City launches war on weeds at Forest Park
For two decades, a slew of volunteers and professionals have hacked away at English ivy, blackberries and other invasive plants engulfing Forest Park, the crown jewel of Portlands park system.
But at best theyve just been holding the line, says Kendra Petersen-Morgan, a natural resource ecologist for Portland Parks & Recreation, as ivy continues choking trees and invasives push out native plants and diminish wildlife habitat.
The problem is we are losing native species diversity, Petersen-Morgan says. Left untouched, its going to spread and infect the rest of the park.
Now the city is embarking on its most ambitious plan of attack yet, a multiyear effort called Restore Forest Park that aims to eliminate invasives entirely from Portlands iconic park, one area at a time.
Starting in mid-August, crews will dig into 155 acres near Balch Creek, on the southern side of Forest Park, funded by a $100,000 Nature in Neighborhoods grant from Metro. Next spring, a second phase will commence on 170 acres on the north side of Forest Park.
The parks bureau, in cooperation with the Forest Park Conservancy, Metro and others, is making Restore Forest Park an early step in a grander campaign called Renew Forest Park, which is projected to take 20 years and cost of at least $20 million. That campaign envisions ecological restoration of the 5,200-acre park as well as a new official park entrance, nature center, wheelchair-accessible trail and viewing platform. The nature center parking lot will accommodate school buses, expanding the use of Forest Park for field trips. The Oregon Legislature recently granted $1.5 million for design and other preliminary work.
While actual construction is not yet scheduled or funded ecological restoration is starting now with the work on invasives.
Forest Parks southern and eastern sides are swamped with English ivy, holly, laurel, clematis and non-native blackberries, Petersen-Morgan says. I call them ecologically damaging weeds.
Not surprisingly, the most infected areas are those that border urbanized areas, the usual entry point for invasives.
Forest Park isnt the only city park riddled by invasives; Mount Tabor Park and others also have been ravaged. But the parks bureaus three full-time staff working on invasives spend more than half their time at Forest Park, focusing on the healthiest sections first, Petersen-Morgan says.
Tried and true methods
The city will use the same techniques as in the past. Crews will dig out invasives by hand in easily accessible areas near hiking trails. On steep or sensitive terrain, state-licensed professionals carrying backpack tanks will use wands to spray herbicides directly on offending plants. Theyll spray a mix of glyphosate and triclopyr. Glyphosate is the main active ingredient in Roundup; triclopyr is an ingredient in Crossbow, two widely available commercial herbicides.
These have been selected because they are biodegradable, they have low toxicity and they do not bioaccumulate or persist, Petersen-Morgan says.
Theres nothing new, says John Reed, who coordinates the Integrated Pest Management Program for Portland Parks & Recreation. The only new thing here is we finally have money set aside in the budget to tackle these things.
Other organizations that manage natural areas, including Metro, The Nature Conservancy and The Audubon Society, use the same herbicides, Reed says.
Parks officials say the herbicides are more practical than trying to dig out weeds by hand throughout Forest Park, and are the safest available chemical mix that will do the trick.
But there is one new wrinkle in the use of glyphosate, the worlds most widely used herbicide.
In March, the International Agency for Research on Cancer, a research arm of the World Health Organization, labeled glyphosate probably carcinogenic to humans.
The U.S. Environmental Protection Agency has launched its own new study of glyphosate; results are expected soon.
It certainly does raise the level of concern about using products like this, especially in public spaces, says Lisa Arkin, executive director of Beyond Toxics, an advocacy group based in Eugene.
Scientific findings on chemicals evolve, Arkin notes, but historically they shift in only one direction raising new concerns about their safety, rather than the other way around.
Jeremy Olsen, assistant director of the Eugene-based Northwest Center for Alternatives to Pesticides, concurs that glyphosate and triclopyr are commonly used by natural resource agencies and have proven to be effective. We dont see it as a black and white issue, he says.
They are totally different from another class of pesticides, neonicotinoids, Olsen says, which have been traced to several mass bee deaths in the Portland area.
The Northwest Center for Alternatives to Pesticides would prefer that the city use manual methods to remove invasives, but understands that may not be feasible at a huge property like Forest Park, says Sharon Selvaggio, the organizations healthy wildlife and water program director, based in Portland.
Only 25 percent of glyphosate is left in the soil after 20 days, she says, and 25 percent of triclopyr is left after 54 days.
The main danger to humans appears to be for farmers and herbicide applicators who use it regularly, and are more likely to get non-Hodgkins lymphoma, a form of cancer, Selvaggio says.
But theres been very little research on combinations of chemicals, Olsen says.
New take on invasives
Tao Orion, a Cottage Grove expert in permaculture, opposes the use of herbicides on public lands, and thinks they should be managed much like organic farms. In addition to the link with non-Hodgkins lymphoma, Orion argues that glyphosate alters the mineral composition of soil, and has been shown to lead to more botulism, tetanus and salmonella in cows and chickens.
Orion, who wrote the new book Beyond the War on Invasive Species, takes issue with public lands managers who think they can go back to some prior period when only native plants flourished.
I would argue theres no going back, she says, and that public land managers need to accept that natural areas evolve.
Reed says the International Agency for Research on Cancer findings were based on old science, and didnt cause him to change his opinion on glyphosate and triclopyr. Since that report came out, he says, the European Union completed a four-year look at glyphosate. They did not find evidence of carcinogenicity, he says.
No pesticides are totally safe, but glyphosate has a low, low, low toxic profile for humans and implications for wildlife, says Dave Stone, a pesticide toxicologist at Oregon State University and director of the National Pesticide Information Center, funded by the EPA.
The International Agency for Research on Cancer evaluates chemicals for their hazardous properties, not based on the actual risk of using them, Stone says.
Stone, who lives in Sellwood, says what the Parks Bureau plans to do in Forest Park is relatively safe, because the application there is very far removed from occupational exposures that cause the most concerns. Glyphosate doesnt cross into human skin or the lungs, he says. The main way humans get exposed is if they eat something with the residue left on the leaves.
The Parks Bureau will keep people out of areas being sprayed until its safe, says Reed, who notes that Portland Parks & Recreation is the nations only parks system certified as Salmon-Safe.
Were leaving ourselves a wide margin of safety, Reed says. Besides, he adds, theres no question that its the invasives causing massive environmental degradation at Forest Park.