Mark G. Anderson

Conserving the stage: climate change and the geophysical underpinnings of species diversity.

Conservationists have proposed methods for adapting to climate change that assume species distributions are primarily explained by climate variables. The key idea is to use the understanding of species-climate relationships to map corridors and to identify regions of faunal stability or high species turnover. An alternative approach is to adopt an evolutionary timescale and ask ultimately what factors control total diversity, so that over the long run the major drivers of total species richness can be protected. Within a single climatic region, the temperate area encompassing all of the Northeastern U.S. and Maritime Canada, we hypothesized that geologic factors may take precedence over climate in explaining diversity patterns. If geophysical diversity does drive regional diversity, then conserving geophysical settings may offer an approach to conservation that protects diversity under both current and future climates. Here we tested how well geology predicts the species diversity of 14 US states and three Canadian provinces, using a comprehensive new spatial dataset. Results of linear regressions of species diversity on all possible combinations of 23 geophysical and climatic variables indicated that four geophysical factors; the number of geological classes, latitude, elevation range and the amount of calcareous bedrock, predicted species diversity with certainty (adj. R2 = 0.94). To confirm the species-geology relationships we ran an independent test using 18,700 location points for 885 rare species and found that 40% of the species were restricted to a single geology. Moreover, each geology class supported 5–95 endemic species and chi-square tests confirmed that calcareous bedrock and extreme elevations had significantly more rare species than expected by chance (P<0.0001), strongly corroborating the regression model. Our results suggest that protecting geophysical settings will conserve the stage for current and future biodiversity and may be a robust alternative to species-level predictions.

Incorporating climate change into systematic conservation planning

The principles of systematic conservation planning are now widely used by governments and non-government organizations alike to develop biodiversity conservation plans for countries, states, regions, and ecoregions. Many of the species and ecosystems these plans were designed to conserve are now being affected by climate change, and there is a critical need to incorporate new and complementary approaches into these plans that will aid species and ecosystems in adjusting to potential climate change impacts. We propose five approaches to climate change adaptation that can be integrated into existing or new biodiversity conservation plans: (1) conserving the geophysical stage, (2) protecting climatic refugia, (3) enhancing regional connectivity, (4) sustaining ecosystem process and function, and (5) capitalizing on opportunities emerging in response to climate change. We discuss both key assumptions behind each approach and the trade-offs involved in using the approach for conservation planning. We also summarize additional data beyond those typically used in systematic conservation plans required to implement these approaches. A major strength of these approaches is that they are largely robust to the uncertainty in how climate impacts may manifest in any given region.

Interactions betweenLythrum salicaria and native organisms: A critical review

Seventy-one articles concerningLythrum salicaria (purple loosestrife), a European herb introduced to North America, were reviewed for evidence of utilization by North American fauna and the effect of loosestrife on native plant species. In contrast to popular claims, 29 species of organisms were found to utilize this plant, and no evidence of species declines due to purple loosestrife were found. Evidence that loosestrife out-competes cattails and other plant species was found to be lacking or contradictory. Thus detailed, quantitative data are needed to understand loosestrifes natural history, population dynamics, and impacts on native ecosystems if we are to effectively manage this plant.

Estimating climate resilience for conservation across geophysical settings.

Conservationists need methods to conserve biological diversity while allowing species and communities to rearrange in response to a changing climate. We developed and tested such a method for northeastern North America that we based on physical features associated with ecological diversity and site resilience to climate change. We comprehensively mapped 30 distinct geophysical settings based on geology and elevation. Within each geophysical setting, we identified sites that were both connected by natural cover and that had relatively more microclimates indicated by diverse topography and elevation gradients. We did this by scoring every 405 ha hexagon in the region for these two characteristics and selecting those that scored >SD 0.5 above the mean combined score for each setting. We hypothesized that these high-scoring sites had the greatest resilience to climate change, and we compared them with sites selected by The Nature Conservancy for their high-quality rare species populations and natural community occurrences. High-scoring sites captured significantly more of the biodiversity sites than expected by chance (p < 0.0001): 75% of the 414 target species, 49% of the 4592 target species locations, and 53% of the 2170 target community locations. Calcareous bedrock, coarse sand, and fine silt settings scored markedly lower for estimated resilience and had low levels of permanent land protection (average 7%). Because our method identifies—for every geophysical setting—sites that are the most likely to retain species and functions longer under a changing climate, it reveals natural strongholds for future conservation that would also capture substantial existing biodiversity and correct the bias in current secured lands. Identificación de Sitios Duraderos para la Conservación Usando la Diversidad del Paisaje y las Conexiones Locales para Estimar la Capacidad de Recuperación al Cambio Climático Resumen Los conservacionistas necesitan un método mediante el cual poder conservar la diversidad biológica mientras permiten que las especies y las comunidades se reorganicen con respecto al clima cambiante. Desarrollamos y probamos tal método, el cual basamos en características físicas asociadas con la diversidad ecológica y la capacidad de recuperación del sitio con respecto al cambio climático, en el noreste de Norteamérica. Mapeamos comprensivamente 30 escenarios geofísicos distintos basados en la geología y la elevación. Dentro de cada escenario geofísico identificamos sitios que estaban conectados por una cubierta natural y que tenían relativamente más microclimas indicados por la topografía diversa y los gradientes de elevación. Hicimos esto al puntuar cada hexágono de 450 ha en la región con estas dos características y al seleccionar aquellos que tuvieron una puntuación >SD 0.5 por encima del puntaje combinado promedio para cada escenario. Nuestra hipótesis fue que estos sitios con altas puntuaciones tuvieron la mayor capacidad de recuperación. Los comparamos con los sitios seleccionados por The Nature Conservancy por sus poblaciones de alta calidad de especies raras y sus ocurrencias de comunidades naturales. Los sitios con altos puntajes capturaron significativamente más de los sitios de biodiversidad de lo que se esperaba por casualidad (p < 0.0001): 75% de las 414 especies objetivo, 49% de las 4592 localidades de especies objetivo y 53% de las 2710 localidades de comunidades objetivo. Los escenarios de lecho rocoso calcáreo, arena gruesa y limo fino tuvieron puntos marcadamente más bajos para la capacidad de recuperación estimada y tuvieron niveles bajos de protección permanente de suelo (en promedio 7%). Ya que nuestro método identifica – para cada escenario geofísico – sitios que tienen mayor probabilidad de retener especies y funciones más tiempo bajo un clima cambiante, revela baluartes naturales para la conservación futura que también capturaría biodiversidad existente sustancial y corregiría el sesgo en tierras que actualmente están aseguradas.

Applying Circuit Theory for Corridor Expansion and Management at Regional Scales: Tiling, Pinch Points, and Omnidirectional Connectivity

Connectivity models are useful tools that improve the ability of researchers and managers to plan land use for conservation and preservation. Most connectivity models function in a point-to-point or patch-to-patch fashion, limiting their use for assessing connectivity over very large areas. In large or highly fragmented systems, there may be so many habitat patches of interest that assessing connectivity among all possible combinations is prohibitive. To overcome these conceptual and practical limitations, we hypothesized that minor adaptation of the Circuitscape model can allow the creation of omnidirectional connectivity maps illustrating flow paths and variations in the ease of travel across a large study area. We tested this hypothesis in a 24,300 km2 study area centered on the Montérégie region near Montréal, Québec. We executed the circuit model in overlapping tiles covering the study region. Current was passed across the surface of each tile in orthogonal directions, and then the tiles were reassembled to create directional and omnidirectional maps of connectivity. The resulting mosaics provide a continuous view of connectivity in the entire study area at the full original resolution. We quantified differences between mosaics created using different tile and buffer sizes and developed a measure of the prominence of seams in mosaics formed with this approach. The mosaics clearly show variations in current flow driven by subtle aspects of landscape composition and configuration. Shown prominently in mosaics are pinch points, narrow corridors where organisms appear to be required to traverse when moving through the landscape. Using modest computational resources, these continuous, fine-scale maps of nearly unlimited size allow the identification of movement paths and barriers that affect connectivity. This effort develops a powerful new application of circuit models by pinpointing areas of importance for conservation, broadening the potential for addressing intriguing questions about resource use, animal distribution, and movement.

Case studies of conservation plans that incorporate geodiversity.

Geodiversity has been used as a surrogate for biodiversity when species locations are unknown, and this utility can be extended to situations where species locations are in flux. Recently, scientists have designed conservation networks that aim to explicitly represent the range of geophysical environments, identifying a network of physical stages that could sustain biodiversity while allowing for change in species composition in response to climate change. Because there is no standard approach to designing such networks, we compiled 8 case studies illustrating a variety of ways scientists have approached the challenge. These studies show how geodiversity has been partitioned and used to develop site portfolios and connectivity designs; how geodiversity-based portfolios compare with those derived from species and communities; and how the selection and combination of variables influences the results. Collectively, they suggest 4 key steps when using geodiversity to augment traditional biodiversity-based conservation planning: create land units from species-relevant variables combined in an ecologically meaningful way; represent land units in a logical spatial configuration and integrate with species locations when possible; apply selection criteria to individual sites to ensure they are appropriate for conservation; and develop connectivity among sites to maintain movements and processes. With these considerations, conservationists can design more effective site portfolios to ensure the lasting conservation of biodiversity under a changing climate.

Assessing Floodplain Forests: Using Flow Modeling and Remote Sensing to Determine the Best Places for Conservation

ABSTRACT: Mature and diverse floodplain forests are among the worlds most diminished ecosystems and conservationists need a rapid method to identify the best remaining examples of these systems. Because large rivers and their dynamics bind the floodplain together, the method must go beyond simple inventory of remnant patches to evaluate flood processes and identify constraints in the surrounding watersheds. We develop such a method for a three million hectare watershed in New England using a combination of data types to evaluate key attributes of floodplain systems. Riparian and floodplain communities were modeled using a GIS analysis of river valley topography and riverine processes, and floodplain forest occurrences were identified in a classification and regression (CART) analysis. Current flooding was verified using overlays of remotely sensed imagery of spring and fall water levels. We evaluated the intactness of the floodplain occurrences using ratios of upstream dam storage to annual runoff, the length of the connected stream network, and the naturalness of surrounding land cover. Field-assigned ranks of forest quality were correlated with the occurrence size, percent verified flooding, and percent natural cover. Predicted quality ranks reinforced the importance of these factors. Results indicate that the twenty top-ranking streams collectively contain 75 high quality areas suitable for floodplain forest restoration and conservation. Independent verification of these areas strongly corroborated our results.

Conserving Forest Ecosystems: Guidelines for Size, Condition and Landscape Requirements

A forest ecosystem consists of thousands of species. Conserving forest biodiversity depends on protecting complete ecosystems that contain the full complement of their associated flora and fauna. Here I present an explicit framework and a set of guidelines for selecting and conserving forest sites as coarse-filters for forest biodiversity. The framework focuses on: 1) Size; defined as the area needed to accommodate natural dynamics and provide sufficient breeding area for multiple pairs of forest interior species, 2) Condition; defined as the quantity of biological legacies, and the amount of non-fragmented interior forest needed to ensure resilience, and 3) Landscape context; defined as the amount and configuration of managed forest cover to maintain regional scale properties, and to buffer and connect key reserve areas. I use a case study from the Northern Appalachians ecoregion to illustrate the development of quantitative thresholds and measurable goals for these characteristics.

The Northern Appalachian/Acadian Ecoregion, North America

The Northern Appalachian/Acadian ecoregion in northeastern United States and southeastern Canada is projected to experience dramatically increased temperatures by the end of the twenty-first century, potentially driving numerous changes in species distributions throughout the region. For species to respond to such changes, landscape-scale conservation planning must result in increased levels of connectivity both within the ecoregion and with neighboring areas. Numerous initiatives have sought to promote ecological health and connectivity throughout all or a part of this ecoregion, particularly Two Countries, One Forest, a binational umbrella organization. Work in the region suggests the need for increased attention to be given to planning for linkages across landscape scales to allow for both short- and long-term movement of species, and for coupling connectivity with efforts to enhance ecosystem resilience throughout the reserve system and the surrounding matrix.

A stream classification system to explore the physical habitat diversity and anthropogenic impacts in riverscapes of the eastern United States

Describing the physical habitat diversity of stream types is important for understanding stream ecosystem complexity, but also prioritizing management of stream ecosystems, especially those that are rare. We developed a stream classification system of six physical habitat layers (size, gradient, hydrology, temperature, valley confinement, and substrate) for approximately 1 million stream reaches within the Eastern United States in order to conduct an inventory of different types of streams and examine stream diversity. Additionally, we compare stream diversity to patterns of anthropogenic disturbances to evaluate associations between stream types and human disturbances, but also to prioritize rare stream types that may lack natural representation in the landscape. Based on combinations of different layers, we estimate there are anywhere from 1,521 to 5,577 different physical types of stream reaches within the Eastern US. By accounting for uncertainty in class membership, these estimates could range from 1,434 to 6,856 stream types. However, 95% of total stream distance is represented by only 30% of the total stream habitat types, which suggests that most stream types are rare. Unfortunately, as much as one third of stream physical diversity within the region has been compromised by anthropogenic disturbances. To provide an example of the stream classification’s utility in management of these ecosystems, we isolated 5% of stream length in the entire region that represented 87% of the total physical diversity of streams to prioritize streams for conservation protection, restoration, and biological monitoring. We suggest that our stream classification framework could be important for exploring the diversity of stream ecosystems and is flexible in that it can be combined with other stream classification frameworks developed at higher resolutions (meso- and micro-habitat scales). Additionally, the exploration of physical diversity helps to estimate the rarity and patchiness of riverscapes over large region and assist in conservation and management.