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Grarock K.,Australian National University | Grarock K.,University of Canberra | Lindenmayer D.B.,Australian National University | Lindenmayer D.B.,National Environmental Research Program | And 2 more authors.
Journal of Environmental Management | Year: 2013

Research indicates that invasion is a multi-step process, where each stage is contingent on the stage that precedes it. Numerous hypotheses addressing the factors that influence each stage of the invasion process have been formulated, but how well does this theory match what occurs in the natural world? We created a general conceptual model for the invasion process based on invasion theory. Using acomposite 41-year data set, we then reconstructed the invasion sequence of the common myna (Acridotheres tristis) to investigate the similarities between invasion theory and this observed invasion. We observed a lag period before population growth of 2.7 (±0.3) years, a maximum rate of population growth of 24.1 (±6.4) birds per km2 per year, a lag period before spreading of six years and an average spreading rate of 0.4km per year. The length and duration of these stages correspond closely with what invasion process theory would anticipate. We suggest that a conceptual model, coupled with basic species, environment and event information, could be a useful tool to enhance the understanding and management of invasions. © 2013 Elsevier Ltd.


Grarock K.,Australian National University | Grarock K.,University of Canberra | Lindenmayer D.B.,Australian National University | Lindenmayer D.B.,National Environmental Research Program | And 2 more authors.
Environmental Management | Year: 2013

Introduced species pose a major threat to biodiversity across the globe. Understanding the impact of introduced species is critical for effective management. Many species around the world are reliant on tree cavities, and competition for these resources can be intense: threatening the survival of native species. Through the establishment of 225 nest boxes, we examined the relationship between tree density and the abundance and nesting success of three bird species in Canberra, Australia. The common myna (Acridotheres tristis) is an introduced species in Australia, and the crimson rosella (Platycercus elegans) and eastern rosella (Platycercus eximius) are native species. We then investigated the impact of common myna nest box occupation on crimson rosella and eastern rosella abundance. Tree density significantly influenced the abundance and cavity-nesting of all three species. Common myna abundance (birds per square kilometer) was greatest at low tree density sites (101.9 ± 22.4) and declined at medium (45.4 ± 10.1) and high (9.7 ± 3.6) tree density sites. The opposite pattern was observed for the crimson rosella, with greater abundance (birds per square kilometer) at high tree density sites (83.9 ± 9.3), declining over medium (61.6 ± 6.4) and low (31.4 ± 3.9) tree density sites. The eastern rosella was more abundant at medium tree density sites (48.6 ± 8.0 birds per square kilometer). Despite the strong influence of tree density, we found a significant negative relationship between common myna nest box occupancy and the abundance of the crimson rosella (F 1,13 = 7.548, P = 0.017) and eastern rosella (F 1,13 = 9.672, P < 0.001) at some sites. We also observed a slight increase in rosella nesting interruptions by the common myna at lower tree densities (high: 1.3 % ± 1.3, medium: 6.6 % ± 2.2, low: 12.7 % ± 6.2), although this increase was not statistically significant (F 2,40 = 2.435, P = 0.100). Our study provides the strongest evidence to date for the negative impact of the common myna on native bird abundance through cavity-nesting competition. However, due to the strong influence of habitat on species abundance and nesting, it is essential to investigate the impacts of introduced species in conjunction with habitat variation. We also suggest one component of introduced species management could include habitat restoration to reduce habitat suitability for introduced species. © 2013 Springer Science+Business Media New York.


Alvarez-Romero J.G.,James Cook University | Alvarez-Romero J.G.,National Environmental Research Program | Adams V.M.,James Cook University | Adams V.M.,National Environmental Research Program | And 20 more authors.
Biological Conservation | Year: 2015

Pursuing development and conservation goals often requires thinking and planning across terrestrial, freshwater and marine realms because many threats and social-ecological processes transcend realm boundaries. Consequently, effective conservation planning must consider the social and ecological links between realms and follow a cross-realm approach to allocate land/water uses and conservation actions to mitigate cross-realm threats and maintain cross-realm ecological processes. Cross-realm planning requires integrating multiple objectives for conservation and development, and assessing the potential co-benefits and trade-offs between them under alternative development scenarios. Despite progress in cross-realm planning theory, few fully-integrated and applied cross-realm plans exist. The gaps between research and implementation are not unique to cross-realm planning, but are accentuated by the complexity of spatial decision-making entailed. Based on a collaborative process including scientists, resource managers and policy-makers, we developed an operational framework for cross-realm planning based on up-to-date thinking in conservation science, but offering practical guidance to operationalise real-world planning. Our approach has a strong theoretical basis while addressing the visions and needs of decision-makers. We discuss the foundations and limitations of current approaches in cross-realm planning, describe key requirements to undertake this approach, and present a real-world application of our framework. © 2015 Elsevier B.V.


Grarock K.,Australian National University | Grarock K.,University of Canberra | Tidemann C.R.,Australian National University | Wood J.T.,Australian National University | And 2 more authors.
Biological Invasions | Year: 2014

Population manipulation of introduced species can be difficult and many widespread eradication or reduction attempts have failed. Understanding the population dynamics of a species is essential for undertaking a successful control program. Despite this, control attempts are frequently undertaken with limited knowledge of the species population dynamics. For example, in Australia, concern over the impact of the introduced common myna (Acridotheres tristis) has led to community members culling the species. In this paper, we assessed the impact of community-led common myna culling program over broad and fine-scales in Canberra, Australia. We utilized a basic population model to enhance understanding of common myna population dynamics and the potential influence of various culling regimes. We found a significant negative relationship between common myna abundance and culling at fine-scales (1 km2). However, over broad-scales the relationship between common myna abundance and culling was not significant. Our population model indicated culling at a rate of 25 birds per km2 per year would reduce common myna abundance, regardless of initial density. Our results suggest that currently too few individuals are being removed from the Canberra population, and natural reproduction, survival and/or immigration is able to replace the culled individuals. This highlights the value of undertaking basic population modeling to assess if potential control measures are capable of achieving desired outcomes. Our work provides information for researchers, government and community groups interested in controlling not only the common myna, but also other introduced species. © 2013 Springer Science+Business Media Dordrecht.


Grarock K.,Australian National University | Grarock K.,University of Canberra | Tidemann C.R.,Australian National University | Wood J.T.,Australian National University | And 2 more authors.
Austral Ecology | Year: 2014

Habitat modification and invasive species are significant drivers of biodiversity decline. However, distinguishing between the impacts of these two drivers on native species can be difficult. For example, habitat modification may reduce native species abundance, while an invasive species may take advantage of the new environment. This scenario has been described as the driver-passenger model, with 'passengers' taking advantage of habitat modification and 'drivers' causing native species decline. Therefore, research must incorporate both habitat modification and invasive species impact to successfully investigate native species decline. In this paper, we used the common myna (Acridotheres tristis) as a case study to investigate the driver-passenger model. We investigated changes in bird abundance, over 2 years, in relation to different habitat types and common myna abundance. We hypothesized that the common myna is both a passenger of habitat change and a driver of some bird species decline. Our results indicated that the abundance of many native species is greater in high tree density nature reserves, while the common myna was uncommon in these areas. Common myna abundance was almost three times higher in urban areas than nature reserves and declined rapidly as tree density in nature reserves increased. Our findings indicated that the common myna is primarily a passenger of habitat change. However, we also observed negative associations between common myna abundance and some bird species. We stress the importance of simultaneously investigating both invasive species impact and habitat modification. We suggest habitat restoration could be a useful tool for both native species recovery and invasive species control. Understanding the drivers of native species decline will help inform impact mitigation and direct further research. © 2013 The Authors. Austral Ecology © 2013 Ecological Society of Australia.


Barton P.S.,National Environmental Research Program | Barton P.S.,Australian National University | Lentini P.E.,University of Melbourne | Lentini P.E.,National Environmental Research Program | And 19 more authors.
Environmental Management | Year: 2015

Substantial advances have been made in our understanding of the movement of species, including processes such as dispersal and migration. This knowledge has the potential to improve decisions about biodiversity policy and management, but it can be difficult for decision makers to readily access and integrate the growing body of movement science. This is, in part, due to a lack of synthesis of information that is sufficiently contextualized for a policy audience. Here, we identify key species movement concepts, including mechanisms, types, and moderators of movement, and review their relevance to (1) national biodiversity policies and strategies, (2) reserve planning and management, (3) threatened species protection and recovery, (4) impact and risk assessments, and (5) the prioritization of restoration actions. Based on the review, and considering recent developments in movement ecology, we provide a new framework that draws links between aspects of movement knowledge that are likely the most relevant to each biodiversity policy category. Our framework also shows that there is substantial opportunity for collaboration between researchers and government decision makers in the use of movement science to promote positive biodiversity outcomes. © 2015, Springer Science+Business Media New York.


Jardine T.D.,National Environmental Research Program | Jardine T.D.,Griffith University | Jardine T.D.,University of Saskatchewan | Bond N.R.,Griffith University | And 22 more authors.
Ecology | Year: 2015

Biotic communities are shaped by adaptations from generations of exposure to selective pressures by recurrent and often infrequent events. In large rivers, floods can act as significant agents of change, causing considerable physical and biotic disturbance while often enhancing productivity and diversity. We show that the relative balance between these seemingly divergent outcomes can be explained by the rhythmicity, or predictability of the timing and magnitude, of flood events. By analyzing biological data for large rivers that span a gradient of rhythmicity in the Neotropics and tropical Australia, we find that systems with rhythmic annual floods have higher fish species richness, more stable avian populations, and elevated rates of riparian forest production compared with those with arrhythmic flood pulses. Intensification of the hydrological cycle driven by climate change, coupled with reductions in runoff due to water extractions for human use and altered discharge from impoundments, is expected to alter the hydrologic rhythmicity of floodplain rivers with significant consequences for both biodiversity and productivity. © 2015 by the Ecological Society of America.


PubMed | National Environmental Research Program
Type: Journal Article | Journal: Environmental management | Year: 2015

Substantial advances have been made in our understanding of the movement of species, including processes such as dispersal and migration. This knowledge has the potential to improve decisions about biodiversity policy and management, but it can be difficult for decision makers to readily access and integrate the growing body of movement science. This is, in part, due to a lack of synthesis of information that is sufficiently contextualized for a policy audience. Here, we identify key species movement concepts, including mechanisms, types, and moderators of movement, and review their relevance to (1) national biodiversity policies and strategies, (2) reserve planning and management, (3) threatened species protection and recovery, (4) impact and risk assessments, and (5) the prioritization of restoration actions. Based on the review, and considering recent developments in movement ecology, we provide a new framework that draws links between aspects of movement knowledge that are likely the most relevant to each biodiversity policy category. Our framework also shows that there is substantial opportunity for collaboration between researchers and government decision makers in the use of movement science to promote positive biodiversity outcomes.

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