It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, August 22, 2023
Why beaver-like dams can protect communities from flooding
by Catherine Wilson, Elizabeth Follett, and Valentine Muhawenimana, The Conversation
A beaver-like dam at Wilde Brook on the Corve catchment in Shropshire. Credit: Daniel Jones, Author provided
Low cost, human-made river barriers, similar to those built by beavers, can protect communities at risk of flooding.Our new research has found that such natural barriers intentionally increase water levels upstream to slow down river flow.
These flood barriers are made of materials like logs, branches, mud and leaves. They reduce downstream water levels by deliberately blocking the river and storing the water. They then slow down the river flow during a storm.
Using natural processes to temporarily store water above and below ground is called natural flood management. It essentially involves using nature as a sponge to soak up rainwater.
Not only does this protect communities further down the river from flooding, but it has other benefits too. It helps to enhance habitat diversity for river insects and animals, trap pollutants, and enhance the supply of sediment to the floodplain.
It also adds resilience to the river during spells of dry and hot weather by preventing it from drying up entirely. That was a big issue during the summer of 2022, which was the UK's warmest on record.
Until our recent research, very little data existed on how effective such river barriers are, or how such approaches might best be used. We also did not understand how these beaver-like dams operate during big storms.
Slowing the flow
The presence of a tree trunk or similar obstacle in a river will disrupt its flow. But the exact extent to which the water flow was slowed down by one natural barrier, let alone 50 to 100 barriers, was unknown. We also did not understand how the flow changed for different types of storms and different river settings.
The theoretical idea of a natural barrier is that they have a big hole at the bottom for everyday river flows, as well as holes in between the logs and branches in the upper part of the barrier where the water slowly flows through after a small storm.
During heavy rainfall, the water level gets higher and flows over the top of the barrier.
Beavers are natural engineers and make dams by using their teeth to cut trees and branches. Credit: Mark A. Rice/Shutterstock
We found that the barrier's holes can become bigger due to the changing flow of the river. In addition, during a storm, the twigs, leaves and sediment transported by the river flow can accumulate behind the barrier, causing it to grow in size. So, we needed to understand how these natural barriers evolve over time to understand the range of their effectiveness.
Engineers use computer models called "flood models" which use mathematical equations to predict how different storm sizes impact on river water levels. These help us predict when a river will burst its banks, and then the location and extent of a flooded area.
This is important as it helps governments decide on what type of flood defense is needed to protect people from existing and future flooding. It also helps to determine where new buildings can be constructed that will be safe from flooding, and that such new builds will not make existing houses more vulnerable to floods.
The Corve catchment in Shropshire
We gathered data from 105 natural flood barriers on a small Shropshire river to measure their effectiveness in holding back flood waters and to understand how natural flood barriers operate during a storm. We collected water levels, velocity and flow data every 15 minutes for a two year period.
We also used a technique called "photogrammetry". This is where data from drone photographs are used to obtain accurate measurements of the topography in areas of river covered by trees and other vegetation.
Our results showed that the natural flood barriers at the site could store enough water to fill at least four Olympic-sized swimming pools during significant storms such as Storm Dennis, which hit the UK in February 2020.
This shows that natural barriers are effective in slowing down the flow of the river during periods of rainfall, storing up vast quantities of water which would otherwise rush through, causing damage to areas downstream. Instead, this force is slowly released over a period of one to two weeks.
Our research shows that natural flood management works. It is also cheaper than traditional engineering works and complements rather than replaces existing flood defenses.
The information from our study will help natural barriers be more accurately represented in flood models, using our new observations on barrier changes over time and effectiveness during storms.
Society can get better value from our flood defense spending by supporting landowners to install natural solutions. This is increasingly an issue as more and more houses are being built on land at risk of flooding.
Seine pollution forces cancelation of third Olympics test event
by Clément VARANGES
The starting line for the 2023 World Triathlon pre-Olympics test event floating on the Seine River in Paris.
The swimming stage of a triathlon in Paris's Seine River was canceled on Sunday due to pollution, organizers announced, raising further questions about holding competitions there during the 2024 Olympics.
The mixed relay triathlon is the third pre-Olympics test event to be affected by excessive E. coli bacteria in the water, but organizers insist the Seine will be fit to host events next year.
The triathlon was changed to a duathlon only involving cycling and running after analyzes of the water quality did not offer the "necessary guarantees," said the Paris Olympics organizing committee and governing body World Triathlon.
The same solution was reached for a para-triathlon test event on Saturday, while the World Aquatics Open Water Swimming World Cup was canceled altogether earlier this month.
As organizers investigated the source of Saturday's elevated E. coli readings Tony Estanguet, the head of the Paris 2024 organizing committee, stressed there was no "Plan B" for next year's sporting extravaganza.
"There is no solution to move the event, the triathlon and open water swimming will be held in the Seine next year," he insisted.
"From the start, we have remained on the same project, to organize the triathlon and para-triathlon in this extraordinary site. You have a beautiful setting between the Grand Palais, the Invalides, this Alexandre III bridge. This course, I believe, is unanimous."
The cause of this impasse in the Seine remains the same: the concentration of Escherichia Coli (E. coli) bacteria in the river.
Storms, causing heavy rainfall leading to overflowing sewers spilling into the river, are not the cause, officials insist.
"An investigation is underway to find the cause of this degradation but, to date, we have not yet found an explanation," Pierre Rabadan, deputy mayor of Paris in charge of Sport and the Olympics told AFP.
"We missed out by very little," said French sports minister Amelie Oudea-Castera.
"It's extremely encouraging, you have to see the glass half full. I repeat, we will be ready."
Athletes dive into the Seine River on Friday for the men's 2023 World Triathlon pre-Olympic test event.
"Still being developed'
A triathlon has never been converted into a duathlon at the Olympics since its introduction at the 2000 Sydney Games.
"It would be a shame but we adapted to a duathlon this morning," said Beth Potter, winner of the women's race on Thursday and second in Sunday's mixed relay with the British team.
"Hopefully by next year it will be okay. We saw that for the individual races it was okay, so hopefully it will be a triathlon."
Britain's Alex Yee, winner of the men's race, added, "They are saying the water filtering is still being developed. So by next year it will be perfect.
"What they are doing is hugely historic, they are leaving a legacy after the Games. We can only applaud them."
Local authorities are working to correct some 23,000 poor connections in private homes whose wastewater ends up in the river.
"We are a quarter of the way there," said Oudea-Castera.
French world champion Leo Bergere said he had not "heard that athletes had come out sick" from the men's race on Friday, the day on which the first below standard samples were taken.
"The objective was to make the Seine swimmable in 2024," added Estanguet.
"This test comes along the way, the plan has not reached maturity. There are still great efforts, new means being deployed to improve the quality of the water in the Seine. As we have seen, it is improving month by month and will continue to improve."
Olympic open water swimming has frequently been hit by pollution concerns.
At the end of the test event in 2019 ahead of the Tokyo Olympics, swimmers protested against the quality of the water in Tokyo Bay.
At the Rio Olympics in 2016, the prospect of swimming in the polluted Guanabara Bay also made headlines.
The clamour for coups among citizens is rising. Credit: Wikimedia Commons
On the night of 13 January 1963, Togo's President Sylvanus Olympio was shot dead by rebels in the first military coup staged in Africa. A long list, as shown below, was to come. From the 1960s to the end of the millennium, there were an average of four military coups a year on the continent. By the end of the 1990s this phenomenon seemed to have faded away.
But since August 2020 six African nations have suffered seven coups or attempted coups.
First came Mali, in August 2020. The military took advantage of social unrest and insecurity caused by the activities of violent extremists. Mali had two coups or attempts in a nine-month span.
In April 2021, Chad followed the same path. In March 2021, there was a coup attempt in Niger, and in September 2021 it was Guinea's turn. A month later, it was Sudan. In Burkina Faso, an attack in November 2021 led to the coup in January 2022.
More recently, a coup was launched in Niger, deposing President Mohamed Bazoum. Two days later, General Abdourahamane Tchiani declared himself the leader of Niger.
All together, that's more than 100 million people being ruled by the military after power was seized violently. All are in the Sahel. This has alerted governments in the region.
Researchers, analysts and journalists have pointed to mismanagement, incompetence, corruption, economic crisis and state weakness as the main factors propelling military coups all over the world and, of course, in Africa. State weakness is a factor in the recent instances in Africa. They have happened partly because of governments' failure to stem the spread of groups linked to Al Qaeda and the Islamic State all over the Sahel.
But there are two intertwined characteristics that differentiate Africa from the rest of the world. One is the public support of many citizens on the streets when there is a coup. The other is the society's rising support for military rule as a form of government. Popular support for military rule has grown in the last 20 years.
My research explored the reasons for this. I used survey data to examine whether support for nondemocratic rule was mainly due to poor institutional and economic performance or to an existing so-called authoritarian personality and culture in the region. This type of personality refers to values existing in certain societies that make them more prone to embrace authoritarian forms of government.
This distinction is relevant because if the reason for military rule support is cultural, then societies will continue to endorse authoritarian regimes. If the reason is institutional performance, then as long as incumbent governments perform efficiently, both politically and economically, democratic support will overcome authoritarian support.
Citizen discontent
I carried out a quantitative analysis using Afrobarometer survey data gathered from 37 African countries, both from North Africa and Sub-Saharan Africa. The analysis looked for underlying factors propelling the rise in support for military rule.
Respondents were asked about the extent of their support for military rule as a form of government plus a number of other potential explanatory questions such as perception of corruption, governing and opposition parties performance, economy evaluation and socio-demographic issues like their level of education.
The data shows that from 2000 to the present, the level of support for military rule as a form of government has doubled, from 11.6% of people supporting "much" or "very much" military rule as a form of government to 22.3%. Of the 37 countries analyzed, there were 11 where support for military dictatorship was decreasing and 26 where this figure was on the rise. The latest Afrobarometer data shows that support for democracy has fallen in the last year. Out of 38 countries, only four show decreasing support for military rule since 2000, whereas 34 show higher support for higher military rule than in 2000.
Support for military rule was higher in "partly free" and "not free" countries than in "free" countries. (They were categorized according to the Freedom House index.)
But there were some exceptions. In South Africa, which is a constitutional democracy with regular elections, one in three South Africans supported military rule as a form of government. In democratic Namibia the level of support showed that one in four Namibians supported military rule.
Reasons to support military rule
The analysis points to three conclusions:
In sub-Saharan Africa, the legitimacy of military rule is mainly based on institutional performance and economic management. These are weakened by jihadist organizations rapidly expanding throughout the region. State institutions are not able to tackle their expansion throughout the region.
In North Africa, institutional performance plays a role but authoritarian personality plays a larger role in the support for military rule.
Education seems to be an antidote against authoritarianism. Those with higher level of education, according to survey data, show higher level of democratic endorsement.
The study's findings suggest that people in sub-Saharan Africa are fed up with their governments for many reasons, including security threats, humanitarian disasters and lack of prospects. Waiting for the next elections to take place to change government does not seem to them to be a good option. Opposition parties do not seem to enjoy a better image. For the survey respondents, the solution appears to be to welcome the military to intervene.
If citizens perceive that politicians don't care about them, this will invite the military to continue overthrowing civil governments, with society publicly legitimizing their intervention in politics.
If military, political and economic solutions are not found, military coups in the region will increase and people will continue gathering on the streets to welcome them. Niger's recent coup may not be the last one.
Local richness responses of ants and invertebrate communities to non-native ants. The number of studies for each taxon is in parentheses by taxon labels. Solid dots with black bars represent the overall standardized mean difference (Hedges' g) and 95% confidence intervals, respectively. Translucent circles represent individual taxon responses. The size of each circle is proportional to its relative weighting in the overall model and the inverse of its variance. A positive effect size means that invasive ants are reducing taxon richness. The position on the y-axis ("intercept") ensures that points are visible and do not overlap and is also determined by the taxonomic grouping variable. Several studies with very high effect sizes (>5) and taxa with fewer than five studies were omitted from the plot to aid visualization of the remaining data. Credit: Insect Conservation and Diversity (2023). DOI: 10.1111/icad.12672
New research by Cardiff University has measured the impact of ant invasions on native species at a global scale for the first time, finding that the introduction of invasive ants into new environments can reduce species numbers by 53% through competition and predation.
Ants play an important role in helping to maintain stable ecosystems, but some species of ants have been transported by humans globally and can cause major problems, even contributing to the extinction of some animal species.
The introduction of invasive ant species into habitats around the world through human activities, such as international commerce, has led to non-native ants establishing colonies in various habitats worldwide. Most research studying these populations show that invasive ants can lower native species diversity, probably through predation and competition.
Invasive ants possess adaptations that allow them to dominate most native ant species. This includes being able to eat a wide and general diet, as well as forming supercolonies—interconnected nests consisting of multiple queens and that can spread over large areas.
Dr. Maximillian Tercel, Cardiff University's School of Biosciences, said, "Ants are ecologically important social insects, helping to maintain key ecosystem functions. They participate in a wide range of species interactions, such as acting as predators, parasites, herbivores, granivores, prey, mutualists and hosts, across almost all terrestrial environments and all continents except Antarctica.
"But this means, through human transportation around the world, we have introduced different non-native species of ants into new areas—this can cause a lot of problems for the ecosystems and biodiversity in that area. Invasive ants are generally expected to lower native species diversity by predation and competition.
"However, case studies show that the effect of invasive ants might vary depending on where they invade and between different groups of animals. For example, birds might react badly to invasive ants but mammals or some insect groups may not react as badly—but this hasn't been measured until now.
"Ant invasions appear to be a really important element to consider when trying to conserve native biodiversity in many areas around the world, so we aimed to estimate the effect of invasive ants on animal community biodiversity for the first time."
The researchers extracted data from 46 published articles investigating the responses of animals to ant invasion in areas relatively unimpacted by other stressors, such as human disturbance. They focused on the impacts on the abundance and richness of species in those locations after ant invasions.
The Cardiff scientists calculated that an ant invasion reduces the total number of animal individuals in that location by 42% and reduces the number of species by 53% on average.
"This is a huge reduction in the diversity of animal communities and suggests that invasive ants can pose serious problems for the health of ecosystems in which they invade.
"These findings show that we urgently need to improve international prevention processes, early detection systems, and well-designed control strategies for invasive ants," added Dr. Tercel.
The research, "Non-native ants drive dramatic declines in animal community diversity: A meta-analysis," was published in Insect Conservation and Diversity.
More information: Maximillian P. T. G. Tercel et al, Non‐native ants drive dramatic declines in animal community diversity: A meta‐analysis, Insect Conservation and Diversity (2023). DOI: 10.1111/icad.12672
An aid to ecological management and ecosystem services supply and demand dynamics
by Maximum Academic Press
Location of TLB in the Yangtze River Delta in China. Credit: Circular Agricultural Systems
Ecosystem services (ESs) provide a variety of services and benefits for human well-being, but the supply-demand mechanism of ecosystem services under different spatio-temporal scales is unclear.
The Taihu Lake Basin (TLB) is a microcosm of degraded and unsustainable ecosystem services. Rapid industrialization and urbanization poses a great threat to the environment and ecology. Therefore, it is urgent to assess the changes in supply and demand for TLB ecosystem services from a spatio-temporal and multi-stakeholder perspective, and this will be conducive to the scientific and sustainable development of ecological services.
Circular Agricultural Systems published an online paper, entitled "Quantifying the difference between supply and demand of ecosystem services at different spatial-temporal scales: A case study of the Taihu Lake Basin," on 31 May 2023.
In this study, the InVEST model was used to quantify the dynamics of ESs supply and demand in the TLB from 2010–2020, and compared the mismatch between supply and demand for five ESs (i.e., water yield, carbon sequestration, recreation, food production, and heat regulation services) at four spatial scales (pixel scale, township scale, county scale, and city scale).
The study highlights the increasing quantitative and spatial differences in the supply and demand of environmental services in the TLB, in particular the conflict between carbon sequestration services and heat regulation services, which has become a major constraint to the development of environmental services.
However, there is a demand gap for water yield services and food production services. Evaluations of ecosystem service deficit and redundancy (ESDR) indicate that significant deficits are mainly in densely populated towns of the eastern and central regions, while high surplus areas are mainly in the forested areas in the southwest.
Comprehensive ecosystem service deficit and redundancy (CESDR) metrics showed a decline from -0.03 in 2010 to -0.05 in 2020, among which urban areas like Shanghai and Suzhou reflect pronounced imbalances. The data underscores the urgency for focused policy interventions in regions with high deficit.
In conclusion, this study analyzes the quantitative characteristics and spatial-temporal pattern of the relationship between the supply and demand of ESs in TLB at different scales. It emphasizes that a multi-scale analytical approach should be adopted in policy formulation to achieve a balance between supply and demand through reasonable ecological protection and ecological restoration.
More information: Wei Yang et al, Quantifying the difference between supply and demand of ecosystem services at different spatial-temporal scales: A case study of the Taihu Lake Basin, Circular Agricultural Systems (2023). DOI: 10.48130/CAS-2023-0005
A man jogs along the docks at sunrise to avoid the heat, in Bordeaux, southwestern France.
Millions of people in France sweated through a late summer heat wave on Monday, with record temperatures expected in the wine-growing Rhone valley region and a forest fire blazing in the southeast.
Temperatures are expected to peak on Tuesday and Wednesday, with the most intense heat in the southern parts of the country where the mercury is already pushing past 40 degrees Celsius (104 Fahrenheit).
Health authorities have placed roughly half of the 96 departments in mainland France on the second-highest heat warning level, with some areas around the Rhone set to be placed in the maximum red category on Tuesday.
"Some records could be broken, notably on Tuesday in the Rhone valley with 40-42°C expected," national weather service Meteo France said.
The heat wave is "intense and long-lasting" and "particularly late in the season", it added, with a period of high pressure creating a "heat dome" over the country.
After a suffocating summer of record temperatures and forest fires in 2022, France had for the most part experienced a typical holiday period this year, escaping the intense heat that scorched southern Europe in July.
The current highs are the hottest of the season, Meteo France said.
Many people headed to municipal swimming pools, fountains or the beach to cool off.
"We went to the pool, so it was a cheap and easy way to fight the heat," Nathalie Chopin told AFP in the southeastern city of Lyon.
"It's very hot. Otherwise, we stay in our apartments, close the shutters and shut ourselves in."
Fire fears
After several weeks of dry weather, local authorities in the southern Gard area of France restricted access to forests due to the high risks of fires.
Around 260 firefighters were battling a wildfire near the village of Chanousse in the foothills of the Alps in southeast France, according to the Association for the Prevention and Reporting of Forest Fires.
It has consumed around 120 hectares (nearly 250 acres) of woodland, according to local authorities.
The high temperatures have also interfered with the scheduled re-starting of a nuclear power plant in Golfech in southwest France and could also lead to restrictions at a plant in Bugey in the Ain area, power group EDF said.
Heat waves frequently affect France's river-side nuclear power plants which suck in river water for cooling purposes before discharging it downstream.
They are forced to reduce their water usage during hot spells to guard against excessive warming of rivers which could affect local ecosystems.
The highest temperature ever recorded in France was 46C, registered in June 2018 in the village of Verargues in southern France.
Temperatures reached 35C in Bordeaux on Monday afternoon, while 37C was recorded in Lyon, Perpignan and Toulouse.
The upcoming bushfire season in Australia may be bad, but future years pose a more significant threat, says a University of New South Wales bushfire expert.
The recent devastation caused by wildfires across Europe and Hawaii has sparked concerns about the return of catastrophic bushfires in Australia. Coupled with the forecast that the southern hemisphere is likely entering a hot and dry El Niño event, conditions could be favorable for major fires after a few years of subdued activity.
But Professor Jason Sharples, an expert in bushfires dynamics from UNSW Canberra, says while it's always hard to predict exactly what will unfold in Australia, it's unlikely to be a repeat of the 2019–2020 Black Summer bushfires.
"El Niño conditions don't necessarily mean we will have a worse bushfireseason, though it does mean we're more likely to have hotter temperatures, less rainfall, and dry conditions that can lead to destructive fires," Prof. Sharples says. "Instead of being hit hard this year, we may see the impacts of El Niño accumulate and combine with climate change in the next season and the ones following."
However, Prof. Sharples says this season may still bring a chance of significant fires developing. Three years of increased rainfall from consecutive La Niña events has seen vegetation grow, especially grasses, and a relatively dry year so far may have begun to dry it out.
"In many areas, there is still some moisture content in forest fuels like trees, leaves and branches, as well the litter on the ground, but it takes a while, probably more than one season, to dry out," Prof. Sharples says. "So, while the vegetation has grown a lot, and there may be a lot of fuel lying around, it's probably not ready to burn with that intensity this year.
"However, there are still some forested areas that have already seen significant drying, and these areas could see intense bushfires."
The Black Summer bushfires also burned a lot of forest areas along south-east Australia already. While reburn fires could occur this year, Prof. Sharples says they're unlikely to be as severe, though other untouched forest areas along the coast could still burn.
Instead, grassland areas, which have also grown over the last few years of rainfall, may be more at risk this season.
"There is a higher possibility of grass fires this year, in areas like western New South Wales, though they're not typically as damaging as large forest fires," Prof. Sharples says.
"The biggest area burnt in Australia was due to a series of grassland fires that burnt 100 million hectares following a strong La Niña, so they can still be a significant hazard, particularly in rural areas."
Future bushfire season threats
While this upcoming season might not hit as hard as others in recent memory, Prof. Sharples says the risk of more severe and frequent bushfires continues to grow from human-driven climate change.
"The fact that our worst bushfire season on record didn't coincide with an El Niño suggests climate change is acting, and we should prepare for worsening bushfire conditions in the years ahead," Prof. Sharples says.
Overall, bushfire seasons are getting longer and starting earlier. Heat waves, in particular, are becoming hotter, longer, and more frequent, drying out fuels and intensifying bushfires.
"The risk of extreme bushfires is rising because of climate change, and there is a clear link between hotter temperatures and worsening bushfires," Prof. Sharples says. "They're becoming more destructive and regular, and present a unique set of hazards as they interact with the atmosphere to create violent firestorms."
Prof. Sharples says we must act now to improve fire preparedness and management strategies to mitigate the increasing threat of bushfires.
"We're not going to be able to prevent bad seasons from occurring, but we can take steps to improve fire management techniques to prevent extreme fires as much as possible," Prof. Sharples says.
"If not, we will be locked in a vicious cycle of climate change leading to larger fires and then those larger fires amplifying the effects of climate change."
Prof. Sharples also says we need more research to understand the dynamics of fires and a lot of investment and interest in different technologies to help mitigate the risk of bushfires.
"It's not the sort of problem that gets solved in a single season," Prof. Sharples says. "It will take years, possibly even decades, of research and planning to better prepare ourselves for the kinds of bushfires we had in the Black Summer season."
Quokkas residing in the Northern Jarrah Forest, Western Australia have been found to be using fire exclusion zones to ensure their own safety and longevity.
A study conducted by researchers at Murdoch University's Harry Butler Institute, working with the Department of Biodiversity, Conservation and Attractions, has shed light on their adaptive behavior following periods of prescribed burns. The study is published in the International Journal of Wildland Fire.
The findings emphasize the importance of appropriately sized and located fire exclusion areas in conservation management.
Harry Butler Institute researcher Leticia Povh led the study and said understanding how animals use their space after prescribed burning is crucial for effective conservation management, particularly for threatened species like the quokka.
"The study aimed to determine how individual quokkas changed their home ranges following burns," Povh said.
"In a world of rising temperatures and decreasing rainfall across southwest WA, this study has important conservation significance in determining how we manage habitat for our mainland quokkas into the future."
Over the course of two years, the movement patterns of 20 quokkas were meticulously tracked before and after prescribed burns.
Home-range area calculations were performed for each individual, and behavioral change point analysis was conducted to detect any alterations in their space use.
"The key results revealed a remarkable shift in the behavior of six quokkas that had previously resided in areas subjected to prescribed burns," Povh said.
"These individuals moved into fire exclusion zones, actively avoiding the burn areas for an average of three months.
"After this time, these quokkas spent no more than 2% of their time in the burn areas. In contrast, quokkas inhabiting fire exclusion and control sites did not exhibit any changes in their space use.
"This study highlights the importance of appropriately sized fire exclusion zones to ensure the preservation of populations of species dependent on dense vegetation."
Quokkas, like many other fauna species, rely on dense cover for refuge from introduced predators such as the feral cat and red fox, making fire exclusion areas a crucial component of prescribed burn planning.
By providing refuge and food sources, these areas contribute to the long-term viability of quokka populations and other species with similar habitat requirements.
As prescribed burns continue to be used in land management, the findings of this study offer useful insights for conservation practitioners.
By incorporating appropriately sized and located fire exclusion areas into prescribed burn planning, land managers can assist in preserving critical habitat for vulnerable wildlife like the quokka.
More information: Leticia F. Povh et al, A conservation-significant threatened mammal uses fire exclusions and shifts ranges in the presence of prescribed burning, International Journal of Wildland Fire (2023). DOI: 10.1071/WF22196
Australia's iconic grass-trees—aka yaccas—are hardy, drought-tolerant, and strikingly beautiful. Now, new research has revealed another, far more important, feature: their ability to protect wildlife from deadly weather extremes.
A study undertaken by the University of South Australia and Kangaroo Island Research Station shows that the yaccas' long, thick and dry grassy skirts help insulate animals from lethal temperatures in summer and winter, as well as keeping them dry. The research is published in Pacific Conservation Biology.
Temperatures under the grass-tree canopies at four sites in the Mt Lofty Ranges were up to 20 degrees cooler than under the direct sun in summer. In winter, conditions were significantly warmer under the grass skirts at night.
It turns out the iconic plant species—Xanthorrhoea semiplana sub species semiplana—also doubles as an effective umbrella, keeping the soil completely dry under 80% of the bigger, older yaccas during weeks of heavy rain.
Lead researcher Dr. Topa Petit says it's not surprising that many creatures seek shelter under yaccas, particularly the older species with the largest and thickest skirts.
"Several of the 29 species of Australian grass-trees are known to host native bush rats, threatened bandicoots, echidnas and pygmy-possums, among other wildlife," Dr. Petit says.
"Temperatures over 40 degrees can be lethal to some of our wildlife, but grass-trees provide extremely stable temperatures with very little variation.
"The remarkable ability of these grass-trees to protect wildlife from deadly climatic extremes—as well as providing effective hiding spots from predators—strengthens the mounting evidence that these plants are keystone species."
However, the yaccas on the mainland and Kangaroo Island are facing multiple threats which could have dramatic consequences for wildlife, Dr. Petit says.
The soil pathogen Phytophthora cinnamomi is having a devastating impact on the grass-trees, causing widespread dieback. Fuel reduction programs, summer fires and land clearing are threatening their survival even further.
"Grass-tree resilience to bushfires appears to be overestimated," Dr. Petit says.
"Moreover, even if grass-trees are not killed by fires, their very old thick skirts of dead leaves burn, leaving no shelter to animals in post-bushfire environments."
In 2022, the Federal Government added fire regimes that cause declines in biodiversity to the list of Key Threatening Processes.
"Historically, grass-trees were cleared for agriculture. They are now cleared or burnt in so-called fuel reduction programs. Extensive research has shown that this practice increases fuel loads and dries out the landscape."
Dr. Petit says yaccas scorched by fire can take decades to regain their role as effective shelters and are more susceptible to Phytophthora infestations.
"It's important that habitat management be backed by sound research and scientific monitoring rather than hysteria. We owe it to the future of our ecosystems."
More information: Sophie Petit et al, The role of grass-tree Xanthorrhoea semiplana (Asphodelaceae) canopies in temperature regulation and waterproofing for ground-dwelling wildlife, Pacific Conservation Biology (2023). DOI: 10.1071/PC23014
