New study points to the global significance of the Plains-wanderer

Can you spot Australia's most unique bird?
Terrick Terrick National Park
Photo: John Morgan

The Plains-wanderer has for some time been known to be a member of Australia’s ancient avifauna and its nearest, albeit distant, relatives are seedsnipe from South America.  It is the sole member of a Family of birds called the Pedionomidae. It's a species typically confined to native grassland habitats in eastern Australia and, unfortunately, one of the most endangered species of those grasslands. It should be a flagship for conservation and new research tells us why!

Recently, Jetz et al. (2014) published a major review of the world’s 9,993 recognised bird species to determine which species we can least afford to lose in the current extinction crisis if maximum global phylogenetic diversity is to be maintained.  Phylogenetic diversity is a measure of biodiversity which incorporates phylogenetic difference between species and phylogenetic analyses have become essential to research on the evolutionary tree of life. The concept of phylogenetic diversity has been rapidly adopted in conservation planning.

Jetz et al. (2014) developed a hierarchy based on how isolated a species is on the phylogenetic tree which they termed ‘evolutionary distinctness’.  They also included global geographic range, and global endangerment in their metrics.  The summary metric that Jetz et al. (2014) used to rank the world’s birds combines evolutionary distinctness and extinction risk. 

By their calculation, the Plains-wanderer is ranked:
 #1 among Australian birds and #4 in the world!!

As such, these analyses highlight we can ill-afford to lose the species, yet current data suggest that significant declines are being observed, and it's not entirely clear why.

The two strongholds of the Plains-wanderer are the semi-arid (or xeric) native grasslands of the Riverina region of NSW and Victoria’s Northern Plains.  Monitoring in NSW during 2001-2012 has found that the population size has declined by 75% during droughts, then recovered slightly during benign years, and was then recorded at record low levels during the very wet years of 2011-12.  The population has remained at very low levels for over a decade, and this is cause for considerable concern. In Victoria there has been monitoring on Terrick Terrick NP and nearby private land over five years (2010-14).  Numbers declined by >90% during 2011-12 in the wet years (perhaps because breeding was negatively affected, while thickening of grasslands has reduced occupyable habitat) and the numbers have remained at historically low levels.

If ever there was a need to monitor the dynamics of a species of conservation concern, whilst also monitoring its habitat suitability and key determinants of mortality risk (e.g. predation),  then the Plains-wanderer would seem an essential candidate species. Good, basic scientific research is needed to answer simple questions: how long do birds live; are population dynamics cyclic; can suitable habitat be successfully created from scatch? In some respects, a metric of the success of grassland conservation and management will be that species like the Plains-wanderers can be maintained in their habitat, and that their numbers grow rather than decline.

Thanks to David Baker-Gabb for alerting me to the evolutionary distinctiveness of the Plains Wanderer, and for providing information on the population trends of this species.

Reference

Jetz, W, Thomas, G H, Joy, J B, Redding, D W, Haartmann, K and Mooers, A.  2014.  Global distribution and conservation of evolutionary distinctness in birds.  Current Biology (2014), http://dx.doi.org/10.1016/j.cub.2014.03.011.

A new population curve for prehistoric Australia

The arrival of Aboriginal people in Australia marked an important change in the continent's ecology. The loss of the mega-fauna and a rise in the use of fire are common themes that resonate when discussing the role of Aboriginal people in shaping the nature of Australia.

Up until now, most of the discussion has been about when aboriginal people arrived. The numbers fluctuate between 40,000 and 100,000 yrs ago, with a convergence of opinion in recent years (because of better carbon dating techniques) that it was probably about 52,000 yrs BP.

An interesting paper by Williams take this insight one step further.

Using radiocarbon dating techniques on >1700 sites from all over Australia, Williams has tried to reconstruct/assess population growth rates in Australia up until the time of European contact.

Using some modelling assumptions about the initial founder effect (that is, how many people first colonised), he interprets three key things:

1) Australia was settled by thousands, not just a handful, of humans, suggesting deliberate rather than accidental colonisation of the continent. The research suggests that it probably would have taken 1000 to 3000 people to reach the numbers of Aboriginal people observed at time of European contact.
2) the population size grew very slowly - constrained by glacial periods. It wasn't until the Holocene (from about 10,000 yrs BP) that the population grew substantially. The study shows during the glacial maximum 18,000 to 21,000 years ago, the population fell dramatically. The data suggests 60% of the population was lost during this time, a period of extreme dry and cold. It took 9000 years for the population to recover to the same levels.
3) the maximum population size before European settlement was approx. 1.2 M people (assuming a founder population of 1000-2000). This occurred only 500 years ago.



Distribution of archaeological sites contributing radiocarbon data to the study by Williams.
You can see there is a pretty good coverage across Australia.



You can see this population reconstruction clearly here in this figure from the paper. The effects of 'founder size' (how many people might have first colonised Australia) has a big effect on population size at the time of European contact, as does climate. The two graphs show the outcomes based on different model assumptions - they give pretty much the same results. They suggest that population growth really took off at about 12,000 yrs BP; this corresponds with increasing climate stability

This paper (along with others - see here) hints that the big changes in vegetation and mega-fauna extinctions observed in the last 50,000 yrs were probably driven by climate. Landscape burning by Aboriginal people has been linked to significant changes in the geographical range and demographic structure of many vegetation types but there is now an emerging lack of congruence between human activity and fire records during the period 20-40 kya. During a period of consistently low human populations, as posited by Williams, it is difficult to reconcile how Aboriginal people could have had the profound impacts that have been speculated by many.

I can't vouch for the veracity of the work reported by Williams, but it provides interesting food for thought when interpreting the recent history of Australia.


References
Williams (2013) A new population curve for prehistoric Australia. Proceedings of the Royal Society B 280, 20130486.

Sakaguchi et al. (2013) Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia. Proceedings of the Royal Society B 280: 20132182

Ecological Rants

I just discovered Charley Krebs Blog page called "Ecological Rants". It's worth a look.

Krebs is an excellent ecologist who has written one of the best textbooks on ecology (Ecology: The Experimental Analysis of Distribution and Abundance) and, because of his age, has been around long-enough to have seen the field both stagnate, get bogged down and ultimately, make some massive gains about the understanding of the natural world. I've always thought his insights were interesting, even if I don't always agree with him.

There's excellent 'rants' about:
- answering unanswerable questions
- when academics should retire
- conservative politics and science
- biodiversity research
- science and money
- what bureaucrats need to do to let scientists get on with their job

I really like Charley's approach (elder statesman type of thing) and it's great to see (once again) how Blogs can get scientists to reach out to other scientists (and the public) beyond their academic publications.

Shrubs in woodlands - directional or cyclic?

One of the things that ecologists have noticed in (some) grassy woodlands in southern Australia over the last two decades is that woody cover has been on the rise. This can take the form of increases in shrubs (such as Leptospermum spp., Acacia spp.), or dense regeneration of trees.

My own work (and that of my students and other scientists) show this increase might be due to changes in management (such as the removal of stock grazing from long-grazed forests upon reservation for nature conservation), altered fire regimes (usually a decline or exclusion of fire), overgrazing by native and exotic herbivores (that reduce competition from the ground-layer vegetation, as well as encouraging unpalatable species at the expense of palatable ones), and potentially even changes in atmospheric CO2 levels that favour woody plants over grasses.

Increases in woody plants have been recorded at several locations in southern Australia. This increase has generally been thought to be a uni-directional change that requires management intervention to alter this trajectory. So, at Wilsons Promontory National Park for instance, dense thickets of native Tea Tree that have established in swale grasslands and woodlands over the last 40 years are now being actively managed by carefully timed fire to open up the closed shrublands to benefit biodiversity and amenity.

Parks Victoria staff undertaking a burn to manage Coast Tea Tree (Leptospermum laevigatum) at Wilson's Promontory NP
(Photo: Greg McCarthy)

Just the other day, however, I saw evidence that woody plant encroachment isn't always uni-directional.

Herb-rich woodlands at Langi Ghiran
in mid-winter, before flowering.

At Langi Ghiran, there are fabulous herb-rich woodlands. Spring is a sight to behold - indeed, some of the highest species richness levels in Australia have been recorded there. Shrubs appear to be localised and generally sparse.

Hedge Wattle (Acacia paradoxa), a shrub native to the system, began spreading about a decade ago at this site and forming thickets. I'm not sure why it did this - was it climatically stimulated, was there a change in grazing pressure form native herbivores, was this a response to rising CO2?

It established prolifically in the inter-tree gaps, which are common in this woodland (and support much of the plant diversity), and establishes in the absence of fire. It also seems pretty unpalatable to the resident kangaroos and wallabies. I began to think that the end game here would be dense stands of wattle, a decline in diversity, and a landscape transformed visually.

However, when I last visited, the scene had changed a little bit.

Hedge Wattle - the dead looking stuff in the centre of the image - at
Langi Ghiran, 22nd June 2014.

Across 10's of hectares, Hedge Wattle had died, or was senescing. I'm pretty sure this was not because of old age - most shrubs are (and this is just a guess) less than 15 yrs old. We know from work by my Honours student Julia Franco that Hedge Wattles can live for five decades.

Where plants were not quite dead, the phyllodes were brown and desiccated and clearly the individuals looked like they were on the way out.

I first noticed this browning off in summer after a hot and dry spell. Now, in mid-winter, there seems no signs of recovery. This hints (to me) that drought has probably played a key role in the population dynamics of Hedge Wattle at this site. It hints that the population might be cyclical - assuming that the rise and fall of Hedge Wattle has occurred before, but just gone un-noticed.

If this is the case, it suggests a few important lessons:
- long-term observations can help decipher directional versus cyclical patterns in nature.
- if drought is at play here, was this drought 'extreme' and hence, might we expect its frequency (and potential effects) to increase over time?
- drought plays a key role in the dynamics of many woody plant populations but its effects are sometimes under-appreciated.

What else might be going on?? It's probably important to survey Hedge Wattle at Langi Ghiran to see if mortality is linked to particular aspects, slopes or soil types. Perhaps it is exacerbated in close proximity to century old trees. Might smaller plants be more susceptible than older ones (because they have less extensive root systems)? What about density? Are dense populations more or less susceptible to desiccation as individuals compete strongly for water?

Whatever the cause, this site illustrates that woody plant encroachment doesn't always end in permanent site occupation. Trying to figure out where it does would improve our understanding of both the process, and the management response.

Building community-based monitoring

Latrobe students quantifying the effects of fire
in the Little Desert NP.
(Photo: John Morgan)

I teach undergrad Botany and Ecology at La Trobe University. My university has a really good reputation for training field-based biologists, and many of our graduates are now making great contributions to conservation through their work in ecological consultancies, local government, government research organisations, NGOs, environmental education and parks management. Many of the undergrads I teach, particularly the mature-aged students, have a real passion for the natural world and really know that they want to make a difference.

As part of my outreach activities, I also engage with local community groups - such as Friends Groups (like my local group called Holly Hill Revegetation Group), local plant groups (e.g. Australian Plant Society), Landcare Groups and naturalist societies. This is also really rewarding - here's a bunch of (mostly) amateur enthusiasts wanting to making their local environment better, and protect what little bits we have left by taking an active interest in their management. Unlike the university students I teach, many of these people don't know much about biology and ecological principles. I see my role here as one of educating to ensure better outcomes.

Engaging with the "community" is a crucial way to get them interested in natural systems and harness their desire to do positive things. We've done this well on many fronts. One thing that is really taking off amongst these community groups is the field of citizen science monitoring. Here, local people are keeping tabs of environmental change in their local area, often doing excellent work that universities and governments are unable to do. WaterWatch is a good example of a programme that relies on volunteers to assess water quality in local catchments.

This is a great way to engage with people. But is it useful as a scientific activity to improve management by changing land management practices, i.e. learning by doing and then adapting management? I don't want to get into semantics about the quality of data that is collected, or the motivations of people who collect data. I'm more interested in thinking about "what is useful monitoring" and how to we maximise the benefits we get from such monitoring.

I've been musing about this a little because I'm often asked to help design monitoring for community groups, knowing full well that such monitoring, to be useful, needs to be simple, long-term and consistent. Here's a couple of suggestions that might help us think about what useful monitoring might be.

1) Identify the 'problem' first! The best monitoring has a clear question(s) / objective in mind from the outset that really determines what the monitoring should be and how it should be undertaken. Importantly, the information gained from the monitoring should help establish better practices in the future rather than just documenting change.

Planting Buloke trees into ex-pasture
(Photo: John Morgan)

Here's a simple example. Your local Landcare Group is revegetating some upper slopes box ironbark woodlands and will plant tubestock to establish trees. Your main concern is the need for weed control in the initial establishment phase because you've observed that establishment success seems patchy in previous years. Hence, it would seem logical to (a) plant some trees into intact understorey and (b) plant some trees where you've sprayed the understorey out. You count the number of individuals in each area then return yearly to recount the trees to assess survival. A more nuanced monitoring would record tree height to see if plants are also growing faster where there are no competitors in the initial phases. This might seem an obvious "experiment" but it is worth monitoring because the outcomes would really help us better use our resources - should we spray weeds out  or if we don't need to spray, can we plant more trees. This monitoring might highlight where the real problem lies too. Trees might do really poorly in both areas because of herbivores, or low soil moisture per se, hence allowing us to design better plantings in future. While this monitoring may not be that "exciting" to do, it is very useful.

2) Keep it simple! When thinking about monitoring, the best information tends to be that which addresses Primary Questions. I tend to think of ecological questions as exiting in a hierarchy that span from Primary, Secondary and Tertiary level questions. Here's an example, about mistletoes.

Mistletoes are really important in woodland and forest ecosystems in Australia because they are food and habitat for a whole heap of birds and animals, and have important roles to play in nutrient turnover. Hence, if I was an restoration practitioner who had been planting trees in agricultural landscapes for connectivity, habitat enhancement, etc, I'd be keen to ask the following (hierarchical) questions:

Dropping Mistletoe
(Photo: http://davesgarden.com/guides/pf/showimage/189316/)

Primary: Are mistletoes naturally colonising revegetation plantings?
Secondary: Does distance to nearest patch of remnant vegetation affect whether mistletoes are colonising reveg plantings?
Tertiary: Are mistletoes more numerous on some reveg tree species than others?

Hopefully you can see here that the Primary Question, about whether mistletoes are colonising plantings, is probably the most important question to ask first. It is probably also a pretty simple question to answer with monitoring: go out to XX planting sites and search for mistletoe colonisation on trees. Record which plantings have them. The information derived from this exercise informs us about their capability to recolonise reveg plantings, and from this we can start to understand the Secondary and Tertiary Questions. However, there is no need to ask the latter questions if the answer to the Primary Question is "No". You can see from this example, the monitoring could be very simple - there is not need to complicate things initially. Resurveying plantings 3-5 yrs later would then tell us about whether the situation is stable or changing.

3) Archive data somewhere!  Citizen science is a great concept, but for it to be useful, the data that is collected needs to be stored somewhere that is accessible into the future. Importantly, the data needs to be used periodically to inform understanding and leverage decision making processes.  Most ecologists who study long-term dynamics do so knowing that dynamics will span decades. In Australia, there are ecological experiments that have now been going for many years (in some cases 50-100), but they are only valuable because the data is archived and can be accessed for future comparison. Indeed, the new Terrestrial Ecological Research Network (TERN), a federal government initiative, is almost entirely about databasing old and new data. This will be a great resource for scientists over the coming century if it can be maintained. A similar approach is needed for citizen science.

This might span a range of scales. If your local bush group is into collecting information about birds and plants, perhaps by annual surveys, then this data is most useful if archived in national databases where such records already occur. The Atlas of Living Australia (ALA) is a superb repository for such data - species location records are a powerful way of observing changes over time. Because these databases are free to access, they really are an excellent place to put your data (which you can then always access) and they allow others to profit from your hard work. Imagine 25 years of bird count data, collected from across Melbourne, being in the ALA and accessible for all. It would give a great overview of the status of native birds in a rapidly growing city. Indeed, such databases are already contributing to this understanding. WaterWatch is an excellent example of collecting data and archiving it as an online resource - it's worth checking out.

Of course, there are much smaller scale ways of archiving data. In local Friends Groups, perhaps the group nominates a 'data manager' and their role is to report annually on what data was entered into their local database. If this was minuted each year, it would be pretty easy to know what was being monitored and where that data resided. I often think it would be great if I could access dates of burning of native grasslands where local groups have now been monitoring them for years. Sadly, such data is not being kept.

This returns me to my original thoughts - be clear about what it is you are monitoring, and why? If it is just to engage with local communities, let's not call it monitoring. Let's call it scientific outreach where we teach people how to monitor. But if we are to monitor, let's do it well and have a clear reason for doing it. And let's use the information being collected to make better environmental decisions.