Good can come of a bad aquatic weed

Lakes and ponds support a great many forms of life, including weeds that by definition are invaders. A prime example is Eurasian watermilfoil, a leafy plant can be found in the waters of most states and Canadian provinces.

In the eyes of some people, there’s nothing good about this non-native weed. It spoils a swim, it bothers boaters, it can displace native aquatic plants and it can devalue waterside properties.

Hence, considerable time and money gets spent to poison the stuff or rake it out of local waters.

But a reader of this blog recently pointed out that milfoil’s not entirely a negative. As in Nature and life generally, some bad things can also have good sides. For example, on dry land milfoil can make for a helpful soil amendment, an effective fertilizer or a good mulch.

A blogger in southwestern Wisconsin recently posted a reflection with the colorful headline “Milfoil Mulch: turning crap into crop.” Beyond providing a phosphorus and calcium boost, freshly harvested and still-moist milfoil mulch can help sustain some new plantings through a dry spell.

 Also, a distinct advantage over other mulches and fertilizers is the fact that milfoil doesn’t have seeds – it can’t spread on land as the components of some other composts can.

And, too, in lakes and ponds, milfoil can do good things. Its shady leaves can provide the right amount of light for native aquatic plants that thrive in semi-darkness.  Plus, small fish can find protection from predators in the leafy sub-surface forests.  Finally, milfoil can use up dissolved phosphorous that in other cases could ruin water bodies by feeding growths of algae.

None of this ought to be construed as a celebration of milfoil.  Call it, simply, an illustration that some things that are considered bad in fact have good sides, just as some things that are considered good also have bad sides.

An example of the latter is the use of herbicides to eradicate milfoil; the same chemicals that go after milfoil can also harm native aquatic plants. Likewise mechanical harvesting of milfoil; the machines get the weed out, but they also harvest small bugs that hang out on the weeds that might be part of the local food chain. Better, then, to focus on prevention — by preventing invasive aquatic weeds from getting into local waters in the first place, commonly by stationing volunteer watch-guards at boat-ramps.

Bottom line: In Nature, few things are black and white. That goes for the perceived good, and it also goes for the perceived bad.



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