29 November 2013

Getting out and about, it depends on how dense you are

In which we look at how possum home range is influenced by density.

I have just been home for lunch and found an infestation of 16 year old boys at my house. Most had just completed their last school exam for the year and come to see my son and hang out. All 12 of them! Usually my sons are either on their own or have a friend of two with them when they are at home. When Dad lectures animal behaviour it is always an opportunity to see some of the actions that I teach and research in, well, action. When my sons are on their own they tend to do things like x-boxing, shooting hoops in the driveway, raiding the fridge, play music, watching telly, facebook, annoying brothers/mother/father/cats as they roam around various parts of the house. Sometimes they will leave the house to visit a friend or go to the gym. Add a friend at home and you get similar behaviours but with slightly less movement around the house and less of a likelihood for visiting other friends. When you have an infestation level of 16 year olds you get quite a change in behaviour. The boys tend to congregate in the games room playing pool, xbox or out on the driveway shooting hoops. The boys seldom move into the rest of the house and they seldom leave the property in a big group to visit friends (presumably because most of the friends are here and because not many houses can cope with so many large teens). With my animal behaviour glasses on it looks like the density of the population affects the movement behaviour of the boys.

In the wildlife management business, we almost always are concerned with changing the densities of animal populations: reducing density of pests and increasing the densities of threatened species. One of the difficulties involved in altering densities is when behaviours change when numbers in an area drop. One pest species that we spend a lot of time in trying to reduce in numbers is the brush-tailed possum. This Australian species was introduced into New Zealand over one hundred years ago and has grown to a population in the tens of millions which does enormous damage to native diversity. Possums also carry bovine tuberculosis and can spread the disease through cattle. Hence, possums are public enemy number 1 in New Zealand and are controlled (a polite kiwi way of saying slaughtered) in vast numbers around the country. As we have gotten better at controlling possum populations we have become interested in what happens to their behaviour as population densities decrease.
Possum control seeks to preserve native areas

Belinda Whyte has just completed a PhD in the Centre for Wildlife Management and Conservation at Lincoln University. Belinda's research directly examined possum behaviour in populations of different density and her first paper, with her advisors James Ross and Helen Blackie, has been published in Wildlife Research. Belinda's research was mostly centred in the Malvern area of central Canterbury. She had two sites which had low possum densities (1-2/ha) and one site with high densities (7/ha). Live-trap cages were placed in the sites and possums were captured and fitted with GPS collars that allowed Belinda to follow the movement of the individual over the following months. Three times a week individuals were tracked to their den sites (areas where they slept during the day). Population density seemed to make a difference. The two low density sites had possums that behaved similarly to each other but both differed from the high density site. At the low density sites possums had much larger home ranges (9-12 ha compared to 2 ha), more home range overlap (26% compared to 6%) and more den sites (4 compared to 3) than high density possums. So, in low densities possums tend to move around further, potentially interact more with other possums and have several places of safety. These outcomes have important implications for control. By reducing a possum population you will have fewer individuals that can carry and spread TB or eat your favourite native bird species eggs. However, this gain is tempered by the fact that surviving possums will forage further afield, potentially coming in contact with more cattle, and that they are more likely to bump into neighbouring possums and spread the disease amongst the surviviors. So while controlling possums is a useful thing to do it is not as effective as it could be because they change their behaviour as densities decline.

So teenage boys and possums seems to have some behaviours in common! Home range behaviours change depending on density of the local population. Let's just hope that urine marking of territory is not one of those behaviours in common or I might not want to go back to my den tonight.

21 November 2013

Saving the planet, one bottle of wine at a time.

This blog post was written by postgraduate student Michael Fake as part of the course, Research Methods in Ecology (Ecol608). Michael revisits a Lincoln University research area that looks at increasing pollinators in vineyards published in 2012.

We have entered a period of global declines in both managed and wild pollinator species abundance. If this is not setting off alarm bells in your head it should, as over 30,000 plant species are dependent on pollinators, including a third of the world’s food crops. Pointing fingers gets tricky as more than one factor is involved. However, it is without a doubt that habitat loss due to human activity is the most significant detrimental factor to global pollinator diversity.

“Pollinator habitat enhancement: Benefits to other ecosystem services” is a recently published paper which addresses the finer points of the ecosystem services provided by enhancing pollinator habitat. Wratten and colleagues draw attention to the fact these habitats are useful for more than just pollination. They provide a myriad of potential services that should be considered when weighing up the pros and cons of potential Agri-Environmental Schemes.

These schemes are already in use in both Europe and America. Many aim at enhancing pollinator conservation and activity by encouraging the establishment of resource rich habitats in agricultural systems. They are frequently reinforced with monetary subsidies and technical guidance for their overall planning and management. It’s in land owners best interests to adopt these pollinator enhancing schemes.

As a budding viticulturist and ecologist, I believe New Zealand viticulture is prime territory for such schemes. Vineyards have already been proven to benefit from increased functional biodiversity in the system. For example, the use of selected cover crops can reduce both pest activity and disease pressure as well as a number of other services. On the whole, however, conventional viticulture is that of monocultural crop production, and there exists much room, both figuratively and literally, for improvement in regards to enhancing and harnessing biodiversity in vineyards.

Check out these websites for a more comprehensive view of vineyard agro-ecology.

Pyramid Valley Vineyards, a first-rate Bio-dynamically managed vineyard and winery from North Canterbury. Agri-environmental schemes would not only help our premium boutique producers continue to attract world attention, but could also result in the creation of more places like this. Image source: personal collection.
Bees and other arthropods benefit from habitat enhancement which results in landscapes of high habitat-connectivity and enhanced diversity in structure and species. This is evident as cropping systems in close proximity to natural or semi-natural habitat have increased flower visitation rates compared to un-connected systems. Increasing pollinator diversity not only increases yield, but also facilitates conservation of uncommon plants that share pollinators with widespread plant species.

Marlborough: New Zealand's largest viticultural region is dominated by vineyards, mostly of Sauvignon Blanc, yet remnant horticultural and cropping industries are scattered across the region. Source: "Marlborough" 41'47'08.52" S and 173'53'50.91" E. Google Earth. March 1, 2013.

Those of you who are botanically savvy will know that grapevines are self-pollinating; therefore enhancing pollinator activity may seem counter-intuitive. But that is really the point. We should begin to think of the effects that our actions will have outside property boundaries. It is likely that vineyards currently serve to reduce pollinator species diversity and activity, as they provide little in terms of food or shelter. Neighboring pollinator-dependent industries stand to benefit from habitat enhancement, as do surrounding native ecosystems through facilitation of ecosystem function. This research highlights many of these potential benefits, as well as biodiversity conservation, soil and water quality protection and rural prosperity and aesthetics. The implementation of AES in NZ viticulture can provide the beginnings of sustainability; not only of the industry itself, but also that of the environment.

Having experienced NZ viticulture first-hand, I know that many winegrowers want to be environmentally sustainable. Viticulture, however, like any other industry is driven by cash and profits. Keeping the bean counters happy means that in many cases less than ideal land is developed, or complex vineyard blocking systems are implemented to cover the greatest possible area to maximize yield/ha. Poor-quality land, such as water-logging-prone soils, can produce yields of poor quality and quantity with higher susceptibility to disease. Poorly designed blocking systems can mean improper trellis tension resulting in poor canopy management and subsequent vine damage.

I won’t get too much into details, but the increased disease pressure and suboptimal ripening of the crops basically this all spells reduced quality in the pursuit of quantity. AES schemes, if in place, would mean that these areas would not have to be developed. The subsidy would go some way as to cover the costs from reduced yields and the ecosystem services provided by the reserved area would return benefits, both financial and otherwise, to the wider system. These proposed changes would also have a larger effect on the greater NZ wine industry: shifting to quality over quantity parallels the long-term aims of the NZ wine industry of producing premium and truely sustainable, world-class wines.

10 November 2013

Green fingers getting a hand on Christchurch

This blog post was written by postgraduate student Catherine Hosted as part of the course, Research Methods in Ecology (Ecol608). Catherine revisits a Lincoln University research area that looks at urban ecology in Christchurch published in 2010.

After getting involved with the current Land Use Recovery Plan for Christchurch, an interest for Urban Ecology began brewing. Much of the new plan seems based on the economic vision of Christchurch and I began to worry about the ecology of our urban environment. Just as it seemed Mother Nature was creeping its way back into the concrete crevices, urban development is poised to strike back.

But do not fear! I began to delve into the wonders of Google and found that there is a fight for the maintenance and enhancement of Christchurch’s ecology (such as the Natural Environment Recovery Programme) and the role it will have in the new Christchurch, and it’s looking positive.

Proposed Blue print of the Central City, note the expansion of green networks to current green spaces

First, let me enlighten you with the help of work by Lincoln researchers Glenn Stewart, Maria Ignatieva and Colin Meurk into the world of urban ecology and, more specifically, urban ecological networks.

To start with urban ecology has multiple meanings, be it for landscape architectures (seen as visual connections) or landscape ecologists (seen to provide connectivity for wildlife in fragmented landscapes). The concept isn’t a new fad; it’s been around for centuries. In the past the natural environment shaped settlements and in turn, ecological networks dominated. With the arrival of the industrial revolution man-made structures dominated, sweeping natural features and green spaces under the concrete carpet. In many cities green space was a result of wealth or religious statements.  And for other areas these spaces were the ‘leftovers’ of indigenous forests that avoided destruction and managed to sneak into urban infrastructure. 

The 70’s brought a smell of change in the air: an environmental movement. This movement changed the thinking of urban development to incorporate a more sustainable and green approach to urban living. Greenbelts and green fingers (ecological "fashion accessories") running through and around city landscapes began popping up globally. In the USA, greenbelts encouraged migration routes for wildlife and enhanced biodiversity. The smart developers also utilised these greenbelts as a form of public access- creating the term greenways. 

New Zealand followed the trend and begun to develop many of these ‘hip’ multitasking urban ecological networks. Even so, many of New Zealand’s cities still lack a broader vision of integrated ecological networking.
 There is growing interest in the use of novel sustainable design solutions (Check these out!) as well as a huge potential for utilising neglected lands (e.g. brownfields) as stepping stones for an ecological network . To create modern ecological networks, there must be an integration of progressive technology and sustainable practices at different scales.

An example of a green wall: one of the new types of ecological networks
And so it seems that Christchurch's shake up (no pun intended....) has given the opportunity for improved urban ecological networking. With the destruction of much of the past urban area, a huge potential for the creation of modern ecological network has arisen. It seems that papers, such as Ignativea et al, have been heard by the urban developers of Christchurch. The current NERP (Natural Environment Recovery Programme) produced to coincide with the LURP (Land Use Recovery Plan) aims to identify ways to rehabilitate and improve the natural environment through the rebuild.NERP'S main goal is to restore the natural environment to a level that can support biodiversity and economic prosperity as well as reconnecting people to our amazing natural features. They aim to make the most of available land (mainly brownfield) to create more forests, parks, gardens and integrate with stormwater and wastewater treatment. To add to this exciting potential, recent research by Glenn Stewart has shown that native biodiversity might not struggle in the battle with concrete and non-native species.  This research suggests that over 750,00 native tree, shrubs and other plants have been planted and successfully established over the last decade or so. Thanks to the resurgence in interest of or indigenous flora and fauna, these plants have a good chance to expand into a mixed-origin urban forest. If this is so, then what a great contribution that will be to the ecological networking and biodiversity of the garden city.

The urban ecological networking future is looking good for Christchurch, let's just hope these great ideas come to fruition.

07 November 2013

A Different Angle on Anglers

This blog post was written by postgraduate student Veronica Frans as part of the course, Research Methods in Ecology (Ecol608). Veronica revisits a Lincoln University research area that look at the value of recreational fishing in the Rangitata published in 2004.
Many believe that it is the scientist who comes up with the evidence to support saving a given resource.  However, to win a conservation battle in the political field, one needs to look at all angles.  For Lincoln University’s Geoff Kerr and Glen Greer, focusing on the economic value of the Rangitata River in Canterbury was just the right ticket to get a move on.  In particular, they cast a line at recreational fishermen; although environmental factors were also regarded, as it was the everyday person who was the key to solving a conservation conflict.

The Rangitata River, by Jock Phillips
The Rangitata River flows from the Southern Alps and is 120 km long, where it ends at the Pacific Ocean in between Ashburton and Timaru on the East Coast of South Island.  The river is used by many for irrigation, swimming, kayaking, boating, bird watching, fishing and other purposes.  In 1999, New Zealand Fish and Game applied for the Canterbury Regional Council to create a Water Conservation Order for the Rangitata River, but it had yet to be done.  A Water Conservation Order is an official recognition by the Minister of the Environment that a particular water body holds some intrinsic or utilitarian value.  Once this recognition is in place, restrictions on its use would also apply.  This would protect the area in a way that would maintain the stated value, making it a powerful document in terms of conservation.  So in order for some water plan to be drafted for this river, its importance first needed to be defined.  In response to this, Lincoln’s two professors looked into the economic value behind protecting it.

For the economic value to be assessed, the research team phoned angler homes in the year 2000.  They asked them about the number of times they visited the river, the distance and costs for travel and how much was spent on gear.  It was found that anglers spent some $1100 on about 16 fishing trips to the Rangitata per year.  Mid-Canterbury anglers spent about 65% of their time fishing the Rangitata, while those from south Canterbury spent 59% and others spent 36%.  In central South Island alone, there were ~1560 licensed anglers, including 1060 from north Canterbury who fished at Rangitata.  Basing the survey on 44,000 visits and 36,000 angling days per year, they calculated that some $3 million a year is spent on fishing at Rangitata.

What would you do with 3 million dollars?  Well, the better question is what would you do if you lost it?  Geoff and Glen found that if the quality of the Rangitata and fish stocks were compromised, anglers would travel elsewhere for a better bite and Canterbury’s economy could lose that amount, if not more.  Although salmon and trout have been found to have negative impacts on native New Zealand species, recreational fishing has constituted a great part of the economy.  Fishing activities only represented two thirds of what people use the Rangitata for, so if other groups that could be potentially impacted by the river's degradation were included, it was predicted that further financial consequences would occur.

Since the publication of their paper, a Water Conservation Order for the Rangitata River was finally made in 2006.  A tribunal report in 2002 quoted the final evaluations and financial implications from the survey and Geoff Kerr was also one of the many witnesses for the case.  It was not only the effort of Lincoln University and their research that won the case, but also the efforts of many other organizations and entities as well.

The Rangitata River is the second most heavily fished river for salmon and the third highest fished throughout New Zealand.  If it weren’t for these stakeholders—people who care and travel up to 250 km for a cast and are enthusiastic about it—this river wouldn’t be protected the same way it is today.  To the anglers out there: thank you for fishing and hope you get a big one next time.

“The Salmon Looms,” by Simon Bisson.

More information on Rangitata can be found here.

04 November 2013

Puzzling colours

This blog post was written by postgraduate student Elleni Vendras as part of the course, Research Methods in Ecology (Ecol608). Elleni revisits a Lincoln University research area that look at why leaves change colour in autumn published in 2002.

Travelling in early autumn through the South Island of New Zealand, made me wonder whether the changing trees I see are native. Most trees with autumn leaf colors seem strikingly familiar to the ones in Europe — an almost unnatural contrast to the green natives here. I found that, indeed, very few natives lose their leaves, and the majority of New Zealand native trees are evergreen.

Eurasian aspen at Lake Tekapo
Photo by Elleni Vendras

Deciduous trees lose their leaves in preparation for a cold winter (or dry season in the tropics). They don’t photosynthesize over winter when there is not enough water or sunlight for this oxygen and glucose generating process. The chlorophyll in the leaves breaks down and the components move to the stem and branches of the tree.

What happens next is the reason why so many people travel to places like Wanaka, Mackenzie Country, Waitaki Valley, and Central Otago (and of course New England in the United States as the most popular place for autumn coloration). They take delight in watching the beautiful autumn coloration: carotenoids – yellow and orange pigments, become visible once all the green chlorophyll is gone. These light-absorbing pigments play a role in photosynthesis and act as a photoprotector for the chlorophyll. Another pigment anthocyanin is responsible for the red autumn coloration. It is produced from glucose during autumn and as a result, leaves from maple, aspens and many others turn into a beautiful red.

But, hold on. Why would a tree use energy in producing color pigments in leaves that eventually fall off and wither away? To please Homo sapiens? Certainly not. Scientists believe that these pretty pigments might keep the leaves alive longer by lowering the freezing point and protecting the chlorophyll from photo damage. In that way the leaves might stay longer at the tree and valuable components like glucose or nitrogen can get removed from them and be transported into branches and stem, rather than getting lost with the falling leaves. Others say that anthocyanin may prevent other plant species from growing where the leaves have fallen and decayed.

Besides the physiological meaning of autumn colors, Hamilton and Brown advanced in 2001 a hypothesis on the adaptive significance of autumn leaf colors. They proposed that the yellow and red colors in leafs are a signal of the defensive commitment against autumn colonizing aphid species. This theory aroused scientific argument and was refuted a year after publication by David Wilkinson and colleagues, including the Lincoln University-based author, Steven Wratten.
They stated that the time of the signal is inappropriate since aphids tend to colonize their host BEFORE leaves fall, so while they are still green and have no anthocyanins produced yet. So why hasn't evolution allowed for leaves to defend themselves just in time? Other studies argue that yellow color actually attracts aphids; some insect traps are even yellow colored.  Also it is found that aphids tend to colonize at varying levels on red and yellow leaves depending on the time of the year.

Another argument they made was that the changing of leaf colors are strongly environmentally regulated and not linked to insect colonization. Hamilton and Brown’s theory that bright autumn coloration serves as an honest signal of the trees defensive abilities does not convince the criticizing authors especially when it comes to the cost of honesty. This term which is often used in animal behavior research certainly can be used for plants as well. It describes that communication signals need to be costly to be honest and so honest signals have to be handicaps. Otherwise, there’s no reason not to cheat. But, in fact, there is no extra cost for a tree to reveal yellow leaf color.

So how about red autumn coloration, since this signal is produced in autumn? Are red pigments with their antioxidant abilities just used as another sunscreen complementing the already available yellow carotenoids? Another alternative explanation for their presence offered by the authors is that red leaves absorb more light and energy allowing photosynthesis to happen under harsh conditions.
Red anthocyanin in an leaf of trident maple (Acer buergerianum)
Photo by Elleni Vendras
It’s amazing that something simple that we look at each year is still not well understood. The jury is still out on aphids and red leaves. Marco Archetti found out that aphids tend to avoid red-leaved apple trees and are less fit than those on green leaves. London-based scientists revealed that although aphids lack a red photoreceptor, they may be able to differentiate between green and red leaves and certainly find yellow leaves the most attractive. While in carnivorous plant species the red anthocyanins tend to attract insects. What a confusing mess of contradictions! But that’s science for you. The journey to the truth rarely follows a straight line.
And so scientists continue to do what they have always done: research and debate. Either way, trees in New Zealand can count themselves lucky. While they have to cope with 122 aphid species, trees in Poland have to fight 500 more. By the way, in those latitudes autumn colors are much more striking as well.