New book: Monitoring threatened species and ecological communities

A new book is coming that aims to improve the standard of monitoring for Australia’s threatened biodiversity and I had the opportunity to contribute to one of the chapters:

Chapter 21: Determining trends in irruptive desert species

Summary:

Populations of many desert-dwelling organisms show ‘boom and bust’ dynamics, irrupting briefly following rain-driven pulses of productivity before collapsing again to low numbers. Determining population trends for such organisms poses unique challenges. This chapter describes population booms and busts in two species of dasyurid marsupials monitored over 22–27 years at nine sites in arid central Australia and uses these species to gain insight into how population trends in irruptive species might be discerned. The brush-tailed mulgara Dasycercus blythi increased predictably after heavy rainfall at all sites before again becoming scarce, whereas the lesser hairy-footed dunnart Sminthopsis youngsoni fluctuated asynchronously at all sites, with no population drivers identified. These disparate patterns indicate that monitoring programs (survey timing, number and placement of monitoring sites) should be designed with respect to the natural history of the target species to reveal trends in their populations. Environmental factors and known or putative threats to the target species also should be monitored, and appropriate models to assess the robustness of population trends and key drivers should be constructed to assist in making decisions about management intervention. More resources and input from stakeholders are needed to lift monitoring of threatened, irruptive desert species above current levels.

Reference:

Dickman C. R., Greenville A. C. & Wardle G. M. (2018). Determining trends in irruptive desert species. In: Monitoring threatened species and ecological communities (eds S. Legge, D. B. Lindenmayer, N. Robinson, B. Scheele, D. M. Southwell and B. Wintle) pp. 281-92. CSIRO Publishing, Melbourne.

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New paper: Save Australia’s ecological research

Long-term research has revealed that ‘booms’ in productivity from extreme rainfall events also bring risks from introduced predators in Australian desert environments. Photo by Aaron Greenville

I was one of 69 authors on a letter published in Science calling for Australia to save its Long Term Ecological Research Network (LTERN). The network comprises more than 1100 long-term field plots within temperate forests, rainforests, alpine grasslands, heathlands, deserts, and savannas, with an unparalleled temporal depth in biodiversity data.  We are now experiencing some of the greatest ecological change that humans have ever experienced, and now, more than ever, Australia needs to expand its capacity in biodiversity monitoring, not end it. The decommissioning of LTERN will also end Australia’s ability to contribute to the International Long Term Ecological Research Network. On a personal level, LTERN was the only mechanism within Australia for early career researchers to develop their careers in long term research.

The letter has been featured in a news piece in Science titled: “Australia to ax support for long-term ecology sites” and Nature titled: “Ecologists protest Australia’s plans to cut funding for environment-monitoring network“.

Hopefully, the decision to decommission LTERN will be reversed, as ecological processes work on longer time scales than the traditional 3 to 5 year  funding cycles.

Reference:

Lindenmayer D., Burns E. L., Dickman C. R., Green P. T., Hoffmann A. A., Keith D. A., Morgan J. W., Russell-Smith J., Wardle G. M., Gillespie G. R., Cunningham S., Krebs C., Likens G., Pauw J., Troxler T. G., McDowell W. H., Catford J. A., Hobbs R., Bennett A., Nicholson E., Ritchie E., Wilson B., Greenville A. C., Newsome T., Shine R., Kutt A. S., Tulloch A., Thurgate N., Fisher A., Auty K., Smith B., Williams R., Fox B., Metternicht G., Bai X., Banks S., Colvin R., Crane M., Dovey L., Fraser C., Foster C., Heinsohn R., Kay G., Ng K., MacGregor C., Michael D., O’Loughlin T., Portfirio L., Robin L., Salt D., Sato C., Scheele B., Stein J., Stein J., Walker B., Westgate M., Wilson G., Wood J., Venn S., Vardon M., Legge S., Costanza R., Kenny D., Burnett P., Welsh A., Moore J., Sgrò C. & Westoby M. (2017). Save Australia’s ecological research. Science 357, 557.

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New paper: Top predators constrain mesopredator distributions

Authors: Thomas M. Newsome, Aaron C. Greenville, Duško Ćirović, Chris R. Dickman, Chris N. Johnson, Miha Krofel, Mike Letnic, William J. Ripple, Euan G. Ritchie, Stoyan Stoyanov & Aaron J. Wirsing.

Published in: Nature Communications

Abstract:

The dingo is one of Australia’s top-predators. Photo by Bobby Tamayo.

Top predators can suppress mesopredators by killing them, competing for resources and instilling fear, but it is unclear how suppression of mesopredators varies with the distribution and abundance of top predators at large spatial scales and among different ecological contexts. We suggest that suppression of mesopredators will be strongest where top predators occur at high densities over large areas. These conditions are more likely to occur in the core than on the margins of top predator ranges. We propose the Enemy Constraint Hypothesis, which predicts weakened top-down effects on mesopredators towards the edge of top predators’ ranges. Using bounty data from North America, Europe and Australia we show that the effects of top predators on mesopredators increase from the margin towards the core of their ranges, as predicted. Continuing global contraction of top predator ranges could promote further release of mesopredator populations, altering ecosystem structure and contributing to biodiversity loss.

Reference:

Newsome, T.M., Greenville, A.C., Ćirović, D., Dickman, C.R., Johnson, C.N., Krofel, M., Letnic, M., Ripple, W.J., Ritchie, E.G., Stoyanov, S. & Wirsing, A.J. (2017). Top predators constrain mesopredator distributions. Nature Communications, 8: 15469.

Media:

Newsome, T.M. Thinking big gives top predators the competitive edge. The Conversation, May 2017.

Strom M. Reintroducing dingoes can help manage feral foxes and cats, study suggests. Sydney Morning Herald, 23rd May 2017.

Schwing E. Study: To Mitigate Problem Predators, Give Wolves More Space, Tolerance. The Northwest News Network, 23rd May 2017.

Dingoes need more space to fight off pests, study finds. Australian Geographic, 24th May 2017.

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New paper: 75 years of dryland science

Authors: Aaron C. Greenville, Chris R. Dickman and Glenda M. Wardle

Published in: Plos One

Abstract:

Research gaps in global dryland literature: Research gap distance matrix heat-map (red = high, clear = low) on global dryland literature. The greater the metric the higher the dissimilarity between topics.

Growth in the publication of scientific articles is occurring at an exponential rate, prompting a growing need to synthesise information in a timely manner to combat urgent environmental problems and guide future research. Here, we undertake a topic analysis of dryland literature over the last 75 years (8218 articles) to identify areas in arid ecology that are well studied and topics that are emerging. Four topics — wetlands, mammal ecology, litter decomposition and spatial modelling, were identified as ‘hot topics’ that showed higher than average growth in publications from 1940 to 2015. Five topics — remote sensing, climate, habitat and spatial, agriculture and soils-microbes, were identified as ‘cold topics’, with lower than average growth over the survey period, but higher than average numbers of publications. Topics in arid ecology clustered into seven broad groups on word-based similarity. These groups ranged from mammal ecology and population genetics, broad-scale management and ecosystem modelling, plant ecology, agriculture and ecophysiology, to populations and paleoclimate. These patterns may reflect trends in the field of ecology more broadly. We also identified two broad research gaps in arid ecology: population genetics, and habitat and spatial research. Collaborations between population genetics and ecologists and investigations of ecological processes across spatial scales would contribute profitably to the advancement of arid ecology and to ecology more broadly.

Reference:

Greenville A.C., Dickman C.R. & Wardle G.M. (2017). 75 years of dryland science: trends and gaps in arid ecology literature. Plos One, 12: e0175014.

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New paper: Science on a micro-budget

What happens when one of your hobbies and work collide? A short article in Science!

I am sort of obsessed with astrophotography and try to obtain the best quality and quantity of data I can to make my images of some faint and distant object in the night sky. This results in me fine-tuning my equipment and spending long nights imaging under the stars. However, I need to find time to sleep as well. After all, I have a day job as an ecologist. So I have been semi-automating my system in order to let it run for the entire night on its own and while I get some sleep.

IMG_20160514_145537

Arduino-based cloud sensor, with infrared thermometer to measure the sky temperature and ambient temperature sensor (black cable).

I stumbled across a user group that make their own cloud sensors (amongst other equipment) and thought this could be an interesting project to try. If clouds are detected, an alarm could be sent to my mobile phone and wake me up in time to pack or cover up my gear before getting wet and damaged. The cloud sensor is based on the Arduino, an open-source micro-controller and electronics platform. By combining temperature sensors and some coding, I can monitor for clouds. It works by measuring the sky and ambient temperature and at some threshold, the different between the two indicates cloud. You can find my code on GitHub.

There are many environmental sensors that are available for the Arduino and user-friendly groups to get you started. This is also true for the Raspberry Pi, an open-source micro-computer platform. Both the Arduino and Raspberry Pi run open-source software, which is easy to learn and already familiar to some scientists (e.g. Python). Nathan (aka @ecotechnica) had experience with the Raspberry Pi, so we teamed up to explore how open-source hardware and software could be used in science to help reduce research costs.

Fig-1-Two-Micro-controllers

The two leading open-source hardware platforms: (A) The Arduino Uno (US$23), which has 16 MHz micro-controller with 32 kb of memory, plus 14 digital input/output pins and six analog pins to connect it to sensors and other components. (B) The first generation Raspberry Pi model B board included Ethernet and USB ports for connectivity. The current (2016) model B board (US$35) now includes integrated Bluetooth (v4.1) and wireless networking (802.11n).

We found that a wide range of devices can be made, such as weather stations, automatic watering systems for crops, high-altitude balloons for astronomy, remote camera systems, GPS tracking systems and laboratory automation equipment. All systems could be built at a fraction of the cost of their commercial equivalents. There was another advantage. Designs and code can be easily shared and even published along-side scientific reports or as separate publications, further improving transparency and repeatability of experiments.  Imagine been able to build the same piece of research equipment, with the exact components and run the same code that collects data in previous experiments! This is all possible with open-source hardware platforms, such as the Arduino and Raspberry Pi.

This all may sound a bit complicated and hard, but remember I was able to build a cloud sensor from instructions already published and modify the code to suit my needs. I also was able to write a driver in Visual Basic to interface the the cloud sensor to my imaging software. I have very little soldering, electronics or even coding experience. Now for the next open-hardware project!

Reference:

Greenville, A.C. and Emery, N.J. (2016). Gathering lots of data on a small budget. Science, 353: 1360-1361.

See Nathan’s blog post for more.

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New paper: Spatial and temporal synchrony in reptile population dynamics in variable environments

Authors: Aaron C. Greenville, Glenda M. Wardle, Vuong Nguyen and Chris R. Dickman.

Published in: Oecologia

Abstract:

Resources are seldom distributed equally across space, but many species exhibit spatially synchronous population dynamics. Such synchrony suggests the operation of large-scale

The panther skink (Ctenotus pantherinus) from the Simpson Desert, Australia.

The panther skink (Ctenotus pantherinus) from the Simpson Desert, Australia.

external drivers, such as rainfall or wildfire, or the influence of oasis sites that provide water, shelter, or other resources. However, testing the generality of these factors is not easy, especially in variable environments. Using a long-term dataset (13–22 years) from a large (8000 km²) study region in arid Central Australia, we tested firstly for regional synchrony in annual rainfall and the dynamics of six reptile species across nine widely separated sites. For species that showed synchronous spatial dynamics, we then used multivariate follow a multivariate auto-regressive state–space (MARSS) models to predict that regional rainfall would be positively associated with their populations. For asynchronous species, we used MARSS models to explore four other possible population structures: (1) populations were asynchronous, (2) differed between oasis and non-oasis sites, (3) differed between burnt and unburnt sites, or (4) differed between three sub-regions with different rainfall gradients. Only one species showed evidence of spatial population synchrony and our results provide little evidence that rainfall synchronizes reptile populations. The oasis or the wildfire hypotheses were the best-fitting models for the other five species. Thus, our six study species appear generally to be structured in space into one or two populations across the study region. Our findings suggest that for arid-dwelling reptile populations, spatial and temporal dynamics are structured by abiotic events, but individual responses to covariates at smaller spatial scales are complex and poorly understood.

Reference:

Greenville A.C., Wardle G.M., Nguyen V. & Dickman C.R. (2016). Spatial and temporal synchrony in reptile population dynamics in variable environments. Oecologia, 182: 475–485.

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New paper! Population dynamics of desert mammals: similarities and contrasts within a multi-species assemblage

Authors: Aaron C. Greenville, Glenda M. Wardle, Vuong Nguyen and Chris R. Dickman.

Published in: Ecosphere

Abstract:

A mulgara from the Simpson Desert, Qld, Australia.

A mulgara from the Simpson Desert, Qld, Australia.

Understanding the temporal and spatial dynamics of species populations remains a key focus of population biology, providing vital insight into the drivers that influence demography and into sub-populations that are vulnerable to extinction. Across regional landscapes, spatially separated sub-populations may fluctuate in synchrony, or exhibit sub-structuring due to subtle differences in local intrinsic and extrinsic factors. Using a long-term dataset (17‑22 years) obtained from a large (8000 km²) study region in arid central Australia, we tested firstly for regional synchrony in annual rainfall and the dynamics of five small mammal species across nine widely separated sites. Using Moran’s theorem, we predicted that the spatial correlation between the regional sub-populations of these species would equal that between local density-independent conditions (annual rainfall).

For species that showed synchronous spatial dynamics, we then used multivariate state-space (MARSS) models to predict that regional rainfall would be positively associated with their populations, whereas species with asynchronous sub-populations would be influenced largely by other factors. For these latter species, we used MARSS models to test four hypotheses. These were that sub-population structures: 1) were asynchronous and governed by local site-specific factors, 2) differed between oasis and non-oasis sites, 3) differed between burnt and unburnt sites, and 4) differed between three sub-regions with different rainfall gradients. We found that the spatial population dynamics of our study small mammals differed between and within families. Two species of insectivorous dasyurid marsupials showed asynchronous dynamics that most likely tracked local conditions, whereas a larger carnivorous marsupial and two species of rodents had strongly synchronous dynamics. These latter species exhibited similar spatial correlations to local and regional rainfall events, providing evidence that the Moran effect operates for some, but not all, species in this arid system.

Our results suggest that small mammal populations do not respond in similar ways to shared environmental drivers in arid regions, and hence will vary in their responses to climate change. As arid lands globally are predicted to face climatic shifts that will exacerbate rainfall-drought cycles, we suggest that future work focuses on exploring these responses at different spatial scales across multiple dryland taxa.

 

Reference:

Greenville, A. C., G. M. Wardle, V. Nguyen, & C. R. Dickman. 2016. Population dynamics of desert mammals: similarities and contrasts within a multi-species assemblage. Ecosphere 7:e01343. 10.1002/ecs2.1343.

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