Plants use advertising-like strategies to attract bees with colour and scent

File 20180411 540 1wj58ue.jpg?ixlib=rb 1.1
A honeybee (left), a scarab beetle (middle), and a fly (right) feeding on flowers of the white rock rose in a Mediterranean scrubland.
Aphrodite Kantsa., Author provided

Aphrodite Kantsa, University of the Aegean and Adrian Dyer, RMIT University

Watching plants and pollinators such as bees can teach us a lot about how complex networks work in nature.

There are thousands of species of bees around the world, and they all share a common visual system: their eyes are sensitive to ultraviolet, blue and green wavelengths of the light spectrum.

This ancient colour visual system predates the evolution of flowers, and so flowers from around the world have typically evolved colourful blooms that are easily seen by bees.

For example, flowers as perceived by ultraviolet-sensitive visual systems look completely different than what humans can see.

However, we know that flowers also produce a variety of complex, captivating scents. So in complex natural environments, what signal should best enable a bee to find flowers: colour or scent?

Our latest research uncovered a surprising outcome. It seems that rather that trying to out-compete each other in colour and scent for bee attention, flowers may work together to attract pollinators en masse. It’s the sort of approach that also works in the world of advertising.

Read more:
Want a better camera? Just copy bees and their extra light-sensing eyes

Daunting amount of field work

Classic thinking would suggest that flowers of a particular species should have reasonably unique flower signatures. It makes sense that this should promote the capacity of a bee to constantly find the same rewarding species of flower, promoting efficient transfer of pollen.

So a competition view of flower evolution for different flower species with the same colour – for example purple – would suggest that each flowering plant species should benefit from having different scents to enable pollinator constancy and flower fidelity. By the same logic, flowers with the same scents should have different colours so they’re easily distinguished.

To know for sure what happens requires a daunting amount of field work. The challenges include measuring flower colours using a spectrophotometer (a very sensitive instrument that detects subtle colour differences) and also capturing live flower scent emissions with special pumps and chemical traps.

A wild bee of the genus Anthophora upon making the decision to visit the flowers of purple viper’s bugloss, in a Mediterranean scrubland in Greece.
Aphrodite Kantsa.

At the same time, in order to record the actual pollinator “clientele” of the flowers, detailed recordings of visits are required. These data are then built into models for bee perception. Statistical analyses allow us to understand the complex interactions that are present in a real world evolved system.

Not what we thought

And what we found was unexpected. In two new papers, published in Nature Ecology & Evolution and in Nature Communications, we found the opposite to competition happens: flowers have evolved signals that work together to facilitate visits by bees.

So flowers of different, completely unrelated species might “smell like purple”, whilst red coloured species share another scent. This is not what is expected at all by competition, so why in a highly evolved classical signal receiver has this happened?

The data suggests that flowers do better by attracting more pollinators to a set of reliable signals, rather than trying to use unique signals to maximise individual species.

By having reliable multimodal signals that act in concert to allow for easy finding of rewarding flowers, even of different species, more pollinators must be facilitated to transfer pollen between flowers of the same species.

Read more:
Which square is bigger? Honeybees see visual illusions like humans do

Lessons for advertising

A lot of research on advertising and marketing is concerned with consumer behaviour: how we make choices. What drives our decision-making when foraging in a complex environment?

While a lot of modern marketing emphasises product differentiation and competition to promote sales, our new research suggests that nature can favour facilitation. It appears that by sharing desirable characteristics, a system can be more efficient.

This facilitation mechanism is sometimes favoured by industry bodies, for example Australian avocados and Australian honey. En masse promotion of the desirable characteristics of similar products can grow supporter base and build sales. Our research suggests evolution has favoured this solution, which may hold important lessons for other complex market based systems.

A successful colour–scent combination targeted at attracting bees can be adopted by several different plant species in the same community, implying that natural ecosystems can function as a “buyers markets”.

Read more:
Curious Kids: Do bees ever accidentally sting other bees?

We also know from research that flowers can evolve and change colours to suit the local pollinators. Colours can thus be changed by flowers if instead of bees pollinating flowers, flies, with different colour perception and preferences, dominate the community.

These findings can also prove useful for identifying those colour-scent combinations that are the most influential for the community. This way, the restoration of damaged or disrupted plant-pollinator communities can become better managed to be more efficient in the future.

The ConversationWhen next enjoying a walk in a blooming meadow, remember plants’ strategies. The colourful flowers and the mesmerising scents you experience may have evolved to cleverly allure the efficient pollinators of the region.

Aphrodite Kantsa, Postdoctoral Researcher, University of the Aegean and Adrian Dyer, Associate Professor, RMIT University

This article was originally published on The Conversation. Read the original article.


Why we are measuring the health of Australian vegetation poorly

File 20180403 189801 8ff79t.jpg?ixlib=rb 1.1
The Victorian mountain ash forest has been severely affected by fires and logging. To determine the actual health of the forest, we need to look at the quality, not just the quantity of what remains.
Graeme/flickr, CC BY-NC

Ayesha Tulloch, University of Sydney; David Lindenmayer, Australian National University, and Hugh Possingham, The University of Queensland

Many of Australia’s ecosystems are in a much worse condition than we think. This is because officials are measuring the health of ecosystems such as forests and woodlands by their size, instead of how damaged they are by disturbances.

A “disturbance” is a short-term change in environmental conditions that leads to a long-term change in an ecosystem. Some habitat disturbances are natural, such as some fires and extreme weather events. Others are created by human activities, such as logging, pollution, intensive grazing, and mining.

Read more:
Native forest protections are deeply flawed, yet may be in place for another 20 years

Frequent or intense disturbances generally pose a bigger threat to the health of an ecosystem and it’s not limited to the area of the ecosystem that is lost. This is because the quality of the vegetation that survives a disturbance, such as a fire, may be too low to support the animals that rely on it for food and shelter.

It is much easier simply to measure ecosystem extent rather than ecosystem condition. However, focusing on quantity instead of quality leads to less informed decisions about where and how to conserve native habitats and the wildlife that lives in it.

Disturbances to habitats

Disturbances have grown in frequency and variety. This is one of the major causes of habitat degradation.

Fires are a common and dangerous disturbance to many Australian habitats. The number of bushfires per week in Australia increased by 40% between 2008 and 2013. Increases in the frequency of fires due to human activity have led to the decline or extinction of more than 100 species and declines in at least 29 threatened ecological communities listed in Australia’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

Burnt and unburnt mallee heath in southwest Australia.
Ashley Pearce/Angela Sanders

More attention is now being paid to evaluating the risk of our ecosystems going extinct. But most of the attention is only on the area of vegetation that has been lost, which is easy to map and calculate thanks to images from satellites.

Measuring the disturbances

In a recent study, we found that some Australian ecosystems are more threatened than might be suggested by looking simply at vegetation loss.

We made this discovery by assessing “whole-of-ecosystem degradation”. This calculation is a two-step process. First, we observe the different ages of the vegetation, known as their “age classes”, in an area. Then, we compare how far the current distribution falls short of the ideal distribution of the group of plants that make up that vegetation community.

Some species (such as large trees) require long intervals between disturbances to allow them to have time to mature and reproduce, so their “ideal” age class distribution will have many old plants and fewer young plants. Other species (such as some fast-growing shrubs) prefer short intervals between disturbances, and their ideal age class distribution will have more young plants than old plants.

The “whole-of-ecosystem degradation” approach

We used this approach to look at the dominant plants and animals in two vegetation types: the protea-rich mallee-heath of southwestern Australia, and Victoria’s mountain ash forest.

Banksias are a key component of the ecosystem in the protea-rich mallee-heath forest.

In the mallee-heath, the ideal distribution was based on the needs of Banksia species (which are in the Proteacea family). These plants provide critical nectar and pollen resources to many animals such as honey possums and honeyeaters. Many Banksias are long-lived and require up to 80 years between fires to maximise reproductive potential.

Our study showed that the banksia age-class distribution in this ecosystem is unbalanced, and therefore much poorer than indicated by information about just quantity. There are more young banksias (up to ten years old) and fewer older ones (more than 40 years old) than might otherwise be expected.

In simpler terms, the frequency of fire is clearly not able to support the flowering of banksia species, resulting in low habitat quality.

In the mountain ash (Eucalyptus regnans) forest, we used the food and shelter needs of the yellow-bellied glider (Petaurus australis) to assess forest health. This animal is already a threatened mammal.

Fire and logging have disturbed almost 50% of the forest in the last 30 years. Fires here are rare but of high intensity and severity, killing the trees in which these mammals live.

Again, our research shows that the remaining forest is in very poor condition. Compared to what would ideally be expected 120 years after a fire, the forest has more vegetation in very young (less than eight years old) and mid-age (up to 75 years old) age classes, and less vegetation in very old (more than 76 years old) age classes.

To sustain food sources and hollows for the yellow-bellied glider, the mountain ash would need to be protected from disturbance between 40 and 160 years.

The ideal time interval between fire disturbances to provide food and shelter to yellow-bellied gliders in mountain ash forest is more than 120 years, to allow new trees to grow after burning kills old trees. Photos show progression from newly burnt to old growth forest.
David Blair/Tabitha Boyer

Understanding the effect of disturbances

Our research shows that measuring an ecosystem’s health by its size alone can be misleading, especially when the area is large but severely degraded.

It is therefore crucial to consider disturbances when evaluating ecosystems. This is especially so when forest health is being assessed for listing through the IUCN Red List of Ecosystems, or for conservation planning and management.

Read more:
More sightings of an endangered species don’t always mean it’s recovering

We recommend that decision-makers be more aware of the role of disturbances in degrading ecosystems. This requires two crucial elements of information.

First, we need good maps that tell us when the last disturbance in an area was. This kind of mapping is carried out within our protected reserve system, but is not currently available at a national scale.

Second, we need a better understanding of ideal benchmarks of ecosystems to compare with the current conditions. Benchmarks may be linked to the needs of dominant plant species (such as banksia in mallee-heath) or the needs of dependent species of concern (such as yellow-bellied glider in mountain ash).

The ConversationWe propose that our method be applied to evaluate the condition of different ecosystems. This will ensure that ecosystem declines are identified before systems cannot be recovered.

Ayesha Tulloch, DECRA Research Fellow, University of Sydney; David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University, and Hugh Possingham, Professor, The University of Queensland

This article was originally published on The Conversation. Read the original article.

New research unlocks the mystery of leaf size

File 20170831 9971 75oye6
Leaf sizes vary according to a complex mix of temperature and water.
Peter Wilf/Supplied

Ian Wright, Macquarie University

Why is a banana leaf a million times bigger than a common heather leaf? Why are leaves generally much larger in tropical jungles than in temperate forests and deserts? The textbooks say it’s a balance between water availability and overheating.

But new research, published today in Science, has found it’s not that simple. Actually, in much of the world the key limiting factor for leaf size is night temperature and the risk of frost damage to leaves.

As a plant ecologist, I try to understand variation in plant traits (the physical, chemical and physiological properties of their tissues) and how this variation affects plant function in different ecosystems.

Read more: How we found out there are three trillion trees on Earth

For this study I worked with 16 colleagues from Australia, the UK, Canada, Argentina, the US, Estonia, Spain and China to analyse leaves from more than 7,600 species. We then teamed the data with new theory to create a model that can predict the maximum viable leaf size anywhere in the world, based on the dual risks of daytime overheating and night-time freezing.

These findings will be used to improve global vegetation models, which are used to predict how vegetation will change under climate change, and also to better understand past climates from leaf fossils.

Conifers, which grow in very cold climates, grow thin needles less vulnerable to frost.
Peter Reich

From giants to dwarfs

The world’s plant species vary enormously in the typical size of their leaves; from 1 square millimetre in desert species such as common eutaxia (Eutaxia microphylla), or in common heather (Calluna vulgaris) in Europe, to as much as 1 square metre in tropical species like Musa textilis, the Filipino banana tree.

But what is the physiological or ecological significance of all this variation in leaf size? How does it affect the way that plants “do business”, using leaves as protein-rich factories that trade water (transpiration) for carbon (photosynthesis), powered by energy from the sun?

More than a century ago, early plant ecologists such as Eugenius Warming argued that it was the high rainfall in the tropics that allowed large-leaved species to flourish there.

In the 1960s and ‘70s physicists and physiologists tackled the problem, showing that in mid-summer large leaves are more prone to overheating, requiring higher rates of “transpirational cooling” (a process akin to sweating) to avoid damage. This explained why many desert species have small leaves, and why species growing in cool, shaded understoreys (below the tree canopy) can have large leaves.

Rainforest plants under the tree canopy can grow huge, complex leaves.
Ian Wright

But still there were missing pieces to this puzzle. For example, the tropics are both wet and hot, and these theories predicted disadvantages for large-leafed species in hot regions. And, in any case, overheating must surely be unlikely for leaves in many cooler parts of the world.

Our research aimed to find these missing pieces. By collecting samples from all continents, climate zones and plant types, our team found simple “rules” that appear to apply to all of the world’s plant species – rules that were not apparent from previous, more limited analyses.

We found the key factors are day and night temperatures, rainfall and solar radiation (largely determined by distance from the Equator and the amount of cloud cover). The interaction of these factors means that in hot and sunny regions that are also very dry, most species have small leaves, but in hot or sunny regions that receive high rainfall, many species have large leaves. Finally, in very cold regions (e.g. at high elevation, or at high northern latitudes), most species have small leaves.

Understanding the mechanisms behind leaf size means leaf fossils – like these examples from the Eocene – can tell us more about climates in the past.
Peter Wilf/Supplied

But the most surprising results emerged from teaming the new theory for leaf size, leaf temperature and water use with the global data analyses, to investigate what sets the maximum size of leaves possible at any point on the globe.

This showed that over much of the world it is not summertime overheating that limits leaf sizes, but the risk of frost damage at night during cold months. To understand why, we needed to look at leaf boundary layers.

Every object has a boundary layer of still air (people included). This is why, when you’re cold, the hair on your arms sticks up: your body is trying to increase the insulating boundary of still air.

Larger leaves have thicker boundary layers, which means it is both harder for them to lose heat under hot conditions, and harder to absorb heat from their surroundings. This makes them vulnerable to cold nights, where heat is lost as long-wave radiation to the night-time sky.

So our research confirmed that in very hot and very dry regions the risk of daytime overheating seems to be the dominant control on leaf size. It demonstrated for the first time the broad importance of night-time chilling, a phenomenon previously thought important just in alpine regions.

Still, in the warm wet tropics, it seems there are no temperature-related limits to leaf size, provided enough water is available for transpirational cooling. In those cases other explanations need to be considered, such as the structural costs and benefits of displaying a given leaf area as a few large leaves versus many more, smaller leaves.

The view from a canopy crane at the Daintree in Queensland.
Peter Wilf

These findings have implications in several fields. Leaf temperature and water use play a key role in photosynthesis, the most fundamental plant physiological function. This knowledge has the potential to enrich “next-generation” vegetation models that are being used to predict regional-global shifts in plant nutrient, water and carbon use under climate change scenarios.

These models will aid the reconstruction of past climates from leaf macrofossils, and improve the ability of land managers and policymakers to predict the impact of a changing climate on the range limits to native plants, weeds and crops.

The ConversationBut our work is not done. Vegetation models still struggle to cope with and explain biodiversity. A key missing factor could be soil fertility, which varies both in space and time. Next, our team will work to incorporate interactions between soil properties and climate in their models.

Ian Wright, Associate Professor in the Department of Biological Sciences, Macquarie University

This article was originally published on The Conversation. Read the original article.

Rising carbon dioxide is making the world’s plants more water-wise

Pep Canadell, CSIRO; Francis Chiew, CSIRO; Lei Cheng, CSIRO; Lu Zhang, CSIRO, and Yingping Wang, CSIRO

Land plants are absorbing 17% more carbon dioxide from the atmosphere now than 30 years ago, our research published today shows. Equally extraordinarily, our study also shows that the vegetation is hardly using any extra water to do it, suggesting that global change is causing the world’s plants to grow in a more water-efficient way.

Water is the most precious resource needed for plants to grow, and our research suggests that vegetation is becoming much better at using it in a world in which CO₂ levels continue to rise.

The ratio of carbon uptake to water loss by ecosystems is what we call “water use efficiency”, and it is one of the most important variables when studying these ecosystems.

Our confirmation of a global trend of increasing water use efficiency is a rare piece of good news when it comes to the consequences of global environmental change. It will strengthen plants’ vital role as global carbon sinks, improve food production, and might boost water availability for the well-being of society and the natural world.

Yet more efficient water use by the world’s plants will not solve our current or future water scarcity problems.

Changes in global terrestrial uptake of carbon dioxide, water use efficiency and ecosystem evapotranspiration during 1982-2011.

Boosting carbon uptake

Plants growing in today’s higher-CO₂ conditions can take up more carbon – the so-called CO₂ fertilisation effect. This is the main reason why the terrestrial biosphere has taken up 17% more carbon over the past 30 years.

The enhanced carbon uptake is consistent with the global greening trend observed by satellites, and the growing global land carbon sink which removes about one-third of all CO₂ emissions generated by human activities.

Increasing carbon uptake typically comes at a cost. To let CO₂ in, plants have to open up pores called stomata in their leaves, which in turn allows water to sneak out. Plants thus need to strike a balance between taking up carbon to build new leaves, stems and roots, while minimising water loss in the process. This has led to sophisticated adaptations that has allowed many plant species to conquer a range of arid environments.

One such adaptation is to close the stomata slightly to allow CO₂ to enter with less water getting out. Under increasing atmospheric CO₂, the overall result is that CO₂ uptake increases while water consumption does not. This is exactly what we have found on a global scale in our new study. In fact, we found that rising CO₂ levels are causing the world’s plants to become more water-wise, almost everywhere, whether in dry places or wet ones.

Growth hotspots

We used a combination of plot-scale water flux and atmospheric measurements, and satellite observations of leaf properties, to develop and test a new water use efficiency model. The model enables us to scale up from leaf water use efficiency anywhere in the world to the entire globe.

We found that across the globe, boreal and tropical forests are particularly good at increasing ecosystem water use efficiency and uptake of CO₂. That is due in large part to the CO₂ fertilisation effect and the increase in the total amount of leaf surface area.

Importantly, both types of forests are critical in limiting the rise in atmospheric CO₂ levels. Intact tropical forest removes more atmospheric CO₂ than any other type of forest, and the boreal forests of the planet’s far north hold vast amounts of carbon particularly in their organic soils.

Meanwhile, for the semi-arid ecosystems of the world, increased water savings are a big deal. We found that Australian ecosystems, for example, are increasing their carbon uptake, especially in the northern savannas. This trend may not have been possible without an increase in ecosystem water use efficiency.

Previous studies have also shown how increased water efficiency is greening semi-arid regions and may have contributed to an increase in carbon capture in semi-arid ecosystems in Australia, Africa and South America.

Trends in water use efficiency over 1982-2011.
CREDIT, Author provided

It’s not all good news

These trends will have largely positive outcomes for the plants and the animals (and humans) consuming them. Wood production, bioenergy and crop growth are (and will be) less water-intensive under climate change than they would be without increased vegetation water use efficiency.

But despite these trends, water scarcity will nevertheless continue to constrain carbon sinks, food production and socioeconomic development.

Some studies have suggested that the water savings could also lead to increased runoff and therefore excess water availability. For dry Australia, however, more than half (64%) of the rainfall returning to the atmosphere does not go through vegetation, but through direct soil evaporation. This reduces the potential benefit from increased vegetation water use efficiency and the possibility for more water flowing to rivers and reservoirs. In fact, a recent study shows that while semi-arid regions in Australia are greening, they are also consuming more water, causing river flows to fall by 24-28%.

The ConversationOur research confirms that plants all over the world are likely to benefit from these increased water savings. However, the question of whether this will translate to more water availability for conservation or for human consumption is much less clear, and will probably vary widely from region to region.

Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO; Francis Chiew, Senior Principal Research Scientist, CSIRO; Lei Cheng, Postdoctoral research fellow, CSIRO; Lu Zhang, Senior Principal Research Scientist, CSIRO, and Yingping Wang, Chief research scientist, CSIRO

This article was originally published on The Conversation. Read the original article.

Land clearing isn’t just about trees – it’s an animal welfare issue too

File 20170704 10704 10o5p14
This quenda seems to have been a victim of land clearing.
Colin Leonhardt/, Author provided

Hugh Finn, Curtin University

Tens of millions of wild animals are killed each year by land clearing across Australia, according to our research on the harm done to animals when native vegetation is removed for agricultural, urban and industrial development.

As my colleague Nahiid Stephens and I point out in our study, this harm to animals is largely invisible, unlike the obvious effects of clearing on trees and other plants. But just because something is invisible, that does not mean it should be ignored.

We argue that reforms are necessary to ensure that decision-makers take wild animals’ welfare into account when assessing development proposals and land clearing applications.

How does land clearing harm animals?

Land clearing harms animals in two basic ways. First, they may be killed or injured when native vegetation is removed, typically through the use of earth-moving machinery. For example, animals may suffer traumatic injuries or be smothered when vegetation is cut or soil and debris are shifted.

Second, the removal of native vegetation puts animals in harm’s way. Those that survive the clearing process will be left in an environment that is typically hostile, unfamiliar or unsuitable. Animals are likely to find themselves in landscapes that are devoid of food and shelter but filled with predators, disease, and increased aggression from members of their own species as they struggle to make a living.

Land clearing causes animals to die in ways that are physically painful and psychologically distressing. Animals will also suffer physical injuries and other pathological conditions that may persist for days or months as they try to survive in cleared areas or other environments to which they are displaced.

Many reptiles and mammals are territorial or have small home ranges, and thus have strong associations with small areas of habitat. Koalas in urban areas, for example, tend to rely on particular food trees. Likewise, lizards and snakes often rely on particular microhabitat features such as logs, rocks, and leaf litter to provide the combination of temperature and humidity that they need to survive.

Laws are not protecting animals

Land clearing remains a fundamental pressure on the Australian environment. While the regulatory frameworks for land clearing vary greatly across the Australian states and territories, the principal statutes that govern native vegetation clearance in most jurisdictions typically contain some sort of express recognition of the harm that land clearing causes, such as the loss or fragmentation of habitat, land degradation, and salinity.

Habitat lost: land cleared for the now-discontinued Perth Freight Link road project.
Colin Leonhardt/, Author provided

Yet these regulations are uniformly silent on the issue of how land clearing harms animals. No state or territory has developed a clear framework to evaluate this harm, let alone minimise it in future development proposals.

This failure to recognise animal welfare as a significant issue for decision-making about land clearing is troubling, especially given the scale of current land clearing. In Queensland, for example, an estimated 296,000 hectares of woody vegetation was cleared in 2014-15, nearly all of which was for the purpose of converting native vegetation to pasture. In our study we estimate that, on the basis of previous studies and current estimates of clearing rates, land clearing in Queensland and New South Wales combined kills more than 50 million birds, mammals and reptiles each year.

What reforms are necessary?

We suggest that two basic reforms are required. First, state and territory parliaments should amend the laws that govern environmental impact assessments and native vegetation clearance, to require decision-makers to take animal welfare into account when assessing land clearing applications.

Second, we urgently need accurate ways to evaluate the harm that proposed clearing actions may cause to individual animals. Animal welfare is broadly recognised as an important social concern, so it makes sense that in a situation where we know animals are being harmed, we should take steps to measure and prevent that harm.

The basic aim of any reform should be to ensure that the harm that land clearing causes to individual wild animals is appropriately considered in all forms of environmental decision-making and that such evaluations are based on clear and objective criteria for animal welfare.

At a minimum, those who apply to clear native vegetation should be required to provide an estimate of the number and type of native animals that will be killed by the proposed land clearing. This would ensure that all parties – applicants, decision-makers, and the community – understand the harm that the clearing would cause. These estimates could be made by using population density information for species that are likely to be affected – an approach that has been already been used.

We also need to revise our perceptions about the usefulness and necessity of land clearing in Australia. A better idea of what is “acceptable” would include not only the environmental costs of clearing an area of native vegetation, but also the individual suffering that animals will experience.

Issues of causation and responsibility are critical here. While it’s unlikely that someone who wants to clear land actually wants native animals to suffer, such suffering will nevertheless be an inevitable consequence. The relevant question is not whether animals will be killed and harmed when land is cleared, but how much of that harm will occur, how severe it will be, and whether it ought to be avoided.

The ConversationIf such harm is deemed necessary – based on an accepted system for weighing the potential benefits and harms – the next question is how the harm to animals can be minimised by, for example, keeping the amount of vegetation to be cleared to a minimum.

Hugh Finn, Lecturer, Curtin University

This article was originally published on The Conversation. Read the original article.

How Australia’s animals and plants are changing to keep up with the climate

Image 20170315 11555 cknzgv
Flora and fauna can adapt to climate change, but some are more successful than others.

Ary Hoffmann, University of Melbourne

Climate change is one of the greatest threats facing Australia’s wildlife, plants and ecosystems, a point driven home by two consecutive years of mass coral bleaching on the Great Barrier Reef. The Conversation

Yet among this growing destruction there is a degree of resilience to climate change, as Australian animals and plants evolve and adapt.

Some of this resilience is genetic, at the DNA level. Natural selection favours forms of genes that help organisms withstand hotter and drier conditions more effectively.

Over time, the environmental selection for certain forms of genes over others leads to genetic changes. These genetic changes can be complex, involving many genes interacting together, but they are sufficient to make organisms highly tolerant to extreme conditions.

Some of this resilience is unrelated to DNA. These are “plastic” changes – temporary changes in organisms’ physical and biochemical functions that help them deal with adverse conditions or shifts in the timing of environmental events.

Plastic changes occur more quickly than genetic changes but are not permanent – the organisms return to their previous state once the environment shifts back. These changes also may not be enough to protect organisms from even more extreme climates.

What about Australia?

In Australia there is evidence of both genetic and plastic adaptation.

Some of the first evidence of genetic adaptation under climate change have been in vinegar flies on the east coast of Australia. These flies have a gene that encodes the enzyme alcohol dehydrogenase. This gene has two major forms: the tropical form and the temperate form. Over the past 30 years, the tropical form of the gene has become more common at the expense of the temperate one.

Plastic adaptation due to climate change has been demonstrated in common brown butterflies in southern Australia. Female butterflies are emerging from their cocoons earlier as higher temperatures have been speeding up their growth and development by 1.6 days every decade. According to overseas research, this faster development allows butterfly caterpillars to take advantage of earlier plant growth.

Higher temperatures are causing the common brown butterflies in southern Australia to come out of their cocoons earlier.
John Tann/Wikimedia Commons, CC BY-SA

In many cases, it is not clear if the adaptation is genetic or plastic.

The average body size of Australian birds has changed over the the past 100 years. Usually, when comparing birds of the same species, birds from the tropics are smaller than those from temperate areas. In several widespread species, however, the birds from temperate areas have recently become smaller. This might be the direct result of environmental changes or a consequence of natural selection on the genes that affect size.

In the case of long-lived species like eucalypts, it is hard to see any adaptive changes. However, there is evidence from experimental plots that eucalypts have the potential to adapt.

Different eucalypt species from across Australia were planted together in experimental forestry plots located in various environments. These plots have unwittingly become climate change adaptation experiments. By monitoring the plots, we can identify species that are better at growing and surviving in extreme climatic conditions.

Plot results together with other forms of DNA-based evidence indicate that some trees unexpectedly grow and survive much better, and are therefore likely to survive into the future.

What’s next?

We still have much to learn about the resilience of our flora and fauna.

There will always be species with low resilience or slow adaptive ability. Nevertheless, plastic and genetic changes can provide some resilience, which will change the predictions of likely losses in biodiversity.

Much like how our worst weeds and pests adapted to local climate conditions, as demonstrated many years ago, our local plants and animals will also adapt.

Species with short generation times – a short time between one generation (the parent) and the next (the offspring) – are able to adapt more quickly than species with longer lifespans and generation times.

For species with short generation times, recent models suggest that the ability to adapt may help reduce the impacts of climate change and decrease local extinction rates.

However, species with long generation times and species that cannot easily move to more habitable environments continue to have a high risk of extinction under climate change.

In those cases, management strategies, such as increasing the prevalence of gene forms helpful for surviving extreme conditions and moving species to locations to which they are better adapted, can help species survive.

Unfortunately, this means doing more than simply protecting nature, the hallmark of our biodiversity strategy to date. We need to act quickly to help our animals and plants adapt and survive.

Ary Hoffmann, Professor, School of BioSciences and Bio21 Institute, University of Melbourne

This article was originally published on The Conversation. Read the original article.