a Mediterranean ecosystem: insights from paleoecology and dynamic modeling

Forests near the Mediterranean coast have been shaped by millennia of human disturbance. Consequently, ecological studies relying on modern observations or historical records may have difficulty assessing natural vegetation dynamics under current and future climate. We combined a sedimentary pollen record from Lago di Massacciucoli, Tuscany, Italy with simulations from the LandClim dynamic vegetation model to determine what vegetation preceded intense human disturbance, how past changes in vegetation relate to fire and browsing, and the potential of an extinct vegetation type under present climate. We simulated vegetation dynamics near Lago di Massaciucoli for the last 7,000 years using a local chironomid-inferred temperature reconstruction with combinations of three fire regimes (small infrequent, large infrequent, small frequent) and three browsing intensities (no browsing, light browsing, and moderate browsing), and compared model output to pollen data. Simulations with low disturbance support pollen-inferred evidence for a mixed forest dominated by Quercus ilex (a Mediterranean species) and Abies alba (a montane species). Whereas pollen data record the collapse of A. alba after 6000 cal yr bp, simulated populations expanded with declining summer temperatures during the late Holocene. Simulations with increased fire and browsing are consistent with evidence for expansion by deciduous species after A. alba collapsed. According to our combined paleo-environmental and modeling evidence, mixed Q. ilex and A. alba forests remain possible with current climate and limited disturbance, and provide a viable management objective for ecosystems near the Mediterranean coast and in regions that are expected to experience a mediterranean-type climate in the future.     

Cultural landscapes of the future: using agent-based modeling to discuss and develop the use and management of the cultural landscape of South West Devon

Context

Hedgerows are typical landscape features of high environmental and cultural value that often have been sacrificed for agricultural intensification and scale enlargement.

Objectives

We studied the dynamics of hedgerow quality over time in a case study area renowned for its hedgerow landscapes: South West Devon (UK) answering the following research questions: (1) how does the imperative of scale enlargement affect hedgerow quality? and (2) to what extent can cultural landscape degradation be countered by targeted policies?

Methods

We applied an agent-based modeling approach, parameterized with a site specific survey, to explore and discuss outcomes of future landscape change with stakeholders and co-designed preferred scenarios of landscape change during a workshop.

Results

Outcomes suggested that in the case-study area, scale enlargement has a negative effect on hedgerow quality when agri-environment scheme subsidies (AES) are low. In contrast, if the level of AES enrollment is high, scale enlargement can have a positive effect on hedgerow quality, as large holders are more likely to enroll for AES. Stakeholders acknowledged the need for agricultural intensification, but at the same time valued biodiversity and environmental value of the landscape in South West Devon.

Conclusion

Current AES are able to retain a decent hedgerow quality. With lower AES, scale enlargement can have an invigorative effect on hedgerow quality as land managers of larger farms will be less likely to join AES As an addition to AES, harvesting wood fuel from coppiced hedgerows appears a promising way to incentivize rejuvenating hedgerow management without governmental subsidies.