Matthew Sarver » Bees

Knocking Out Knapweed

Matthew Sarver — Fri, 07 Aug 2009 04:44:42 +0000

Another July has come and gone, but not all of the fireworks are over. The striking pink display of spotted knapweed, Centaurea stoebe ssp. micranthos, is still going strong in rangelands and old fields and along highways and railroad grades across the country. Native to Europe, spotted knapweed was introduced accidentally to North America in the late 19th century, and has since become a problematic invasive weed, especially in the west.

The pinkish-violet blossom of spotted knapweed.

I first noticed knapweed blooming on our wildlife sanctuary property in Pennsylvania about five years ago, at the same time that I started to seriously consider the possibilities for habitat management on the site. Knapweed control was one of my first projects on the property. Since I knew that mowing was counter-productive (causing the plants to flower at a lower height), I decided to pull the knapweed by hand. I’ve repeated the process for four years, and have eliminated spread of the plant while steadily reducing the seed bank at the main introduction site. Because spotted knapweed seedlings assume a low-growing rosette form during their first year and don’t bolt and bloom until their second year or later, I’ve been able to track my success by noting a significant reduction in rosettes (a few dozen this year compared to countless hundreds during the first year of two of treatment).

Unfortunately, Spotted Knapweed is a highly favored bee plant, used heavily by native bumblebee species. It’s always emotionally taxing for me to pull, bag and dispose of the knapweed with bumblebees crawling all over the blossoms as I work. This brings me to one of my take-home messages in invasive species control and restoration: in degraded habitats, native species often rely heavily on invasive plants because the diversity of native plants has been reduced. It is important to know what native insect and wildlife species rely on the invasive plant you are removing. Then, when planning a restoration, try to plant (or enhance habitat for) native plants that provide resources at the same time of year as the invasive. In my case, I’m working on restoring some meadows that will hopefully make up for (from a bee perspective) the eventual disappearance of my knapweed stand.

Spotted knapweed is an invasive plant, but is used extensively by native bumblebees

Since I’ve been working on this population for several years with a good deal of success, I thought I’d share a brief description of my spotted knapweed manual removal method.

Here are a few important points:

Get a good digging tool – I have tried various things – heavy clawhammers to grab and yank roots, various hand tiller/weeder/fork type things, etc. I’ve recently settled on a well-balanced, heavy-duty, and inexpensive digging tool (see the photo below) that I picked up at the friendly neighborhood home improvement warehouse.
Pull plants during their bloom period and before they’ve gone to seed. Be sure to bag and dispose of the plants in a landfill, to avoid dispersing seed or root fragments. A good rain just before (or even during) pulling makes the job much easier.
Be patient when pulling and learn to stop and dig more when you feel that the root is about to snap. Pieces of root left in the ground will sprout the following year.
Don’t dig right at the base of the plant – you risk cutting through the root, which often twists to one side or another a few inches down. Instead, loosen the soil about 5-6 inches from the base of the plant.

Here’s the process illustrated:

This is my tool of choice: a beveled, pointed blade on one end (used the most) and a straight blade on the other. The pointed blade sinks well into the shale soils where my infestation occurs.

Many stems usually radiate from a single root crown of older Spotted Knapweed plants. It's important to gather all the stems up to get a good grip on the plant for pulling.

Strike the ground about 5-6" from the base of the plant and loosen the soil, prying up with the tool while pulling straight up on the plant. Pulling at an angle makes it more likely that you'll break the root.

The root system should pull up cleanly if you loosen the soil enough and slowly pull upward on the plant.

The root crown can be quite broad on robust plants, or much smaller with fewer fibrous roots on stressed plants.

Please let me know if you have had success with other spotted knapweed control methods. I have considered trying Milestone, a selective herbicide that is supposedly quite effective on both knapweed and thistles. So far, I haven’t needed to resort to spraying though, since manual removal has been working well and at this point only takes me about a day each year to complete. Now if only I could eliminate my crown vetch, smooth brome, and reed-canary grass this easily!

Take Me to the River

Matthew Sarver — Sat, 04 Jul 2009 20:28:50 +0000

I’m headed to the Catskills to enjoy the woods and the river for a few days. Last year I did a lot of botanizing, mothing, and bee photography. Hopefully this year will be even better!

Fishing in the Catskills

Biofuels and Habitat Loss

Matthew Sarver — Tue, 30 Jun 2009 20:43:34 +0000

Renewable. Sustainable. Green.

All of these buzzwords make us feel good about our progress toward mainstreaming alternative energy sources. We need to power an increasingly energy-hungry world in the face of global climate change, and we all know that fossil fuels are not the solution.

What often gets lost in the excitement surrounding “green” energy, though, is that these technologies are not free from collateral damage to biodiversity and wildlife habitats. Wind turbines atop Appalachian ridges, for instance, may impact unique mountain-top habitats, and they are known to kill birds and large numbers of migrating bats. As pressure has been building on wind farm operators to address this problem, basic steps are being taken to help reduce the impact. Common sense solutions like shutting down the turbines on relatively calm nights are apparently effective at reducing bat kills, for example.

Biofuels are not without their problems, either, but the problems have largely gone unrecognized, and the solutions are not as straightforward. From a climate change perspective, one major issue is the increase in emissions caused by land use changes associated with biofuel production. This is the focus of a current campaign by the Union of Concerned Scientists. At the “Take Action” section of their site, you can personalize and send a letter to the EPA, urging the agency to consider land use changes when calculating life-cycle analyses of biofuels for the agency’s Renewable Fuels Standard (RFS).

What the UCS letter doesn’t directly address is the impact of those same land use changes on other ecosystem services, wildlife habitat, and biodiversity. European studies have shown that production of biofuel crops such as corn in the amounts necessary to meet EU targets is generating significant negative impacts on biodiversity.

The production of so-called second-generation biofuels from grasses is somewhat less detrimental, but still far from ideal. As cellulosic biofuel production becomes more cost-effective and energy efficient, switchgrass, a high-yield, perennial grass, is poised to become an important commodity here in the U.S.

Switchgrass (left) is poised to surpass Corn (right) as the commodity of choice for production of ethanol for biofuel. Photo by USDA ARS Photo Unit, USDA Agricultural Research Service, Bugwood.org (used under a Creative Commons 3.0 Attribution License)

Switchgrass (Panicum virgatum) is a tall, native warm-season grass that was once widespread throughout the American tallgrass prairie. Today, many cultivars are available, and the species is used for conservation plantings and wildlife habitat, providing valuable food and cover for birds and other wildlife. So what’s the problem? When grown in a monoculture, as required for harvesting for biofuels, switchgrass is only marginally better wildlife habitat than corn, or any other crop.

Native prairies were historically very diverse plant communities, with species composition maintained by periodic fires. Structurally, native grasslands varied in density and height based on fire history, soils, and other factors. Many grassland birds of conservation concern require patchy bunchgrasses with some bare ground in between plants. Native bees require a diversity of wildflowers that bloom at different times throughout the year, as well as access to bare soils for nesting. Butterflies all require different species of hostplants on which their caterpillars can grow. In short, grassland biodiversity depends on both structural and species diversity of the plant community. Monocultures just don’t cut it.

Grasshopper Sparrow (Ammodramus savannarum) and other grassland birds are at risk from high biofuel commodity prices. Photo (c) Jeffrey A. Gordon

So what’s at stake? The concern of many conservationists (myself included) is the potential conversion of privately-owned land that is currently enrolled in federal conservation programs to switchgrass monocultures for biofuel production over the next couple of decades. Over 33.5 millions acres are currently enrolled in the USDA program called CRP (Conservation Reserve Program), which pays farmers an annual rental rate for retiring land from crop production and planting it to wildlife cover. CRP contracts typically tie up the land for 10 to 15 years.

Currently, CRP land management is governed by contract stipulations that prohibit disturbance during the breeding season, and encourage wildlife use of the acreage. Many studies have shown that CRP land is vital to sustaining grassland bird populations. Pollinating insects, reptiles and amphibians, and other fauna benefit from these habitats as well.

According to USDA figures, almost 60% of the current active acreage in CRP will see contracts expire by the end of 2013. With the signing of the 2008 Food Conservation and Energy Act (aka the Farm Bill) the CRP cap (maximum acreage to be enrolled in CRP) was already reduced from 39.2 million acres to 32 million acres beginning in 2010. Thus a mandated net loss of over 4% of current active CRP acreage is already slated to occur in the near future.

While some of the expiring contracts will be renewed under the new acreage cap, if prices for biofuel commodities rise high enough, a large amount of CRP land may be lost when owners decide not renew, but to seek “greener pastures” in switchgrass or corn production for biofuel. A mass exodus of from the CRP program would be a disaster for conservation of grassland species in North America. In addition, there is the possibility that the USDA could change the rules for CRP contracts at some point in the future to allow switchgrass production on CRP lands.

Over at the Biofuels and Bio-based Carbon Mitigation Blog of the School of Natural Resources and Environment at the University of Michigan, Kristen Johnson wrote a great post discussing the potential magnitude of the conversion of CRP lands to switchgrass production for cellulosic biofuel. She states that acres currently in corn are unlikely to be converted to switchgrass, since EPA guidelines call for a continued increase in corn-based ethanol production in the near future.

As long as the prices of other commodities like soybeans are high, that leaves only pastureland, hay production land, and CRP land as prime targets for conversion to biofuels. Compared to cropland, these land uses are all of much higher value to wildlife.

The take-home message here is this: if you value grassland habitats and the wildlife that depends on them, keep an eye on this issue. While the Union of Concerned Scientists letter doesn’t specifically address habitat loss, it does shed light on the emissions consequences of biofuel production, and is a step toward helping our public agencies recognize that biofuels are not free of collateral damage. You can view the letter at the Union of Concerned Scientists “Take Action” site.