Invasive grasses are fueling wildfires across the US



Burning invasive, nonnative grasses on federal land at Lower Table Rock, Oregon.
BLM, CC BY

Emily Fusco, University of Massachusetts Amherst

The Santa Ana winds that help drive fall and winter wildfires in California have died down, providing welcome relief for residents. But other ecological factors contribute to fires in ways that scientists are still discovering.

I study how human actions affect fire regimes – the patterns through which fires occur in a particular place over a specific time period. People alter these patterns by adding ignition sources, such as campfires or sparking power lines; suppressing fires when they develop; and introducing nonnative invasive plants.

My research suggests that nonnative invasive grasses may be fueling wildfires across the United States. Some fires are occurring in areas that rarely burn, like the Sonoran Desert and the semiarid shrublands of the Great Basin, which covers most of Nevada and parts of five surrounding states. In the coming months, some of the grasses that help feed these blazes will germinate, producing tinder for future fires.

The Great Basin.
KMusser/Wikipedia, CC BY-SA

In a recent study, I worked with colleagues at the University of Massachusetts and the University of Colorado to investigate how 12 nonnative invasive grass species may be affecting regional fire regimes across the U.S. We found that eight species could be increasing fire in ecosystems across the country.

Altering historical fire patterns

A fire regime is a way to describe fire over space and time or to characterize fire patterns. Understanding fire regimes can help make clear that fire is a natural and integral component of many ecosystems. Knowing historical fire patterns also enables scientists to begin to understand when new or different patterns emerge.

The link between invasive grass and fire is well established. Invasive grasses are novel fuels that can act as kindling in an ecosystem where readily flammable material might not otherwise be present. They can catch a spark that might otherwise have been inconsequential.

For example, in August 2019 the Mercer Fire burned 25 acres in Arizona, scorching native desert plants, including iconic saguaro cacti. A much larger event, the 435,000-acre Martin Fire, destroyed native sagebrush ecosystems in Nevada in July 2018. Invasive grasses helped fuel both fires.

Cheatgrass, which fueled the Martin Fire, is a well-studied invasive grass known to promote fire. But many other invasive grass species have similar potential, and their roles in promoting fire have not been assessed at large scales.

How land managers are fighting invasive grasses across the Great Basin region of the West.

Introducing the suspects

Researchers describe fire regimes in many ways. Our study focused on fire occurrence (whether or not fire occurred), frequency (how many times fires occurred) and size (the largest fire associated with a place) in 29 ecological regions across the U.S. For each location we tested whether invasive grasses were associated with differences in fire occurrence, frequency or size.

A nonnative invasive species typically comes from another continent, has become established, is spreading and has negative impacts. We used an online Invasive Plant Atlas of the United States as a starting point to determine which invasive grass species to investigate.

Next, we searched the scientific literature and the U.S. Forest Service’s Fire Effects Information System to see whether there was reason to believe that any of the invasive grass species promoted fire. This process helped narrow our scope from 176 species to 12 that were suitable for our analysis.

Who are these “dirty dozen,” and how did they get here? Buffelgrass is native to Africa and was intentionally introduced to Arizona in the 1930s, probably for erosion control and forage. Japanese stiltgrass and cogongrass are native to much of Asia and were introduced to the southeastern U.S. in the early 1900s, in some instances as packing material. Medusahead, which comes from Eurasia, was introduced to the western U.S. in the late 1800s, probably by accident as a contaminant in seed shipments.

The remaining eight species – giant reed, common reed, silk reed, red brome, cheatgrass, Chinese silvergrass, Arabian schismus and common Mediterranean grass – have similar stories. People introduced them, sometimes accidentally and at other times intentionally, without an understanding of how they could impact their new settings.

Cogongrass, which is invasive in the U.S. Southeast, may burn hot enough to kill native fire-adapted tree species.
Alabama Cooperative Extension System, CC BY-ND

Big data for big questions

Understanding how multiple species influence fire over many years at a national scale requires using big data. One person could not collect information on this scale working alone.

We relied on composite data sets that provided thousands of records of invasive grass occurrence and abundance across the country. Combining these records with agency and satellite fire records helped us determine whether fire occurrence, frequency or size were different in places with and without grass invasions.

We also used statistical models to assess whether human activities and ecological features could be driving observed differences between invaded and uninvaded areas. For example, it was possible that grass invasions were happening near roads, which are also linked with fire ignitions. By including roads with grass invasion in our statistical models, we can be more confident in the role invasive grasses could play in altering fire regimes.

Our results show that eight of the species we studied are associated with increases in fire occurrence. Six of these species are also linked to increases in fire frequency. Invasions seem to be affecting a variety of ecosystems, ranging from buffelgrass in the Sonoran Desert to Japanese stiltgrass in eastern U.S. forests to cogongrass in southeastern pine systems.

Our statistical models suggest that grass invasion, along with human activities, are likely affecting fire patterns in these ecosystems.

Surprisingly, none of the invasive grass species analyzed appeared to influence fire size. We interpret this result to mean that the areas we studied are seeing more of the same types of fires that already occur there, at least in terms of size.

Dispersing seeds over a burned area of the 2015 Soda Fire in southwest Idaho to help stabilize soils and combat invasive weeds such as cheatgrass.
BLM via AP

Factoring invasive grasses into fire planning

People start an estimated 84% of wildfires in the U.S., with the rest ignited by lightning strikes. Studies show that climate change is increasing wildfire activity.

With an understanding of interactions between invasive grasses and fire, agencies that handle either fire or invasive species may find opportunities to work together to control invasions that can lead to more frequent burns. Our research can also strengthen predictions of future fire risk by incorporating the presence of invasive grasses into fire risk models.

Although it sometimes may feel as though the world is on fire, this information can provide potential for remediation, and may help communities prepare more effectively for future wildfires.

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Emily Fusco, Postdoctoral Researcher, University of Massachusetts Amherst

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Emperor Penguins could march to extinction if nations fail to halt climate change



Emperor Penguin in Antarctica.
Stephanie Jenouvrier, CC BY-ND

Stephanie Jenouvrier, Woods Hole Oceanographic Institution

The concept of a canary in a coal mine – a sensitive species that provides an alert to danger – originated with British miners, who carried actual canaries underground through the mid-1980s to detect the presence of deadly carbon monoxide gas. Today another bird, the Emperor Penguin, is providing a similar warning about the planetary effects of burning fossil fuels.

As a seabird ecologist, I develop mathematical models to understand and predict how seabirds respond to environmental change. My research integrates many areas of science, including the expertise of climatologists, to improve our ability to anticipate future ecological consequences of climate change.

Most recently, I worked with colleagues to combine what we know about the life history of Emperor Penguins with different potential climate scenarios outlined in the 2015 Paris Agreement, to combat climate change and adapt to its effects. We wanted to understand how climate change could affect this iconic species, whose unique life habits were documented in the award-winning film “March of the Penguins.”

Our newly published study found that if climate change continues at its current rate, Emperor Penguins could virtually disappear by the year 2100 due to loss of Antarctic sea ice. However, a more aggressive global climate policy can halt the penguins’ march to extinction.

Emperor Penguins breeding on sea ice in Terre Adélie, Antarctica.
Stephanie Jenouvrier, CC BY-ND

Carbon dioxide in Earth’s atmosphere

As many scientific reports have shown, human activities are increasing carbon dioxide concentrations in Earth’s atmosphere, which is warming the planet. Today atmospheric CO2 levels stand at slightly over 410 parts per million, well above anything the planet has experienced in millions of years.

If this trend continues, scientists project that CO2 in the atmosphere could reach 950 parts per million by 2100. These conditions would produce a very different world from today’s.

Emperor Penguins are living indicators whose population trends can illustrate the consequences of these changes. Although they are found in Antarctica, far from human civilization, they live in such delicate balance with their rapidly changing environment that they have become modern-day canaries.

A fate tied to sea ice

I have spent almost 20 years studying Emperor Penguins’ unique adaptations to the harsh conditions of their sea ice home. Each year, the surface of the ocean around Antarctica freezes over in the winter and melts back in summer. Penguins use the ice as a home base for breeding, feeding and molting, arriving at their colony from ocean waters in March or April after sea ice has formed for the Southern Hemisphere’s winter season.

54 known Emperor Penguin colonies around Antarctica (black dots) and sea ice cover (blue color).
Stephanie Jenouvrier, CC BY-ND

In mid-May the female lays a single egg. Throughout the winter, males keep the eggs warm while females make a long trek to open water to feed during the most unforgiving weather on Earth.

When female penguins return to their newly hatched chicks with food, the males have fasted for four months and lost almost half their weight. After the egg hatches, both parents take turns feeding and protecting their chick. In September, the adults leave their young so that they can both forage to meet their chick’s growing appetite. In December, everyone leaves the colony and returns to the ocean.

Emperor Penguin fathers incubate a single egg until it hatches.

Throughout this annual cycle, the penguins rely on a sea ice “Goldilocks zone” of conditions to thrive. They need openings in the ice that provide access to the water so they can feed, but also a thick, stable platform of ice to raise their chicks.

Penguin population trends

For more than 60 years, scientists have extensively studied one Emperor Penguin colony in Antarctica, called Terre Adélie. This research has enabled us to understand how sea ice conditions affect the birds’ population dynamics. In the 1970s, for example, the population experienced a dramatic decline when several consecutive years of low sea ice cover caused widespread deaths among male penguins.

Over the past 10 years, my colleagues and I have combined what we know about these relationships between sea ice and fluctuations in penguin life histories to create a demographic model that allows us to understand how sea ice conditions affect the abundance of Emperor Penguins, and to project their numbers based on forecasts of future sea ice cover in Antarctica.

Once we confirmed that our model successfully reproduced past observed trends in Emperor Penguin populations around all Antarctica, we expanded our analysis into a species-level threat assessment.

Climate conditions determine emperor penguins’ fate

When we used a climate model linked to our population model to project what is likely to happen to sea ice if greenhouse gas emissions continue on their present trend, we found that all 54 known Emperor Penguin colonies would be in decline by 2100, and 80% of them would be quasi-extinct. Accordingly, we estimate that the total number of Emperor Penguins will decline by 86% relative to its current size of roughly 250,000 if nations fail to reduce their carbon dioxide emissions.

Without action to reduce global carbon dioxide emissions, sea ice loss (shown in blue) will eradicate most Emperor Penguin colonies by 2100.
Stephanie Jenouvrier, CC BY-ND

However, if the global community acts to reduce greenhouse gas emissions and succeeds in stabilizing average global temperatures at 1.5 degrees Celsius (3 degrees Faherenheit) above pre-industrial levels, we estimate that Emperor Penguin numbers would decline by 31% – still drastic, but viable.

Less-stringent cuts in greenhouse gas emissions, leading to a global temperature rise of 2°C, would result in a 44% decline.

Our model indicates that these population declines will occur predominately in the first half of this century. Nonetheless, in a scenario in which the world meets the Paris climate targets, we project that the global Emperor Penguin population would nearly stabilize by 2100, and that viable refuges would remain available to support some colonies.

Global action to limit climate change through 2100 could greatly improve Emperor Penguins’ persistence/viability.
Stephanie Jenouvrier, CC BY-ND

In a changing climate, individual penguins may move to new locations to find more suitable conditions. Our population model included complex dispersal processes to account for these movements. However, we find that these actions are not enough to offset climate-driven global population declines. In short, global climate policy has much more influence over the future of Emperor Penguins than the penguins’ ability to move to better habitat.

Our findings starkly illustrate the far-reaching implications of national climate policy decisions. Curbing carbon dioxide emissions has critical implications for Emperor Penguins and an untold number of other species for which science has yet to document such a plain-spoken warning.

[ You’re smart and curious about the world. So are The Conversation’s authors and editors. You can read us daily by subscribing to our newsletter. ]The Conversation

Stephanie Jenouvrier, Associate Scientist, Woods Hole Oceanographic Institution

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Aussie scientists need your help keeping track of bees (please)



The Asian honey bee (Apis cerana) has been found in Cairns. It’s just one of the introduced bees buzzing under the radar.
Tobias Smith, Author provided

Manu Saunders, University of New England; Callum McKercher, University of New England; Mark Hall, Western Sydney University; Tanya Latty, University of Sydney, and Tobias Smith, The University of Queensland

Bees get a lot of good press. They pollinate our crops and in some cases, make delicious honey. But bees around the world face serious threats, and the public can help protect them.

Of more than 20,400 known bee species in the world, about 1,650 are native to Australia. But not all bees found in Australia are native. A few species have been introduced: some on purpose and others secretly hitchhiking, usually through international trade routes.

As bee researchers, we’ve all experienced seeing a beautiful, fuzzy striped bee buzzing about our gardens, only to realise it’s an exotic species far from home.




Read more:
The farmer wants a hive: inside the world of renting bees


We need the public’s help to identify the bees in Australian backyards. There’s a good chance some are not native, but are unwanted exotic species. Identifying new intruders before they become established will help protect our native species.

The European honey bee (Apis mellifera) fuels a valuable honey industry and contributes to agricultural pollination. Other introduced species are far less welcome.
Tobias Smith

Exotic bees in Australia

The European honey bee (Apis mellifera) is the best-known introduced species, first brought to Australia in the early 1800s. It is now well-established throughout the country, with profitable industries built around managed populations.

Other invasive species in Australia are less well known (or loved). The European bumblebee (Bombus terrestris) is present in high numbers in Tasmania, but isn’t thought to be established on mainland Australia.

This bumblebee has caused major harm to native bees in South America, competing for resources and spreading disease.

In northern Queensland, the Asian honey bee (Apis cerana) is established around Cairns and Mareeba, from a single incursion in 2007. The original founding colony is thought to have been a stowaway on a boat that sailed to Cairns from somewhere in southeast Asia or the Pacific, where this bee is widespread.

New Asian honey bee incursions at Australian ports occur almost annually, most recently in Townsville and Melbourne. But swift biosecurity responses have so far stopped them becoming established.

The European bumble bee (Bombus terrestris) lives in large numbers in Tasmania, but is not established on the mainland.
Tobias Smith, Author provided

Why should we care?

Most insects can spread and establish breeding populations before anyone notices them, so it’s important we pay attention to these small intruders.

Introduced species can bring new parasites or diseases into the country that may harm native insects – including our stingless bees that are so vital to crop pollination – or affect the valuable European honey bee industry.

While bumblebees may help commercial pollination in a handful of Australian crops, they and other introduced species can also compete with native species for resources, or spread weeds.

Most resources go to monitoring invasive species with a more dramatic and understood effect on agriculture and the environment. Bees sneak under the radar – but we’re still curious.

Take the African carder bee (Pseudoanthidium repetitum), which arrived in Australia in the early 2000s. Thanks to citizen scientists, we know they are spreading rapidly. In 2014, they were the third most common bee species found in a survey of Sydney community gardens.

An African carder bee spotted in Lismore. They are the third most common bee species in Sydney community gardens.
Tobias Smith, Author provided

Just recently, we found two invasive African carder bees in a backyard in Armidale in northern New South Wales while testing out a new insect monitoring method. There are no confirmed records of this invasive bee in Armidale, although we have seen a few around town since 2017.




Read more:
Bees: how important are they and what would happen if they went extinct?


Although it’s usually exciting to find a new record for a native species, finding an exotic bee where it’s not supposed to be is worrying. How long have they been there, and how many others are there?

The European bumble bee was recently sighted to global biodiversity.

You don’t have to be totally sure what kind of bee you’ve spotted. Just snap some pictures and upload it to a citizen scientist app like iNaturalist with the date and location.
Jean and Fred/Flickr, CC BY

Will you help us keep track?

Anyone can help keep track of potential new invasive species, simply by learning more about the insects in your local area and sharing observations on citizen science platforms such as iNaturalist, or through targeted projects like the African carder bee monitoring project.

You don’t need to be sure exactly what species you’ve seen. Uploading some clear, high-resolution photos, along with the date and location of your observation, will help naturalists and researchers identify it.




Read more:
Wasps, aphids and ants: the other honey makers


You can also participate in events such as the twice-yearly Wild Pollinator Count or local Bioblitzes.

Your efforts can help us detect emerging threats, and add to our records of both native and non-native bees (and other species). Plus it’s a great excuse to get outdoors and learn more about the insect life in your area.


This article was co-written with Karen Retra.The Conversation

Manu Saunders, Research fellow, University of New England; Callum McKercher, PhD Student, University of New England; Mark Hall, Research fellow, Western Sydney University; Tanya Latty, Associate professor, University of Sydney, and Tobias Smith, Ecologist, bee researcher and stingless bee keeper, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.