On Earth Day. Managing weeds is a costly and difficult task. Yet their impacts to the environment are high. Herbicides or hoes cost money and the impacts to the environment when weeds grow unchecked are also significant.

The costs of managing invasive species are staggering. For example, it is estimated that the US spends about $128 billion annually managing invasive species. In 2011 just one federal department, the Department of the Interior (BLM, NPS, FWS, among others), spent $100 million removing invasive species. In the US, herbicide sales are over $5 billion a year, not to mention costs of application equipment, maintenance and labor.

In California over 5 million pounds (of active ingredient) of glyphosate are applied to crops each year. These applications cost farmers and growers hundreds of millions of dollars a year just to remove weeds. Some single weeds have spectacularly high costs. In Southern California eradicating the invasive seaweed, Caulerpa, in Agua Hedionia Lagoon has cost $3.3 million and likely has saved most of the California coast from being invaded as it has been invaded in the Mediterranean and has covered at least 50 square miles. Thus, one could argue the cost of eradication was likely significantly less then the benefits of not having this seaweed.

The costs to the environment due to degradation by invasive species spread are difficult to estimate. Yellow star thistle covers approximately 14 million acres of California and is continuing to spread. If we assume the cost to the environment is similar to the cost of restoring it to its natural state and a low ballpark estimate of restoration costs using conventional methods is $200/ac., then we are looking at an extremely rough cost of $2.8 billion dollars to restore California’s wildlands that are invaded by yellow star thistle. Obviously, the state will not be restoring that many acres, nor spend that much money on invasive species management. The point is that unwanted plants are costly.

The value we receive from natural, un-invaded places are also difficult to estimate. We can agree that ugly, or harmful weeds reduce our desire to go to wild areas. Few people camp in the middle of yellow star thistle fields, the spines on the flowers are too long and sharp.

The costs to rare and unique species are also significant. As far as I know no species had gone extinct due to the introduction of a nonnative plant. Yet population losses of rare plants and animals due to invasive plant infestations are significant and real. In many cases increasing the population of rare organisms means reducing weeds, which can cost hundreds and sometimes even tens of thousands of dollars per acre.

We are so lucky to live in such a beautiful state with so many wonderful places to visit, wonderful foods to eat and so many different habitats for all the unique plants and animals that call California home.