Posts Tagged ‘Invasive Species’

An adult Spotted Lanternfly. Photo: Wikipedia.

Are you a fan of apples, beer, maple wood furniture, or peaches? The plants that produce these products, and many more species, are at risk from a threat that is spreading across North America. What is this threat? It is a rather beautiful insect call a Spotted Lanternfly (Lycorma delicatula).

The Spotted Lanternfly was first detected in North America in 2014 when a few were spotted in Pennsylvania. Between 2014 and today, they have spread to 11 more states and are now also found in Connecticut, Delaware, Indiana, Maryland, Massachusetts, New Jersey, New York, North Carolina, Ohio, Virginia, and West Virginia.

This insect, which is not actually a fly but rather a species of planthopper, is native to China, but has spread to Japan, South Korea, and the USA and is becoming a significant agricultural pest in these other countries.

In its native China, this species is not a major issue because its population is generally kept in check by several species of parasitic wasp that feed on the Spotted Lanternfly. However, these wasps are not present in the new areas the lanternfly has spread to which has resulted in their population increasing and spreading rapidly.

Spotted Lanternfly egg mass. Photo: Rutgers University.

Spotted Lanternflies do not fly long distances on their own, so adults do not disperse very far. However, the species is very effective at dispersing via their eggs. Adult Spotted Lanternflies lay their egg masses on all sorts of objects from trees to houses to vehicles. They can even end up getting scrapped off of these structures and stuck to shoes and clothing. in this way, egg masses can be transported long distances and so introduce the species into new areas rapidly.

Luckily, the Spotted Lanternfly poses no direct threat to humans or animals. However, they suck the fluids from many species of plant which can weaken an kill them. Many of these plant species are of significant economic value, and many more create extensive and important habitat for countless other animals, plants, fungi, etc. The list of plant species that are susceptible to Spotted Lanternfly infestations includes: Almonds, Apples, Apricots, Cherries, Grapes, Hops, Maple Trees, Nectarines, Oak Trees, Peaches, Pine Trees, Plums, Poplar Trees, Sycamore Trees, Walnut Trees, and Willow Trees.

Spotted Lanternfly life cycle stages. Photo: spottedlanternflykillers.com

Control efforts are underway, and extensive help from all of us will be needed to stop the spread of this insect. The state of Pennsylvania has even step up a hotline number to call and report sightings which is 1-888-4BADFLY. Control efforts include taking extra care to clean objects that could have egg masses attached to them. This is particularly important for anything passing through areas of known Spotted Lanternfly infestations. We should all make sure to clean our cars, boats, trailers, tents, clothing, shoes, and other materials if we are moving them from or through any of the above states. Without serious control efforts, the Spotted Lanternfly is predicted to continue to spread and is likely to reach California around 2033.

If you do find adult Spotted Lanternflies it is recommended that they be killed. They are fast, so we will all have to work on our reflexes. If an egg mass is found, scrape it off and put it into a sealed plastic bag with hand sanitizer (good thing we all have this around so much these days!).

So, keep your eyes open for this insect, help control their population and spread, and report any sightings! In this way we can all help to protect our forests and farms.

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Mute Swans (Cygnus olor) are a species that is growing more and more numerous, and this is a problem.

Mute Swans are the “classic” swan from stories and art. They are large and showy and beautiful and these traits are exactly why they have been introduced to North America. Birds were brought from Europe in the 1800s and released in parks, gardens, etc. as ornamental additions (New York was the original release area). These birds have since reproduced and spread across the continent as far north as New Hampshire, as far south as Florida, and as far as west as California.

Adult male Mute Swan (Cygnus olor). Source: USFWS digital library.

They are becoming problematic for several reasons. One is that they are quite aggressive, and will chase and bite humans if that human trespasses on the swan’s territory. Another is that they consume quite a bit of food. They are big birds reaching up to 25 to 30 pounds, and that means they eat about eight pounds of aquatic vegetation every day. That is food which is then not available to native birds, and it disrupts habitat for native birds, mammals, fish, and other species. And a third reason is that the swans are directly aggressive to other species of bird driving them off nests, breaking eggs, and killing the chicks of other species, and so displacing those other species from areas where they would otherwise live. With habitats becoming ever smaller and more fragmented, this can mean the native species can be left with no where to go.

These problems have all contributed to Mute Swans being added to California’s restricted species list in 2008. This listing means the birds cannot be imported, transported, or possessed in the state without a permit. This has not completely prevented the swans from beginning to become established in California. Small populations can be found in Petaluma and the Suisun Marsh. I suggest that removing this species while the population is still small is the best course of action. There is every reason to suspect that the population will grow, and as it does so, the problems listed above will become more and more apparent. However, control will become more and more difficult.

One interesting thing about Mute Swans in North America is that they do not migrate very much. There are certainly some, relatively short, seasonal movements that occur in some parts of the continent, but not much. Certainly nothing compared to the long migrations that Mute Swans in Europe engage in. The evolution of this behavior in a novel environment illustrates how different geographic regions can cause a species to adapt and change. This behavioral evolution could then lead to the evolution of a new species, if it persists and becomes dramatic enough.

So, what can you do to help native birds and habitats, and prevent Mute Swans from taking over? If you spot a Mute Swan in California, contact the California Department of Fish and Wildlife – Invasive Species Program by sending an email to: invasives@wildlife.ca.gov or calling 886-440-9530. Together, we can act as citizen scientists to gather data that tracks where these birds are and how they move around. This data will help us all make the best and most informed decisions we can about this species.

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The management of wild horses and burros is a topic that I have felt strongly about for a long time. I can sympathize with those who see the horse as a symbol of the American West, of independence, and of strength and beauty. However, that sympathy does not last very long or go very far.

Image result for wild horses of nevada

A group of wild horses in Nevada.

The wild horse and the wild burro in North America are invasive species. Plain and simple. As such, it is my opinion that those invasive populations should be controlled so as not to negatively impact native species or the overall health of the ecosystem.

The Wildlife Society has recently produced a short documentary called “Horse Rich & Dirt Poor” that lays out some of the issues surrounding horse management in the USA.

One of the points that the film makes is that under current policies and procedures, everyone (native mammals, native birds, native fish, native plants, the land itself, and even the wild horses and burros) is loosing.

Give this 15 minute video a watch, and think about where we are. Where do you think we should go? How do you think we should get there?


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A study was published earlier this month in the journal Frontiers in Ecology and the Environment on the effects that invasive species have on other species around the globe. The study is by Tim M. Blackburn, Celine Bellard, and Anthony Ricciardi, and it can be found here.

The main thrust of the paper is that invasive species of plants and animals have been found to have a significant impact on the extinction of other plants and animals all around the world. Specifically, 25% of the plant species that have gone extinct in recent years have been the result, at least in part, of invasive species. Additionally, 33% of the animal species that have gone extinct in recent years have been the result, at least in part, of invasive species.

These numbers are pretty compelling components to the story of just how damaging invasive species can be. It is part of the reason I find working on invasive species control in California to be rewarding.

I am currently working on the control of Arundo (which is a large invasive reed), water primrose (an invasive aquatic plant), Phragmites (which is another invasive reed that is a bit smaller than Arundo), and Nutria (which is a 20 pound semi-aquatic rodent). Each of these species pose unique threats to the native species of California and to many other aspects of the ecosystem as well.

Hopefully, protocols can be developed to stop invasive species before they contribute even more extinctions!

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Delta Conservancy Logo 3The Sacramento-San Joaquin Delta Conservancy (the state agency where I work), which is based in West Sacramento, is currently looking to hire a Senior Environmental Scientist (Specialist)! The position is heavily involved with invasive plant work, particularly focusing on Giant Reed (Arundo donax) in the Delta. It will also be quite involved with managing Proposition 1 grants for habitat restoration, water quality improvement, and sustainable agriculture projects.

If you are interested, or know someone who might be, please check out the official job posting here. It is a great agency to work for!

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IMG_20170829_091735[1]Along with about 125 other scientists, researchers, and managers, I spent most of last Tuesday attending the Delta Invasive Species Symposium hosted on the U.C. Davis campus and organized by the Delta Stewardship Council, U.C. Davis, and the Delta Interagency Invasive Species Coordination Team.

It was a very interesting symposium that included talks, posters, and a terrific panel discussion. Topics covered a wide range of invasive species ecology, invasive species management techniques and efforts, the effects of invasive species on natural communities and human society, and how invasive species are likely to be effected by climate change.

There are a huge number of invasive species in the Sacramento-San Joaquin Delta. This list includes plants like Water Hyacinth and Giant Reed, vertebrates such as Northern Watersnake and Stripped Bass, invertebrates like Asian Gypsy Moth and Spotted Lanternfly, and many many others.

Dealing with the effects of these invasive species, and attempting to control their populations, costs millions of dollar every year.

Given these high costs, prevention is without doubt the best technique when dealing with invasive species. The costs of measures that are undertaken to prevent an invasive species from entering an area, the Delta for example, are certainly going to be less than the costs of controlling that species once it becomes established. Many efforts are being undertaken in the Delta to keep new invaders from entering. This is especially important because many invasive species are currently found near the Delta, that could become huge problems in they show enter the Delta system. Nutria are an example of this. The Nutria is a large rodent native to South America. A population was established in the southern Sierra in the hope of crating a source for furs, but the furs of Nutria did not catch on in the market place, and the effort was abandoned. The Nutria that had been released were hunted and almost completely exterminated in the 1960s, but small numbers have started showing up along the Merced and  San Joaquin Rivers. If those populations are allowed to grow and spread, they will cause massive damage to the Delta ecosystem because of the feeding habits of Nutria which can leave extensive tracts of wetlands denuded of vegetation.

The next best technique is early detection and rapid responses. If an invasive species is expanding its geographic range, having lots of observations of where it is occurring is immensely useful. Knowing exactly where, when, and how many individuals are out there can mean that, with a swift response, it may be possible to control their numbers. This is where the value of citizen science networks is particularly dramatic. There is no way that professional biologists will be able to cover a whole area at small enough detail and high enough frequency to realistically be able to watch for any and all invasive species. But with online databases and citizen scientists out in the field, there may be enough eyes to pick up on new invasive arrivals. Projects like eBird, Calflora, and others allow individuals to add their observations together to form an enormous and very thorough observation net.

One reason that tracking and responding to invasive species is so important is the effects that they have on native species. Competition with invasive species is the second most common reason for species to be placed on the Endangered Species List (behind habitat destruction), and invasive species interactions are a contributing factor for listing 1/3 of all listed species!

And it is only going to get worse. Global climate change is opening up large areas that used to be unlikely places for invasive species to get a foothold. Alaska is just such a place. Historically, places like Alaska had harsh enough environments that, generally speaking, only species that had evolved with those conditions did well. With the warming climate, these harsh conditions that have protected such areas are becoming less harsh. Elodea is an aquatic plant that is often considered an invasive due its rapid growth rates and its tendency to exclude other species from an area. Historically, it was not found in Alaska at all, but in the past few years has started to appear in parts of the state.

All in all, I learned a lot at the symposium. There are definitely a lot of threats and dangers posed by invasive species in the Delta and many more from invasive species that are not currently present should they enter the Delta ecosystem. But there is also so much that can and is being done by dedicated professionals in the field, and also by communities and citizen scientists who care about the natural ecosystems in which we all live.

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I have written about the conflict between Spotted Owls (Strix occidentalis) and Barred Owls (Strix varia) a couple of times before (here and here). The basic situation is that Barred Owls (generally native to eastern North America) have been expanding their range into the range of the Spotted Owl (western North America) for the past 40 years or so. The Spotted Owl has been declining for a long time and two of the three subspecies are federally listed as Threatened under the U.S. Endangered Species Act. The intrusion of Barred Owls is now a big problem for the Spotted Owls for several reasons.

Spotted Owl - USFWS

A subadult Spotted Owl (photo by USF&WS)

One reason is that the total Spotted Owl population is smaller than the total Barred Owl Population, and small populations are more at risk of declines and extinction. Another reasons is that the Barred Owls are bigger and more aggressive than Spotted Owls and push the Spotted Owls out of nesting territories. Sometimes the Barred Owls are big enough and aggressive enough that they eat the Spotted Owl. Yet another issue is that the two species of owl are so closely related that they can hybridize and produce so called Sparred Owls. This genetic mixing has much more profound implications for the long term persistence of the Spotted Owl than the Barred Owl due the much smaller population size of the the former.

The primary solution that has been proposed to save the Spotted Owl from extinction has been to alter logging practices and set aside the old-growth forests that the Spotted Owls depend on. However, this has not been enough to halt the Spotted Owl decline. An additional plan that the U.S. Fish & Wildlife Service has been pursuing is the lethal removal of Barred Owls from areas where Spotted Owls are nesting or have nested in the recent past. From 2009 to 2013, USF&WS scientists killed approximately 90 Barred Owls. This had a marked effect on the Spotted Owl population. In areas where Barred Owls were removed, Spotted Owl population levels did not change any more than in areas where Barred Owls had never been observed. Also, territories that were held by the removed Barred Owls were fairly quickly re-occupied by Spotted Owls.

This result is a surprise to me. In my past posts, I was quite critical of the plan, and was skeptical that the removal of Barred Owls would actually benefit Spotted Owls. The results of the removal study suggest that this strategy might work to preserve Spotted Owls. But there are still problems.


An adult Barred Owl (photo by Ashley Hockenberry)

Spotted Owls respond well to the removal of their Barred Owl competitors. But how will these removals be maintained? Shooting Barred Owls takes a fairly considerable effort, so there is no way that this process can be enacted over the whole range of the Spotted Owl. It will not be possible to even do it over large areas. Instead, the only way that this plan will be able to be put into practice will be on very small areas of core Spotted Owl habitat. The other problem is one of time. To be effective, these core areas will have to be patrolled regularly, forever. New Barred Owls are perfectly capable of re-invading areas where the earlier Barred Owl inhabitants had been shot, and they will do so in short order.

So, much of my skepticism and critiques from my earlier posts still stand. I do not think that killing Barred Owls is a long-term solution for Spotted Owls on really any scale that will be useful for the survival of the species. It will simply require more time, effort, and money than anyone has to devote to the issue. That having been said, the fact that killing Barred Owls made any impact on Spotted Owls at all is more than I thought would happen.

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I have been working at the Sacramento-San Joaquin Delta Conservancy for about four months now, and it occurred to me that I have not shared much of what the Delta Conservancy, and I in particular, have been doing in that time. My start here has certainly included a steep learning curve as I have become more familiar with the agency, my coworkers, and the many projects that the Delta Conservancy is pushing forward.


Figure 1. A stand of Arundo.

I am starting to feel my feet under me, and wanted to share some the projects I am working on. So, first up is the Arundo Control and Restoration Project. This is a project that was started before I was hired and was managed by one of the other employees here at the Delta Conservancy. About a month after I started working here, she took a job elsewhere, and the Arundo Project was transferred to me.

Arundo donax, or Giant Cane, is an invasive plant native to the Mediterranean and Middle East, and which was introduced to southern California for building material and in the hope that it would grow along levees and help with flood and erosion control. Unfortunately, while it did grow extensively along levees, it did not help with flood and erosion control. Instead, it actually had the opposite effect. While it will grow into dense mats, these mats have shallow root systems, so when high flows occur, the strong currents tend to rip off large chunks of Arundo which then rips off large chunks of the levee underneath. Additionally, Arundo forms dense mono-culture stands, out competes native vegetation, and provides little useful habitat.

To start to remedy the situation and role back these negative effects, the Delta Conservancy’s Arundo Control and Restoration Project was founded.

Arundo Sites in the Delta - Map

Figure 2. Map of Arundo donax sites in the Delta (Young et al. 2015).

The overall plan is to figure out where Arundo is growing in the Delta, prioritize those sites to figure out which could provide the highest value habitat if the Arundo was removed, remove Arundo, and replace it with restored native vegetation. The native vegetation will be restored on the same areas where Arundo is removed from, except where this is not feasible due to landowner restrictions and land use policies. When it is not possible to directly replace existing Arundo stands with restored vegetation at the same location, restoration will occur at nearby sites that will be prioritized according to their habitat value.

Contracting with the Sonoma Ecology Center, the Delta Conservancy has completed the map of Arundo sites in the Delta (Figure 2) and also prioritized those sites according to their restoration value (Figure 3). As you can see in Figure 3, the darker the colored dot, the more potential value that area has if the Arundo is removed and native vegetation is restored.  

Arundo Sites in the Delta - Prioritized Map

Figure 3. Map of Arundo donax sites in the Delta prioritized by color (Young et al. 2015).

As is evident from these maps, there is quite a bit of Arundo in the Delta. Attempting to tackle all of it simultaneously seems a herculean task, so the total project was divided into two phases. Phase I is the pilot project phase. In Phase I we planned to locate a subregion of the Delta that contained Arundo, and develop our protocols and techniques to effectively control Arundo and implement habitat restoration work. Phase II would then be a significant expansion of Phase I into more regions of the Delta.

We are currently in the midst of Phase I. Based on the information in the above maps, and on opportunities to find land owners who had Arundo on their property and were willing to grant us access to work, the Delta Conservancy partnered with the Solano Resources Conservation District (Solano RCD) in identifying the Cache Slough Complex (CSC) as a prime region for Phase I to occur. We are currently working on a stretch of Ulatis Creek in Solano County. Ulatis Creek runs southeast out of Vacaville, CA for about 20 miles before emptying into Hass Slough and then into the Sacramento River. For almost all of its length, Ulatis Creek is constrained between levees on either bank. About 15 miles southeast of Vacaville, at a bend in the creek, there is an area where the levee on the north bank is set back a few hundred feet from the creek channel. In between this setback levee and the regular bank of the creek, and extending along the north shore, is an area of about 18 acres. Part of this 18 acres is covered in Arundo and the rest is used, intermittently, to graze sheep by the property owner.


Figure 4. Ulatis Creek site. Sheep are grazing and the dense vegetation along the far edge is almost all Arundo.

This 18 acre area has been chosen, thanks to a willing private landowner, as the first stage of Phase I. In 2015, 3.77 acres of Arundo at the western end of the site were treated with an herbicide for the first time. Successful Arundo control has been shown to require two or three treatments to completely kill the plants in an area. This summer and fall, the Solano RCD will begin clearing non-native vegetation, laying out irrigation lines, and planting native vegetation. This native vegetation will take the form of somewhere on the order of 1500 trees of a mix of species and native understory species such as California Rose and Mugwort. Riparian trees will be planted along the perimeter of the site which will grow to shade the waterway and stabilize the banks. In the middle of the area, oaks and other upland tree species will be planted to create a more varied habitat pallet in the area. All these plants will then need several years of watering to make sure they are well established. This time also gives us the opportunity to replace plants that die.

If we are successful, and the removal of Arundo and establishment of native vegetation goes well, we will be well on our way to extending this effort to more areas of the Delta. Overall, this effort will replace areas of low habitat value and high potential for economic and environmental costs with areas of high habitat value that can be utilized by  a large range of species and better foster the ecosystem and sustainable economy of the Sacramento-San Joaquin Delta. I am excited to watch this project unfold as we move forward!


Young, A., B. Sesser, and C. Liu. 2015. Delta Arundo mapping and prioritization. Sonoma Ecology Center.


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My wife and I just returned from a short trip to Ashland, OR and surroundings.  It was a great trip filled with Shakespeare, rain, hiking and birds!  We have visited this region every year for several years now, and this year there was a new arrival there waiting for us…Eurasian Collared-Doves.  Lots of them!  This non-native species has been spreading quite dramatically across North America in recent years.  A small, but growing, population has been breeding in Davis, CA for the past few years.  The existence of this species in North America is largely the result of escaped birds that decided not to return to their cages.  As a result, this invasion started in large urban areas.  In California, San Francisco, Los Angeles, and San Diego were the first locations that reported having feral groups of these birds.  The range that this increasing population covers has been growing faster and faster, and this is the first time I have seen them in southern Oregon.  They were all over Ashland and Jacksonville and the smaller towns in between.  How this species interacts with the native Mourning Dove or Whtie-winged Dove, or the fellow invasive Rock Pigeon has not been studied, but it seems that these species have close enough natural histories that interactions will occur, and since the Eurasian Collard-Dove population in increasing, it seems likely that some or all of the others are suffering.  So, keep an eye out for this large pale-gray dove, and also take time to notice how many Mourning Doves you see around.  The earlier we can catch on to a possible problem, the more likely we are to be able to influence the eventual outcome.

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