Ecosystem function in a changing climate

The climate is changing across the globe as a result of human activities1. Atmospheric concentration of greenhouse gases such as carbon dioxide (CO2) are increasing, which has led to an increase in the global mean temperature over the last 100 years1. Climate change also increases the likelihood of extreme weather events1. However, how will various ecosystems respond to these changes? This was the focus of Associate Professor Sally Power, from the Hawkesbury Institute for the Environment (UWS), at her seminar at Macquarie University.

Assoc Prof Sally Power is an ecosystem ecologist, previously working in the United Kingdom on nitrogen deposition and cycling, tropospheric ozone, nitrogen and ozone interactions with drought, and the effects of drought on plant diversity4. She was also involved in the DIRECT Experiment (Diversity Rainfall and Elemental Cycling in a Terrestrial ecosystem), which looked at extreme rainfall events on a mesic grassland in southern England4. She arrived at the Hawkesbury Institute two years ago and has been working on two projects: the DRI-Grass project, and the EucFACE project (Eucalyptus Free Air CO2 Experiment)4.

The DIRECT Experiment

Grasslands provide various ecosystem services (such as carbon storage) but are threatened by climate change, particularly due to changes in rainfall patterns2. For example, in southern England, there is expected to be an overall decrease in annual rainfall, with rainfall occurring in more extreme events2. As discussed by Assoc Prof Power, the DIRECT experiment looks at the responses of a mesic grassland to different rainfall regimes to predict how they will be affected in the future4.

 DIRECT experiment

 DIRECT Experiment – controlling rainfall regimes. Image retrieved from https://workspace.imperial.ac.uk/climatechange/public/pdfs/CAPER_poster.pdf

 

Plant species will vary in their resistance to climate change due to their varying functional traits2. Functional traits include features such as root depth, growth rates, the amount of nitrogen in their leaves, and how quickly they can photosynthesise2. The DIRECT experiment divided plants into 3 distinctive groups:

–          Group 1: Perennial forbs and grasses2,4

–          Group 2: Caespitose (tufted) grasses2,4

–          Group 3: Annual herbs, grasses and some legumes2, 4

The experiment found that perennial plants (which are very important for ecosystem functioning) are quite sensitive to climate change, particularly during times of water stress2. According to Assoc Prof Power, reduced frequency of rainfall events has a large effect on perennial plant species. Hence, annual plants will be required to maintain ecosystem function during drought periods2.

DRI-Grass Experiment

A similar type of experiment is currently being conducted by Assoc Prof Power at the Hawkesbury Institute. This experiment is looking at how changing rainfall regimes will affect grassland ecosystems and root herbivory in western Sydney4.

As stated by Assoc Prof Power, early results indicate that different rainfall regimes have led to changes in soil moisture4. Furthermore, Assoc Prof Power has found species composition changes, such as an increase in the weed Eragrostis curvula (African lovegrass) in wetter environments, a decrease in the weed Setaria sp. (Pigeon Grass) during dry treatments, and summer drought plots solely dominated by the weed Cynodon dactylon (Couch). Although early in the experiment, it is evident that species composition changes in western Sydney grasslands should be expected under climate change in the future.

EucFACE Experiment

Currently there is a major uncertainty of how forests will be affected by an increase in carbon dioxide3. At the leaf level, it is known that an increase in CO2 will lead to increased photosynthesis and reduced water loss3 – but what about at the ecosystem level? This is the focus of the EucFACE experiment at the Hawkesbury Institute – a realistic, long term experiment5 to determine effects of elevated CO2 on an intact Cumberland Plain Woodland System4.

 EucFace experiment

EucFACE Experiment. Image retrieved from http://brewongleeec.com/2013/10/29/eucface-and-future-climates-at-the-university-of-western-sydney/

 

Assoc Prof Power is focussing her research on the effects of soil nutrient cycling in a higher CO2 world, and according to Reich, Hungate & Luo (2006), evidence for Carbon (C) and Nitrogen (N) interactions are rare. This experiment can be looked at as highly significant as C and N play a major role in the metabolism of plants, herbivores and microbes5. According to Assoc Prof Power, increased CO2 could lead to increased nutrient cycling, but it may also cause the down-regulation of nitrogen uptake. Assoc Prof Power’s early results indicate increased CO2 is causing very rapid phosphate releases, which requires further investigation in the near future.

 CO2 output following rain Data from the EucFACE Experiment: After a prolonged period of drought, the CO2 output shows the forest “breathing”. Image retrieved from http://www.uws.edu.au/hie/events_and_seminars/breathe_in,_breathe_out_eucface_and_the_forest_breathing

 

Concluding Points

  • Ecosystems are complex! Their reactions to climate change will vary, and this will change depending on the ecosystem in focus.
  • More research is required into responses of ecosystem functioning with increased CO2, temperature and extreme rainfall events.

References

  1. Cubasch, U., D. Wuebbles, D. Chen, M.C. Facchini, D. Frame, N. Mahowald, and J.-G. Winther (2013). Introduction. In Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung … and P.M. Midgley (Eds.). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
  1. Fry, E. L., Manning, P., Allen, D. G., Hurst, A., Everwand, G., Rimmler, M., & Power, S. A. (2013). Plant functional group composition modifies the effects of precipitation change on grassland ecosystem function. PloS one, 8(2), e57027. doi: 10.1371/journal.pone.0057027
  1. Kauwe, M. G., Medlyn, B. E., Zaehle, S., Walker, A. P., Dietze, M. C., Hickler, T., … & Norby, R. J. (2013). Forest water use and water use efficiency at elevated CO2: a model‐data intercomparison at two contrasting temperate forest FACE sites. Global change biology, 19(6), 1759-1779. doi: 10.1111/gcb.12164
  1. Power, S. (2014, May 14). Drought, deluge and elevated CO2 – a two hemisphere look at ecosystem responses to climate change. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.
  1. Reich, P. B., Hungate, B. A., & Luo, Y. (2006). Carbon-nitrogen interactions in terrestrial ecosystems in response to rising atmospheric carbon dioxide. Annu. Rev. Ecol. Evol. Syst., 37, 611-636. doi: 10.1146/annurev.ecolsys.37.091305.110039

 

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Australia and its environment – an unhealthy relationship

Australia has a poor environmental record2. Since European settlement over 100 species have become extinct, including 27 mammals, 23 birds, 4 frogs and 60 plant species7. Currently there are 1500 mammals, birds, reptiles, amphibians and plants threatened with extinction7. In his seminar at Macquarie University, Professor Corey Bradshaw from The University of Adelaide discussed this dismal state of the Australian environment (with a healthy dash of politics), and the role that scientists need to play in reversing this devastating trajectory.

Habitat loss and degradation is the primary threat to biodiversity worldwide1 – and as mentioned by Prof Bradshaw, Australia is not helping the cause. Since European settlement there has been large scale land use changes3, mostly for agriculture2. This has resulted in 38% forest cover loss in around 200 years2,3. Most vegetation that remains is highly fragmented and/or disturbed3.

 Vegetation extent

Extent of vegetation in Australia: a) Estimated Pre-1750 and b) Present (2001-2004). Image altered from http://www.environment.gov.au/node/22149

 

The threat of feral cats to native mammals in Australia was also at the core of Prof Bradshaw’s discussion. The introduction of feral cats and foxes has led to a huge decline in small to medium sized native mammal species in Australia, including the extinction of 22 mainland species in the last 100 years6. As stated by Prof Bradshaw, the Dingo (Canis lupus dingo) may be the only last hope for ecosystems in Australia to minimise the meso-predator (feral cats and foxes) effects on native mammals. Instead of tackling this problem head on, governments continue to invest $10 million/year to maintain the Dingo/Dog fence2. This not only prevents dingos from being an integral part of ecosystem function in south-eastern Australia, but it is also a barrier to the migration of other animals2.

 Emus at the State Barrier Fence are deflected from farming land

Emu’s at the State Barrier Fence in Western Australia – an example of a barrier to migration. Displayed by Prof Bradshaw in his presentation. Image retrieved from http://www.australiangeographic.com.au/news/2013/02/controversy-over-was-rabbit-proof-fence-plans/

What is our government doing?

Concern has been expressed by Ritchie et al. (2013) about legislative and policy changes that have been made by state governments in recent years, particularly those favouring exploitative use of national parks. There has also been a relaxation of legislation that prevents vegetation clearing, such as on private land7. Bradshaw (2012) states that there needs to be large shifts in environmental policies. Although, with our present government, described by Prof Bradshaw as the environmental Abbott-oir, major policy shifts should not be expected any time soon.

 Tony abbott environment The Abbott-oir. An image from a blog post by Prof Bradshaw. Image altered from http://conservationbytes.com/2014/03/06/abbotts-no-more-parks-vow-a-bad-move/

 

Let’s control the population!

Many of us would believe that the sheer number of humans is the cause of this worldwide unhealthy relationship with the environment, and that population control is the easy answer. However, according to Prof Bradshaw, if a one child policy applied to every person worldwide, at the end of the 21st century there would still be the same amount of people that there is today! Hence, Prof Bradshaw believes that a population focus is not the solution.

 Population growth

 World population growth. Image retrieved from http://scholars-stage.blogspot.com.au/2010/08/notes-on-dynamics-of-human-civilization.html

 

A nuclear tangent

Prof Bradshaw’s discussion also focussed on the massive worldwide fossil fuel addiction – which isn’t contributing too well to the biodiversity crisis. It has been argued by Brook (2012) that nuclear fission can play a significant role in energy supply in the future, alongside significant expansion of renewables. According to Prof Bradshaw and Brook (2012), the use of renewables alone won’t be enough to end fossil fuel reliance. However, the main issue with nuclear power is societal acceptance5. With new technology such as the Integral Fast Reactor (IFR), Prof Bradshaw states that not one single uranium would need to be mined, as it can utilise current nuclear wastes.

What can be done?

Due to the current state of Australia’s environment and politics, scientists simply need to be doing more2. According to Prof Bradshaw, many people may enter the field of ecology because of the many ‘cool’ phenomena to be studied and discovered. However, such scientists need to look at how they can address really big problems such as species conservation2. Prof Bradshaw states that we also need a united, strong scientific voice to directly advocate and lobby governments based on scientific evidence. Furthermore, ecologists need to get their research out into the public domain, as Prof Bradshaw has achieved with his successful blog “Conservation Bytes”.

Top 5 concluding points

  • Australia’s environment is in a bad state.
  • Policy shifts are required, but current environmental protections are being wound back.
  • Population control is not the answer
  • Putting emotions aside, nuclear power may be the only means to minimise global greenhouse gas production
  • Scientists need to unite and form a strong lobbying body to ensure policies are based on current scientific evidence.

References

  1. Baillie, J., Hilton-Taylor, C., & Stuart, S. N. (Eds.). (2004). 2004 IUCN red list of threatened species: a global species assessment. IUCN.
  1. Bradshaw, C. (2014, May 7). Sampling while Australia burns: we need more out-of-the-box approaches for scientists to change the world. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.
  1. Bradshaw, C. J. (2012). Little left to lose: deforestation and forest degradation in Australia since European colonization. Journal of Plant Ecology, 5(1), 109-120. doi: 10.1093/jpe/rtr038
  1. Bradshaw, C. J., Giam, X., & Sodhi, N. S. (2010). Evaluating the relative environmental impact of countries. PLoS One, 5(5), e10440. doi: 10.1371/journal.pone.0010440
  1. Brook, B. W. (2012). Could nuclear fission energy, etc., solve the greenhouse problem? The affirmative case. Energy Policy, 42, 4-8. doi: 10.1016/j.enpol.2011.11.041
  1. Kennedy, M., Phillips, B. L., Legge, S., Murphy, S. A., & Faulkner, R. A. (2012). Do dingoes suppress the activity of feral cats in northern Australia?. Austral Ecology, 37(1), 134-139. doi: 10.1111/j.1442-9993.2011.02256.x
  1. Ritchie, E. G., Bradshaw, C. J., Dickman, C. R., Hobbs, R., Johnson, C. N., Johnston, E. L., … & Woinarski, J. (2013). Continental-Scale Governance Failure Will Hasten Loss of Australia’s Biodiversity. Conservation Biology, 27(6), 1133-1135. doi: 10.1111/cobi.12189

Brood Parasitic Birds: The success of the Shiny Cowbird without mimicry

Obligate brood parasitic birds outsource the time intensive job of maternal care by laying their eggs in the nest of other species1. Sometimes the host is tricked via mimicry into rearing the parasitic chick, and other times a different approach is utilised by the parasitic bird. The disuse of mimicry in the parasitic Shiny Cowbird (Molothrus bonariensis) was discussed by Dr Ros Gloag (from University of Sydney) in her seminar at University of Sydney.

Typically, a parasitic bird can use mimicry as a means to evade host defences1. For example, a cuckoo can mimic a bird of prey so that the hosts will flee the nest, giving the cuckoo free range to lay its eggs1. Cuckoos can also mimic host eggs to avoid removal by the host species1. Furthermore, cuckoos can ‘tune in’ to the hosts communication, with cuckoo chicks replicating the sound of the host chicks1. However, as mentioned by Dr Gloag, not all brood parasites rely on mimicry but they still succeed. This has been seen in the Shiny Cowbird in South & Central America – a generalist brood parasitic bird that doesn’t mimic eggs, and doesn’t provide visual or vocal mimicry1.

 Juvenille cowbird being fed by a sparrow A Shiny Cowbird juvenile being fed by an adult Rufous-collared Sparrow (Zonotrichia capensis). Retrieved from http://en.wikipedia.org/wiki/Shiny_Cowbird

No vocal mimicry in chicks

The House Wren (Troglodytes aedon) is the most common host of the Shiny Cowbird1, and according to Dr Gloag, they have very different calls. It would hence be expected that the House Wren would realise that the Shiny Cowbird is not its own, and reject it from the nest. But quite the opposite occurs. The study by Gloag and Kacelnik (2013) found that the House Wren attended to nests with Shiny Cowbird brood calls 20% more than nests with House Wren brood calls (see Figure 1).

Why would a House Wren attend to a Shiny Cowbirds brood call more than its own chicks? There are multiple hypotheses for this. It is possible that the House Wren is only responding to the extent of sound from the nest, and that call structure does not matter2 (quantity not quality). Furthermore, it is hypothesised by Gloag and Kacelnik (2013) that the Shiny Cowbird call is simulating the call of older House Wren chicks, although this remains to be tested2.

attendance rates Figure 1: Mean attendance rates of the House Wren to nests during the broadcast of fledgling calls. Altered from Gloag and Kacelnik (2013, p. 106)

No vocal mimicry in adults

If the Shiny Cowbirds don’t provide any vocal mimicry, how do they get the host away from the nest to lay? Typically they don’t. In the example of the Chalk-browed Mockingbirds (Mimus saturninus), most Shiny Cowbirds endure a violent mobbing by the Chalk-browed Mockingbirds, whilst at the same time trying to lay their eggs1. In addition, the Shiny Cowbirds will also attempt to destroy any eggs that are already in the clutch – still whilst experiencing the mobbing5. An epic task!

As shown by Gloag et al. (2013), the mobbing actually doesn’t really deter egg laying by the Shiny Cowbirds. However, it does reduce the number of eggs that are broken by the Shiny Cowbirds5. This means that by mobbing the Shiny Cowbirds, the Chalk-browed Mockingbirds will have a higher chance that their eggs will be successfully reared5.

No egg mimicry

As stated before, Shiny Cowbirds don’t mimic the eggs of their host species. So even if a Cowbird lays its egg in the host nest, why wouldn’t it just reject it? This may be explained by the Clutch Dilution Hypothesis as proposed by Sato, Mikamf & Ueda (2010) (see Figure 2) – an evolutionary trade off1.

In a multiple-parasite system there are multiple cases of parasite invasion of the nest, leading to several events of eggs removed or ruined within the clutch3. By having multiple parasite eggs in the nest, there is a lesser chance that the host egg will be targeted in a future attack3. However, if the host removes all parasite eggs, than the host eggs are more vulnerable to future attacks1.

  Clutch dilutionFigure 2: Clutch dilution hypothesis. H refers to host eggs; P refers to parasite eggs. Source: S. Cardenzana

The study of brood parasitism in the Shiny Cowbird has evidently increased understanding of co-evolution between the Shiny Cowbird and its various host species. When experiencing high cases of parasitism, the host species has to therefore develop a trade-off between their own eggs surviving and the rearing of parasitic birds3. Overall this provides an interesting example of where mimicry is not used to parasitise host species, unlike what is typically seen in various cuckoo species.

References

  1. Gloag, R. (2014, April 4). Trickery without mimicry in brood parasitic birds. School of Biological Science Seminar Series. Conducted from University of Sydney, Camperdown, NSW.
  1. Gloag, R., & Kacelnik, A. (2013). Host manipulation via begging call structure in the brood-parasitic shiny cowbird. Animal Behaviour, 86(1), 101-109. doi: 10.1016/j.anbehav.2013.04.018
  1. Gloag, R., Fiorini, V. D., Reboreda, J. C., & Kacelnik, A. (2012). Brood parasite eggs enhance egg survivorship in a multiply parasitized host. Proceedings of the Royal Society B: Biological Sciences, 279(1734), 1831-1839. doi: 10.1098/rspb.2011.2047
  1. Gloag, R., Fiorini, V. D., Reboreda, J. C., & Kacelnik, A. (2013). The wages of violence: mobbing by mockingbirds as a frontline defence against brood-parasitic cowbirds. Animal Behaviour, 86(5), 1023-1029. doi: 10.1016/j.anbehav.2013.09.007
  1. Sato, N. J., Mikamf, O. K., & Ueda, K. (2010). The egg dilution effect hypothesis: a condition under which parasitic nestling ejection behaviour will evolve. Ornithological Science, 9(2), 115-121. doi: 10.2326/osj.9.115

The queen bee and her control of the masses

Honey bees (Apis mellifera) are pretty intelligent little creatures, and are a good model for studying associated learning3. Honey bees are quite capable of associated learning, but sometimes not so capable of aversive learning2. In her seminar at University of Sydney, Dr Vanina Vergoz (from University of Sydney) explained the role of the Queen Mandibular Pheromone (QMP) in preventing aversive learning in honey bees in order to attract worker bees and literally brainwash them to complete certain tasks and have certain behaviours.

Associated and aversive learning

Associated learning refers to an individual responding to a particular stimulus, such as a cat associating food with the opening of a cupboard – the cat runs towards the cupboard to receive its reward. If on the other hand, the opening of the cupboard always triggers a spray with water, will the cat still eagerly come? Probably not. This is aversive learning, whereby an individual will avoid the stimulus as it is seen as a type of punishment.

Associated learning in honey bees

Many studies on honey bees in the past have focussed on appetitive learning3 – this involves presenting an odour to a bee and then providing it with sucrose2. The bee associates the specific odour with the reward, and hence when exposed to the odour, the bee automatically extends its proboscis to receive the reward – a proboscis extension reflex (PER)2,3.

This method can also be used to study aversive learning, which was first explored in honey bees by Vergoz et al. (2007). As explained by Dr Vergoz, instead of rewarding the bees after presenting an odour, the bees receive a mild electric shock. This initiates a sting extension reflex (SER), which is a defensive response in honey bees3. However, in the presence of the Queen Mandibular Pheromone (QMP), bees were unable to make an association between an odour and an electric shock, but could still associate an odour with a reward2. Therefore, in the presence of the queen, aversive learning is typically not seen in honey bees. As questioned by Dr Vergoz, is the queen trying to supress young worker bees from forming an aversion to her? Before answering this, we should look into what QMP actually is.

 Experiment SER

Experiment testing honey bee sting extension reflex (SER). Source: Vergoz et al. (2007)

Queen Mandibular Pheromone (QMP)

Honey bees are sophisticated in their communication – over 50 chemicals are used by honey bees to communicate within the colony1. By communicating with her colony, the queen can control the behaviour and physiology of those in her nest – a form of organisation1. One substance particularly useful for this control is QMP1.

The production of QMP by the queen allows her presence to be known within the colony4, as it entices young workers to tend to her by feeding and grooming her1,4. QMP is collected by these young workers and spread throughout the colony, which prevents the development of ovaries of workers within the colony and hence preventing other workers from reproducing4.

 Bees attending to queen

Worker bees tending to their queen. Source: Beggs et al. (2007, p. 2461)

 

  • The role of dopamine

Dopamine is a compound that is required for aversive learning2,4 and can have a large impact on the learning ability of honey bees3. Dopamine levels can actually decline in the presence of QMP, leading to a suppression of aversive learning2. For example, Beggs et al. (2007) found that bees that were exposed to QMP had significantly lower levels of dopamine in the brain compared to those not exposed to QMP. In addition, Vergoz et al. (2007) found that those bees that were exposed to QMP did not develop aversive learning – it impaired their learning ability.

Why block aversive learning?

It is evident that the queen does advantage from blocking aversive learning, as the workers groom her, feed her and take care of her2, increasing her survival4. Vergoz et al. (2007) proposed that the workers actually don’t enjoy attending to the queen. If aversive behaviour is not blocked, there can be huge ramifications for the queen, such as repelling workers, causing aggression, and possibly leading to the demise of the queen4. So, a worker that doesn’t establish an aversive memory won’t be able to establish a relationship between QMP and negative side effects4. The workers will therefore continue tending to the queen4.

Concluding remarks

Even though the study of neuroscience solely focuses on the brain2, Dr Vergoz stated that the role of QMP affecting worker behaviour and reproduction shows that we need to start looking at the individuals as a whole. New research suggests that the gut and ovaries can influence behaviour2. This emphasises the need to look past the individual components and to a more holistic approach2.

References

  1. Beggs, K. T., Glendining, K. A., Marechal, N. M., Vergoz, V., Nakamura, I., Slessor, K. N., & Mercer, A. R. (2007). Queen pheromone modulates brain dopamine function in worker honey bees. Proceedings of the National Academy of Sciences, 104(7), 2460-2464. doi:10.1073/pnas.0608224104
  1. Vergoz, V. (2014, March 28). The queen, her pheromone and reproductive hegemony in honey bees. School of Biological Science Seminar Series. Conducted from University of Sydney, Camperdown, NSW.
  1. Vergoz, V., Roussel, E., Sandoz, J. C., & Giurfa, M. (2007). Aversive learning in honeybees revealed by the olfactory conditioning of the sting extension reflex. PLoS One, 2(3), e288. doi: 10.1371/journal.pone.0000288
  1. Vergoz, V., Schreurs, H. A., & Mercer, A. R. (2007). Queen pheromone blocks aversive learning in young worker bees. Science, 317(5836), 384-386. doi: 10.1126/science.1142448

 

Mapping deforestation with remote sensing – a case study from Indonesia

Remote sensing utilises satellites to scan the earth and produce maps that are of value to researchers1. The use of remote sensing to quantify environmental change is at the core of the research of Dr Mark Broich from UNSW, which was discussed in his seminar at UNSW. Dr Broich’s discussion focussed on tropical forest loss in Indonesia and Malaysia, and the use of remote sensing data to determine tree cover change2.

Mapping Global Forest Change

There has been rapid progression in the monitoring of humid tropical forests globally2. One example mentioned by Dr Broich is the “Global Forest Change” website produced by Hansen et al. (2013). This website allows the user to zoom into a particular area of the world and determine forest loss and gain from 2000-2012. Hansen et al. (2013) mention that Indonesia had a significant increase in annual forest lost from 2000-01 to 2011-12 (Figure 1). An example location on the website is Riau, Indonesia, which was described by Dr Broich as a deforestation hotspot.

Indonesia deforestation increase Figure 1: Annual forest loss in Indonesia from 2000 – 2012. Source: Hansen et al. (2013 p. 852)

 

Deforestation in Indonesia

Tropical forests are of high value as they provide many ecosystem goods and services1. Furthermore, deforestation and forest degradation is a large source of carbon dioxide emissions1 – putting stored carbon back into the atmosphere, which can have large implications for climate change. Dr Broich stated that 6.5% of forest cover loss in Indonesia is illegal, with approximately 14% occurring in clearing constricted regions. With such rapid forest lost occurring1, it is evident that monitoring deforestation is vital for not only reducing carbon dioxide emissions, but also reducing biodiversity loss.

  • Mapping deforestation

The use of high spatial resolution optical imagery for deforestation mapping in Indonesia has been a challenge in the past due to the persistent cloud cover over Indonesia1,2. However, as mentioned by Dr Broich, these challenges have been overcome. Remote sensing imagery was successfully used to determine the loss of tree cover from both sides of the Indonesian and Malaysian border1,2 (Figure 2). According to Broich et al. (2013), this allows cross border differences to be identified, which may be due to social, economic and political disparities between the two countries.

The study by Broich et al. (2013) found that Intact Forest Landscapes (IFL) was 27% of the study area on the Malaysian side compared to 55% on the Indonesian side. Broich et al. (2013) also found that Malaysian forest closest to the border was more intensively cleared than on the Indonesian side. They suggest that the remoteness of the Indonesian study area may be why it is not as extensively logged as Malaysia – that is, it is less likely to be cleared2. They further suggest that spatial data should be utilised to compare forest accessibility and deforestation to determine how likely an area will be utilised for logging2.

 malaysia indonesian border

Figure 2: Remote sensing data showing tree cover loss (in red) on the Malaysian/Indonesian border. Source: Broich et al. (2013, p. 5750).

 

Concluding thoughts

It may be unlikely that Indonesia will prioritise the conservation of lowland tropical landscapes due to economic demands and social pressures, even though conservation of tropical forests in Indonesia is greatly required3. Nonetheless, remote sensing is a useful technique in monitoring changes in tree cover in the highly diverse forests of Indonesia. This may assist in monitoring areas of high carbon output as well as determining future conservation actions.

References

  1. Broich, M. (2014, March 28). Remove sensing of vegetation cover change and dynamics. School of Biological, Earth and Environmental Science Seminar Series. Conducted from UNSW, Kensington, NSW.
  1. Broich, M., Hansen, M., Potapov, P., & Wimberly, M. (2013). Patterns of tree-cover loss along the Indonesia–Malaysia border on Borneo. International Journal of Remote Sensing, 34(16), 5748-5760. doi: 10.1080/01431161.2013.796099
  1. Gaveau, D. L., Kshatriya, M., Sheil, D., Sloan, S., Molidena, E., Wijaya, A., … & Meijaard, E. (2013). Reconciling forest conservation and logging in Indonesian Borneo. PloS one, 8(8), e69887. doi: 10.1371/journal.pone.0069887
  1. Hansen, M. C., Potapov, P. V., Moore, R., Hancher, M., Turubanova, S. A., Tyukavina, A., … & Townshend, J. R. G. (2013). High-resolution global maps of 21st-century forest cover change. Science, 342(6160), 850-853. doi:10.1126/science.1244693

 

How valuable is Spatial Information Science in species and ecosystem management?

Spatial information science (SIS) is a tool we all use in our everyday lives. Have you ever found a landmark on Google Maps or determined your location using a GPS? These are both elements of SIS. It doesn’t stop there – SIS can also be used to inform the management of various species and ecosystems. In their seminar at Macquarie University, Dr Michael Chang and Dr Alana Grech (both from Macquarie University) described the multiple uses of SIS in species and ecosystem conservation, from terrestrial vegetation mapping to informing the management of marine ecosystems.

Mapping African Olive distribution

The core of Dr Chang’s research is the use of remote sensing data for vegetation mapping1. Remote sensing data is derived from satellites, and can be used to map, monitor and manage vegetation at regional scales2. Satellite images can determine the reflectance of different plant species, and can therefore be used to map distributions of various invasive species, such as woody weeds2.

Cuneo, Jacobson & Leishman (2009) found remote sensing a useful technique for mapping the distribution of the invasive African Olive (Olea europaea ssp. cuspidata) in Cumberland Plain Woodland, an endangered ecological community (EEC) in western Sydney (see images below). Cuneo et al. (2009) used remote sensing data to determine that African Olive infestations occupy 8.5% or 837ha of Cumberland Plain Woodland. Understanding this extent and distribution of African Olives in western Sydney could allow for appropriate management plans to be implemented.

ImageInfestation of African Olive. Image retrieved from: http://www.rbgsyd.nsw.gov.au/science/Evolutionary_Ecology_Research/Ecology_of_Cumberland_Plain_Woodland/woodland_plants/olea_europea_subsp._cuspidata

 

ImageAfrican Olive distribution in a region of Cumberland Plain Woodland. Source: Cuneo et al. (2009, p. 151)

Protected area design

SIS is also a useful tool to evaluate protected area designs4 – those areas that are set aside for the conservation of biodiversity. For example, spatial software was used to inform the rezoning of the Great Barrier Reef Marine Park in 2004 by determining the various activities occurring in the reef, such as commercial uses (trawling areas) and non-commercial uses (recreational fishing)3. Before the rezoning, the protection zones were unevenly skewed towards remote areas, where trawling and other activities were not taking place3,4. According to Dr Grech, this led to a false sense of security, as these areas were not threatened in the first place! The rezoning of the reef in 2004 rectified this – at least 20% of each bioregion (zones with similar ecological features – a total of 70 within the marine park) was listed as a protected area3. This was seen worldwide as a major achievement in the conservation of marine ecosystems3.

Spatial risk assessment

SIS has been used to evaluate the exposure of threatening processes on various marine species and communities through spatial risk assessments4. These risk assessments analyse the distribution of species or communities against the distribution of threatening processes5. As explained by Dr Grech, spatial risk assessments have been used to inform the management of Dugongs (Dugong dugon) and tropical coastal seagrass meadows.

Dugongs

In the Torres Strait Region in northern Australia, there are significant Dugong populations which are of cultural significance to the local Indigenous Australians4,5. Spatial risk assessments have led to the development of management plans4 and enhanced management decisions5, such as the removal of commercial netting, preventing poor quality terrestrial runoff, and consulting with traditional owners about a moratorium on Dugong hunting5.

Tropical coastal seagrass meadows

Spatial risk assessments have been used to determine the cumulative impacts of stresses on tropical coastal seagrass meadows4. This is achieved by mapping the distribution of seagrasses (see image below) against the distribution of key threatening processes such as agricultural runoff, boat damage, trawling, dredging and port developments6.

ImageDistribution of coastal seagrass habitat along the east coast of Australia. Source: Grech, A., Coles, R., & Marsh, H. (2011, p. 561)

 

The use of cumulative impact mapping alone may not however be sufficient to inform species or ecosystem management, as it depends on the significance of habitat being exposed to the threat4. This has led to the use of irreplaceability – a measure of the overall importance of a site4. Areas of high irreplaceability should be prioritised over those that are more replaceable4, such as prioritising an area containing a rare species compared to an area containing a widespread species. Therefore SIS can be used to prioritise management actions due to resource constraints6, leading to a “bang for your buck” approach4.

The overall value of SIS

It appears SIS is very useful in informing management decisions in species and ecosystem conservation in both terrestrial and marine systems. The integration of spatial information science and biological science are vital to ensuring the best possible approaches to species conservation. It would therefore be beneficial to see these two fields integrating further in the future.

References

  1. Chang, M. (2014, April 9). Adding value to research, learning and teaching in biology through spatial information science. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.
  1. Cuneo, P., Jacobson, C. R., & Leishman, M. R. (2009). Landscape‐scale detection and mapping of invasive African Olive (Olea europaea L. ssp. cuspidata Wall ex G. Don Ciferri) in SW Sydney, Australia using satellite remote sensing. Applied vegetation science, 12(2), 145-154. doi: 10.1111/j.1654-109X.2009.01010.x
  1. Devillers, R., Pressey, R. L., Grech, A., Kittinger, J. N., Edgar, G. J., Ward, T., & Watson, R. (2014). Reinventing residual reserves in the sea: are we favouring ease of establishment over need for protection?. Aquatic Conservation: Marine and Freshwater Ecosystems. doi: 10.1002/aqc.2445
  1. Grech, A. (2014, April 9). Adding value to research, learning and teaching in biology through spatial information science. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.
  1. Grech, A., & Marsh, H. (2008). Rapid assessment of risks to a mobile marine mammal in an ecosystem‐scale marine protected area. Conservation Biology, 22(3), 711-720. doi: 10.1111/j.1523-1739.2008.00923.x
  1. Grech, A., Coles, R., & Marsh, H. (2011). A broad-scale assessment of the risk to coastal seagrasses from cumulative threats. Marine Policy, 35(5), 560-567. doi:10.1016/j.marpol.2011.03.003

The role of prey behaviour in marine trophic cascades

Have you seen the YouTube video below, “How wolves change rivers”? This is a pretty amazing example of a trophic cascade: the affect that the top, apex predators can have on lower trophic levels, or vice versa. This example was mentioned by Professor Robert Warner from the University of California in his seminar at Macquarie University. Although Prof. Warner studies marine environments and the affects fishing can have on entire marine ecosystems, this terrestrial example emphasises the complexity of trophic cascades in both types of systems.

The human impact on marine environments is typically seen in the higher trophic levels, or the predator level3 (see diagram of trophic levels below). As Prof. Warner suggested, a trophic cascade can result from the removal of a predator from a system, which may lead to a change in the abundance of the lower trophic species1,3. However, predator loss can also influence the function of the lower trophic species, such as their behaviour3. If the behaviour of lower trophic species is changing, then what is happening to resources below this level?

Food chainSimple marine food chain with three trophic levels

 

Prey behaviour

Predators in all types of systems – freshwater, marine and terrestrial – can cause various prey responses1. For example, prey can alter their activity level and habitat use depending on whether predators are present or absent1. This is a kind of trade off1 – do they collect food or shelter from predators?

In his seminar, Prof. Warner focussed on prey feeding and movement when predators are increased or decreased in a marine ecosystem. In the presence of predators, prey use behavioural mechanisms such as avoidance and increased vigilance, leading to less feeding and changes in their diets4. Prof. Warner has found that prey weigh less in the presence of predators.

Furthermore, Madin, Gaines & Warner (2010) mention that the prey excursion distance (the distance to which the prey leave their shelter for food) can be affected by predator presence/absence. When a predator declines in a system, the prey have a kind of free range over an area, increasing their excursion rates4. The burning question is, would the system just ‘revert’ back to its pristine state when a predator is introduced back into the system?

Prey excursionPrey excursion?

Image retrieved from http://qetza.deviantart.com/art/School-of-Fish-Bus-252847804

 

The study by Madin et al. (2012), which was also discussed by Prof Warner, found this to be the case. Madin et al. (2012) compared various reefs on Line Islands and the Great Barrier Reef, with results indicating prey foraging behaviour returned to the pre-fishing state once predators recovered in the system3. This recovery actually occurred quite quickly3. Although the species studied were not representative of an entire fish ecosystem, the authors believe these results could be widespread – location wise and taxonomically3. These results could have significant implications for conservationists looking to restore marine systems to their pristine or near pristine state3.

The halo effect

It has been discussed that predators can affect the behavioural response of prey, but as Prof Warner discussed, does risk avoidance lead to changes in prey food distributions? According to Madin et al. (2012), the responses of prey to a loss of predators can cascade through the system, eventually affecting the distribution of macro-algae (primary producers)3.

In the presence of predators, herbivores will only graze in their immediate surroundings, leading to changes in distribution of algae and seagrasses – viewed as the halo effect2 (see image below). On the other hand, the absence of predators leads to a homogenous (more even) use of resources4. Hence, it may be common to assume that predator loss leads to an increase in herbivore densities, leading to a decrease in primary producers2. But is this always the case?

haloThe halo surrounding an island can vary due to prey foraging.

Image retrieved from http://www.1770reefcruises.com/

According to Prof. Warner, the predicted flow on effects can change once mesopredators are taken into account. Mesopredators are the prey that prey on smaller prey, particularly new recruits4. An increase in mesopredators will therefore see a decrease in recruits at the lower trophic levels, as well as change their behaviour4. Smaller species will avoid areas where mesopredators are present4. This then leads to an increase in the heterogeneity and abundance of macroalgae4, which can change the entire dynamics of a marine ecosystem.

Putting this into perspective

The complexity of marine ecosystems and the significance of behaviour responses is enormous. Prey behaviour is influenced by many factors – structure of habitat, food resources available, and composition of predators and grazers3. Understanding this type of complexity should have implications for current management of marine areas. This includes fishing practices as well as politically short-sighted government policies such as shark culls.

References

1. Madin, E.M., Gaines, S.D., & Warner, R.R. (2010). Field evidence for pervasive indirect effects of fishing on prey foraging behavior. Ecology, 91(12), 3563-3571. doi: 10.1890/09-2174.1

2. Madin, E.M., Gaines, S.D., Madin, J.S., & Warner, R.R. (2010). Fishing indirectly structures macroalgal assemblages by altering herbivore behavior. The American Naturalist, 176(6), 785-801. doi: 10.1086/657039

3. Madin, E.M., Gaines, S.D., Madin, J.S., Link, A.K., Lubchenco, P.J., Selden, R.L., & Warner, R.R. (2012). Do behavioral foraging responses of prey to predators function similarly in restored and pristine foodwebs?. PloS one, 7(3), 1-9. doi: 10.1371/journal.pone.0032390

4. Warner, R. (2014, March 19). Fear and longing: Predator change and the role of behaviour in marine conservation. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.

Sociality in an Australian huntsman spider: Delena cancerides

With over 44,000 spider species in the world2, how do you pinpoint one species to study? Dr Lynda Rayor, from Cornell University, has done just that, presenting a seminar at Macquarie University on one very unusual spider species – Delena cancerides.

D. cancerides is an Australian huntsman spider within the family Sparassidae3 that exhibits a prolonged sub-social behaviour2. This is quite peculiar considering that, according to Dr Rayor, sociality is rare in spiders other than initial maternal care of egg sacs. Furthermore, the majority of spiders that are social spin webs, which allows the spiders to cooperate on prey capture and reduce their silk costs. However, D. cancerides also exhibits this trait of a tightly associated, long lasting colony, with one very big difference – it does not build webs3.

Image Photo of D. cancerides – an adult female and offspring. Source:  Agnarsson, I., & Rayor, L. S. (2013, p. 896).

The miniature commune

Dr Rayor has observed colonies of 20 to 200 individuals living in a retreat under the bark of Eucalypts, Casuarinas or dead Acacias.  The retreat comprises of a matriarch and her offspring of various cohorts (or ages)3 (see image below). Dr Rayor’s research has shown that individuals will disperse from the colony only once they are sexually mature (approximately 1 year old).

Image

Instars – the different age groups of D. cancerides in the colony. Source: Yip, E. C., & Rayor, L. S. (2013, p. 1162).

The edges of the retreat are sealed with silk at the top and bottom, which according to Dr Rayor, is large enough for the adult female to guard the entrance. This could possibly be a mechanism of protecting the colony and keeping watch, making it hard for predators to access the retreat3.

Next of kin?

Yip et al. (as cited in Yip & Rayor, 2011) determined through allozyme analyses (a type of genetic analysis) of D. cancerides colonies, that most of the offspring were either full or half siblings. Interestingly though, there were actually unrelated spiders in up to half of the colonies studied. Dr Rayor explains that this is possible because spiders can get lost when foraging at night – they go home to the wrong colony! Individuals of less than 6 instars have a greater possibility of being integrated into the new colony. Older spiders are usually seen as a threat and shooed away, or killed.

Image D. cancerides appearing from under the bark of a tree. Source: Yip, E. C., & Rayor, L. S. (2011, p. 1938)

The sibling conundrum

The study by Yip & Rayor (2013) found that younger D. cancerides of 4th to 5th instar were heavier when their older siblings were present – an indication that younger siblings can benefit from the presence of their older siblings.

Dr Rayor has observed older siblings sharing prey with up to 22 of their younger siblings. She states that although this only occurs 5% of the time (which may not seem like much), it is actually quite significant considering this is not a very common occurrence in spider species. Dr Rayor explains that it is less energy intensive if older spiders share their prey than to continually protect it from younger siblings.

However, it may not all be about prey sharing. Yip & Rayor (2013) explain that the heavier weights could be a result of younger siblings scavenging the prey scraps from the older siblings – not prey sharing. This process can also be referred to as a producer-scrounger system, and may be similar to what has been described within the literature as ‘tolerated theft’ by primates.

Such leisurely dispersal

Why does D. cancerides remain in colonies until they are sexually mature before they disperse? There are two major reasons: cost and habitat saturation3.

#1: The very little cost

  • There is no major food competition within the colony, even if the older spiders have to share some prey with their younger siblings3.
  • Offspring can benefit from their mum – she’s very efficient at eliminating predators with her aggressive attitude. This is particularly handy for the youngsters that cannot defend themselves very well3.
  • Individual tolerance to each other (or lack of cannibalism). Dr Rayor’s new research suggests that the lower metabolic rate of D. cancerides means they can survive on low prey availability, leading to a low cannibalism rate amongst this species.

#2: Habitat saturation

There is no spare space for spiders to disperse – retreats are usually 100% occupied. A small spider would find it extremely difficult to secure a retreat that wasn’t occupied. Therefore, waiting until they are larger and more able to defend themselves is a useful tactic3.

Food (or spiders) for thought

With increasing habitat fragmentation and destruction leading to further habitat saturation, could D. cancerides develop a more relaxed strategy to the kids staying at home? Furthermore, Dr Rayor found that as habitat saturation increases, the occupants become larger, as they are best at competing for new resources (survival of the fittest). Does this mean that, in an evolutionary sense, D. cancerides may become a larger species in the future?

References

1 Agnarsson, I., & Rayor, L. S. (2013). A molecular phylogeny of the Australian huntsman spiders (Sparassidae, Deleninae): Implications for taxonomy and social behaviour. Molecular phylogenetics and evolution, 69(3), 895-905. doi: 10.1016/j.ympev.2013.06.015

2 Rayor, L. (2014, March 5). Adaptations for living with cannibals: Evolution of sociality in Australian huntsman spiders. BioSeminar. Conducted from Macquarie University, North Ryde, NSW.

3 Yip, E. C., & Rayor, L. S. (2011). Do social spiders cooperate in predator defense and foraging without a web?. Behavioral Ecology and Sociobiology, 65(10), 1935-1947. doi: 10.1007/s00265-011-1203-5

4 Yip, E. C., & Rayor, L. S. (2013). The influence of siblings on body condition in a social spider: is prey sharing cooperation or competition?. Animal Behaviour, 85(6), 1161-1168. doi: 10.1016/j.anbehav.2013.03.016