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I read somewhere that 1,000 square metres of grass absorbs the same amount of carbon dioxide that one person produces. I then think about my small 10ha property. Does that mean that I am covering 100 peoples’ CO₂ emissions every day? What about those large 1,000ha properties then? Do they absorb thousands of tonnes of carbon every year?
In New Zealand, your average carbon footprint will be around four tonnes of carbon, emitted per year (based on the carbon contained in 16.9 tonnes of carbon dioxide equivalent annual per-capita emissions). A 1,000-square-metre area of grass will take up around one tonne of carbon per year. So if you didn’t fly much, lived in a well insulated home, cycled to work etc, you might bring your overall footprint down to around one tonne of carbon per year, the equivalent of what a backyard lawn may take up per year. So far so good.
The big problem (causing tremendous confusion even among scientists) begins right here. In the above, we talk about fluxes, not pools. Using your bank account as an analogy, fluxes are transfers, pools are balances.
With your own carbon emissions, regardless whether they are one or four tonnes per year, you pay into the atmosphere’s account every year. This means that there is more and more carbon in the atmosphere.
That carbon comes from fossil fuels – an entirely different “account”. Regardless of whether you have 1,000 or 100,000 square metres, this is what grass is doing in this analogy: it takes carbon from the atmosphere every year, but that carbon is going straight back to where it was taken from when you mow the lawn and the biomass is broken down and returned to the atmosphere. In other words, your carbon footprint is a flux that leads to a permanent change in a pool (the atmosphere). This is a bit like a weekly salary. You don’t have to pay it back. What your lawn is doing however, is making payments that are returned a few weeks or months later (when you mow the lawn, a cow eats the grass, or when natural turnover takes place).
The bottom line is that short-term fluxes (as large as they might be) don’t matter if they are reciprocated by an equivalent but opposite flux. If you want, let’s do the experiment. You pay $1,000 onto my account ever odd week, and I pay $1,000 onto yours every even week. None of us will care – as little as the atmosphere will worry about the carbon that your grass patch briefly locks away from it.
So your grass won’t lock away carbon dioxide from the atmosphere in the long run. Neither will any grassland in New Zealand.
If you wait long enough, things can become a bit more complicated, namely if my payments back to you start to become a little less or a little more, causing dollars or carbon to accumulate on one account rather than the other. While this is the case in some ecosystems, such as a growing forest, New Zealand grassland is unlikely one of them. So your backyard isn’t helping, there is no way around reducing our greenhouse gas emissions.
It may not look like a pristine expanse of Amazon rainforest or an African savannah, but the patch of bush at the end of the street could be one of the only places on the planet that harbour a particular species of endangered animal or plant.
Our newly published global study of the conservation value of landscapes in 27 countries across four continents has found these small patches of habitat are critical to the long-term survival of many rare and endangered species.
It tends to be the smaller patches of vegetation that go first, making way for a housing development, a freeway extension, or power lines. Despite government commitments to enhance the vegetation cover of urban areas and halt species extinctions, the loss of vegetation in Australian cities continues.
This story plays out all over the world day after day. Of course, it’s not just an urban story. Patches of rural vegetation are continually making way for, say, a new pivot irrigation system or a new mine to provide local jobs.
Mostly, policymakers and scientists do not consider these losses to be, on their own, a fatal blow to the biodiversity of a region or country. Small, often isolated patches of vegetation are considered expendable, tradeable, of limited ecological value due to their small size and relatively large amount of “edgy” habitat. Wrong.
Research forces a rethink
Our study analysed the relationship between conservation value of vegetation patches and their size and isolation in landscapes across Europe, Australia, North America and Africa. The findings prompt a rethink of long-held views about the relative importance of small, isolated habitat patches for biodiversity conservation. We show that these patches often have unique ecological and environmental characteristics.
That’s because they are the last patches left over from extensive clearing of flat, fertile land for agriculture or urban growth close to rivers and bays. They often contain habitats for rare or endangered species that have disappeared from the rest of the landscape. This makes these small, isolated patches of habitat disproportionately important for the survival of many species.
Our study calls for a rethink of urban planning and vegetation management regulations and policies that allow small patches of vegetation to be destroyed with lower (and often zero) scrutiny. We argue that the environment is suffering a death by a thousand cuts. The existence of large conservation reserves doesn’t compensate for the small patches of habitat being destroyed or degraded because those reserves tend to contain different species to the ones being lost.
The combined impact of the loss of many small patches is massive. It’s a significant contributor to our current extinction crisis.
A key variable used in decisions on vegetation-clearing applications is the size of patch being destroyed. Authorities that regulate vegetation management and approve applications are more permissive of destruction of small patches of vegetation.
This is partly due to a large body of ecological theory known as island biogeography theory and subordinate theories from metapopulation ecology and landscape ecology. These theories suggest that species richness and individual species’ population sizes depend on the degree of isolation of the patch, its size and the quality of the habitat it contains.
While it is crucial that we conserve large, intact landscapes and wilderness, the problem with conserving only large and well-connected patches of high-quality vegetation is that not all species will be conserved. This is because some species exist only in small, isolated and partially degraded habitats, such as those characteristic of urban bushlands or remnant bush in agricultural areas.
For this reason, we highlight the importance of protecting and restoring habitats in these small isolated patches. And these areas do tend to be more vulnerable to invasion by weeds or feral animals. If the impacts of invasive species are not managed, they will eventually lead to the destruction of the habitat values and the loss of the species those habitats support.
Small and isolated patches of vegetation on the urban fringe are under enormous pressure from human use, pets, escaped seed of Agapanthus and the many other invasive species we plant in our gardens. These plants spread into local bushland, where they outcompete the native plants.
Communities can make a difference
As well as these perils, being on the urban fringe also brings opportunity. If a remnant patch of vegetation at the end of the street is seen to be of national environmental importance, that presents a great opportunity to channel the energies of community groups into conserving and restoring these patches.
A patch that is actively cared for by the community will provide better habitat for species. It’s also less likely to fall foul of development aspirations or infrastructure projects. The vicious cycle of degradation and neglect of small patches of habitat can be converted into a virtuous cycle when their value is communicated and local communities get behind preserving and managing them.
Urban planners and developers can get on board too. Rather than policies that enable the loss of vegetation in urban areas, we should be looking at restoring habitats in places that have lost or are losing them. This is key to designing healthy, liveable cities as well as protecting threatened species.
Biodiversity-sensitive urban design makes more of local vegetation by complementing the natural remnant patches with similar habitat features in the built environment, while delivering health and well-being benefits to residents. Urban development should be seen as an opportunity to enhance biodiversity through restoration, instead of an inevitable driver of species loss.
The conflict between urbanites and wildlife recently developed a new battleground: the small coastal New South Wales town of Batemans Bay, where the exceptional flowering of spotted gums has attracted a huge influx of grey-headed flying-foxes from across Australia’s southeast.
In response to intense and highly publicised community concern, federal Environment Minister Greg Hunt has announced he will seek an immediate National Interest Exemption to facilitate dispersal of these bats – a move that risks undermining legal protections afforded to this and other threatened species.
With the ongoing expansion of the human urban footprint, animals are increasingly confronted with urban environments. Human encroachment into natural habitats generally negatively affects biodiversity. However, urban landscapes can present wildlife with an irresistible lure of reliable food supplies and other resources. While urban wildlife can provide a range of benefits to health and wellbeing, it can also be cause for frustration and conflict.
Urban human-wildlife conflict is a growing area of management concern and scientific research. But the research suggests that the current strategies for addressing NSW’s conflicts between humans and flying-foxes might not have the intended results.
Ruling the urban roost
Australian flying-foxes are becoming more urbanised, and the noise, smell and droppings from their roosts can have huge impacts on local residents.
A fundamental problem underlying current approaches to urban roosts is a lack of understanding of the extraordinary mobility of flying-foxes. They are some of the most mobile animals in Australia, with movements that range from foraging trips of up to 120 km in a single night to long-distance nomadism covering thousands of kilometres in a single year.
While roosts can remain active for decades, they are more like backpacker hostels than stable households, housing a constantly changing clientele that comes to visit local attractions. Roosts are connected into large networks through which flying-foxes move in response to changes in local food resources.
This explains the sudden influx in places such as Batemans Bay where preferred food suddenly becomes abundant. But it also highlights the importance of a national approach to flying-fox management and conservation.
Intense local flowerings of Eucalypts, such as spotted gums, produce copious amounts of nectar and pollen, which attract large numbers of flying-foxes and other species for several weeks. When a relatively small local flying-fox population that is tolerated by its human neighbours suddenly increases tenfold, it can place severe pressure on the local community.
Despite their transient nature, these influxes are often wrongly interpreted as population explosions, leading to calls for culling. In comparison, more humane tactics – such as using loud noise or vegetation removal to disperse the flying-foxes – can seem like a more balanced response. But does dispersal actually work?
Shifting the problem elsewhere
There is now ample evidence to show that dispersals are extremely costly and can exacerbate the very human-wildlife conflict that they aim to resolve.
Most dispersals result in the flying-foxes returning the original roost as soon as the dispersal program ends, because naïve new individuals continue to arrive from elsewhere. Overcoming this can take months or years of repeated daily dispersal.
Other dispersals result in flying-foxes establishing new roosts a few hundred metres away, typically within the same urban environment in locations that we cannot control. This risks shifting the problem to previously unaffected members of a community and to other communities nearby.
While flying-foxes are often portrayed as noisy pests, they serve our economic interest by providing irreplaceable pollination and seed-dispersal services for free. What’s more, those same bats that annoy people during the day work tirelessly at night to maintain the health of our fragmented forests and natural ecosystems.
So it is in our national interest to manage conflict at urban roosts, by using approaches that balance community concerns with environmental considerations.
To be considered “successful”, a dispersal should permanently reduce conflict to a level that is acceptable to the community without causing significant harm to the animals. However, dispersals are currently implemented at the local council level with little or no monitoring of the impacts in or outside the immediately affected area. This makes it hard to assess whether they have been successful.
For example, it is not uncommon for flowering to cease and flying-fox numbers to decline naturally during the period of active dispersal. This gives the community a false sense that a permanent solution has been achieved, when in fact the issues will recur the next time the trees blossom. There is thus an urgent need for urban roosts to be managed with properly defined and applied criteria for success.
Unfortunately, lack of research effort directed at “ugly” and “less popular” Australian animals means that very few evidence-based management tools are available to deal with contentious roosts.
Research targeting a few key areas would greatly help efforts to improve urban roost management. For instance, we do not know how flying-foxes choose their roost sites, which leaves us unable to design “carrot solutions” by creating more attractive roost sites elsewhere.
Intensive tree-flowering events are relatively infrequent and hard to predict. This means that it is difficult to prepare communities for a sudden influx of flying-foxes.
Furthermore, the acceptability of various flying-fox management options differs between sections of the community, so it is difficult to find optimal solutions. Social scientists are currently trying to help identify priority areas that promote long-term viability of flying-foxes while also easing conflict with humans.
Local, state and federal governments continue to allocate considerable funds for dispersal responses, even though such actions are high-risk activities for local communities and are unlikely to provide long-term solutions. We argue strongly that targeted research is needed to better inform land managers and affected communities of flying-fox ecology and provide them with low-cost, low-risk, evidence-based tools for dealing with urban roosts.
Flying-foxes don’t care about legislative borders, and state-based responsibility for wildlife management leads to discontinuity in approaches between jurisdictions. While flying-foxes are being monitored at the national scale, this initiative needs to be combined with a uniform federal approach for managing flying-foxes in our human landscapes. Otherwise, conflicts such as those faced by the residents of Batemans Bay will continue unabated.
I recently wrote about how important it is to be able to identify plants and animals. Knowing the names of species that live around us helps us to connect to nature.
Yes, you can enjoy greenery and birdsong without knowing which species are involved, but recognising the call of a magpie while walking under a lemon-scented gum can enrich your experience. It makes nature more personal and accessible.
The most diverse and common group of animals in your neighbourhood (and mine) are the insects. Children are often drawn to these mini-beasts and are too often warned away by well-meaning adults who are afraid they might get stung.
The fact is that knowing your insects is a gateway to developing a relationship with the natural world. Who has not marvelled at a trail of ants carrying crumbs, enjoyed the sound of cicadas on a hot summer day, or watched bees pollinate flowers?
Insects are found everywhere and are incredibly diverse. They are critical to the health of any ecosystem, including your backyard or garden. Knowing enough to tell the main groups apart is a great way to learn about animals.
Insect swarm at my place
We had an interesting experience in our garden last week. Several wattle birds were swooping overhead and then half a dozen magpies arrived and started pecking at the grass at our feet. This was unusual behaviour so we watched closely and eventually noticed a swarm of insects above the vegetable patch.
There were both small and large insects in the swarm and I guessed that the large ones were predators, enjoying the feast along with the birds, but I was wrong. After finding the sweep net and collecting a few we realised that we were looking at a termite mating swarm. The larger insects were the females, and every now and then pairs dropped to the grass to do the deed.
Many people when they hear this story will cringe at the implications of having termites near the house, but most termite species do not eat wood and are not a danger to infrastructure. We placed a few dozen into a mesh enclosure along with some water, newspaper, wood and a jar of soil. The next day they had all burrowed into the soil, so we think they hatched out of our garden compost.
How did I know they were termites? Because termites belong to the order Isoptera, which literally means “same wings”. Unlike most insects, their four wings are all the same size and shape. Once you know this it is easy to distinguish between them and winged ants (who have four wings of different sizes) or flies (who have only two wings). A little bit of knowledge is a powerful thing.
Learning more about bugs
How will you learn to identify insects? A new book called Miniature Lives: identifying insects in your home and garden, by Michelle Gleeson would be a good start. It was mentioned on the CSIRO blog just a few days ago.
If you look around, you may find activities like Bring Ya Bug Along, which will be run by a friend of mine in our home town in a few weeks.
Of course, not every bug will be a bug. This sounds odd but there is an order of insects known as “true bugs” (Hemiptera). They have sucking mouthparts which they use to pierce plants or prey. So even the word “bug” has some linguistic problems and how you use it depends on who you are talking to.
Beetles are the most common insect order (Coleoptera), and most people can recognise them from the hard wing covers. Probably the most popular insect order is the Lepidoptera (moths and butterflies). Yes, they are beautiful but their caterpillars can be bad for the garden.
Lacewings (order Neuroptera) are also beautiful in their adult form. As juveniles they are called ant-lions, which are fearsome little predators that eat garden pests. You can even buy lacewings eggs from Bunnings to add to the garden.
I could go on but if I have sparked your interest, just buy a book or go online to start learning. Using insects as a gateway to connect with nature is something everyone can do.
When first looking at the pictures it is easy to think that the photos are fake or that they have been set up, but wildlife experts claim that the photos are genuine. The report first surfaced in The Cairns Post.
Golden Orb Weaver Spiders usually prey on large insects and not birds. It is unlikely that the spider would be able to consume the entire bird.