Our neglect of invasive plants is locking us in to future consequences that will affect timber, fisheries, agriculture, and recreational industries, particularly the spread of English ivy and holly that will soon be unstoppable in regional forests. This ecological time bomb – horrific for its own sake – is clearly a financial time bomb for our state and economy.
Efforts to restore forests are constantly compromised by re-introductions of invasive seeds from neighboring land, squandering public money.
It took 100 years for ivy to cover 50 percent of Seattle’s urban forests, where English holly and laurel far outnumber native tree sprouts. Holly is doubling every six years, and “has the potential to become a dominant species in both number of individuals and area covered within a few decades… and transform the region’s native forests on a large scale.” (Dr. David Stokes, UW Bothell).
Our experience in urban forests suggests, in another century or two, the complex diversity needed for pollinator, fish, and wildlife habitat will be severely degraded region-wide. This is a state of emergency, with unacceptable consequences. The longer we wait, the more expensive it will be.
We have no rational choice but to motivate stewardship for all land owners and managers – for the sake of regional forests and for Puget Sound.
Mandates for control will be futile for a public resistant to government regulations. More than 90% of those doing restoration work in backyard Environmentally Critical Areas avoid the ECA permits and state SEPA regulations – regulations that can delay restoration and cripple our race against time.
Rather, an incentive approach could address ECA concerns with better outcome than regulations.
My suggestion is an “eco-rating” program that measures environmental attributes as an addendum to property tax assessments. Private, certified assessors would calculate the (positive or negative) values of tree cover, impervious roof/concrete surfaces, stormwater capacity, soil health, invasive species, or any other attribute considered important to the public good.
This eco-rating, easily applied by county assessors, could earn property tax breaks for individual owners, and collective tax breaks, where everyone in an eco-district could receive a nominal deduction for collectively increasing tree cover, for example (tempering the demand for views), or for eradicating knotweed in a watershed (an invasive plant extremely harmful to salmon habitat).
Property tax breaks are currently not possible given the State’s “Uniformity Clause” constitutionally preventing variable property taxes. Changing this clause is critically important to motivating other public goods, like incentivizing density solutions in urban villages, or rewarding emergency preparedness – a public safety issue.
This eco-rating may be similar to King County’s “PBRS” Public Benefit Rating System, which only applies to larger, usually farm properties or a cooperative of smaller properties. The regulations are burdensome, enrolling only a hundred or so properties a year. Seattle Public Utilities (SPU) has a “Stormwater Facilities Credit,” but no one knows about it. The RainWise program has a one-time rebate for rain gardens, barely covering the cost and paperwork for installation.
An eco-rating would be optional, simpler, and educational for landowners wanting to better manage their land.
If property tax breaks are out of the question, I would suggest that King Conservation District (KCD), SPU, and King County partner to combine KCD fees, stormwater fees, and wastewater fees to create larger annual, repeating incentives for landowners so that restoration investments pay off. Unlike taxes, fees can legally be adjusted. Fee breaks would also need to be balanced with fee increases, at least an Invasive Species fee on land that harbors invasive seed sources, and fees on invasive plants that nurseries continue to sell. One could argue that fee hikes may not be necessary if private stormwater improvements made government mitigation projects unnecessary.
Recognizing the gravity of the invasive threat is a weakness of the human psyche – incremental changes aren’t noticeable, and we have little experience or appreciation of the severity of distant consequences – we therefore don’t react appropriately until it’s too late. Most citizens would want to do the right thing if given half a chance, and annual incentives may be our best educator and motivator. Not just for homeowners, but for any property manager, whether a municipality, school district, public agency in charge of right-of-ways, or departments of natural resources. This private/public conundrum of invasive seed sources crossing property boundaries is also a weakness of our legal infrastructure – the pretense of boundaries in a system that socializes the costs of our choices. One day, these small, incremental costs of neglect will add up to an effect that will far outweigh the price of prevention.
Following are references for the threat level of holly, one of many invasive plants.
“Holly is proliferating and spreading rapidly at two scales: contiguous, primarily vegetative, expansion of tree clumps, and long distance dispersal via seed. Spread by both mechanisms appears to be accelerating, with population and canopy area both increasing approximately exponentially, with doubling times of approximately 6 and 5 years respectively. Projecting past spread patterns forward suggests that holly has the potential to soon become a prominent species both in number and canopy extent, likely at the expense of native plant diversity and forest structure. Based on these results, we offer recommendations for holly management in forested areas in the region.”
“As one of the few invasive plants apparently able to colonize closed-canopy Pacific Northwest forest (Gray 2005), holly may have the potential to transform the region’s native forests on a large scale.”
“Trees > 10 years old appeared to have very low mortality rates and exhibited accelerating rates of size increase and biomass accumulation with age. Native vegetation was greatly reduced under holly canopy.”
“It is a small-to-medium-sized (up to 23 m (70+ feet) height in its native range [Peterken and Lloyd 1967]) dioecious evergreen tree that can reproduce both vegetatively and from seed.”
“The spread of non-native species is emerging as one of the greatest threats to biodiversity (Wilcove et al. 1998, Primack 2010). Invasive non-natives can have diverse and far-reaching effects on native ecosystems, including the elimination of native species and alteration of physical structure and ecological processes (examples in Lockwood et al. 2007). Invasive plants pose a particularly serious threat to natural areas. …While (holly) is widespread, it appears to still be at a level that is amenable to control. Our future projections suggest that delaying control for even a few years will result in a substantial increase in number of holly trees.”
Pictures of an Invasion: English Holly (Ilex aquifolium) in a Semi-natural Pacific Northwest Forest. David L. Stokes, Elliott D. Church, David M. Cronkright, and Santiago Lopez, University of Washington, Bothell, 18115 Campus Way NE, Box 358530, Bothell, WA 98011-8246 USA