What do praying mantises, Public Act 12-155, and the populations of Woodbridge and Orange have to do with the environment in Milford? Clue: H2O.

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Stuck? Let’s do the dots.

1. Woodbridge and Orange are the two towns immediately north of Milford in the watershed of the Wepawaug River. The Wepawaug’s headwaters lie in Woodbridge within “Milford Meadows Swamp and Preserve,” 250 acres of land owned and maintained for public access by the Town of Woodbridge and the Woodbridge Land Trust. Orange is downstream to the south. The populations of Woodbridge/Orange are 8,990/13,956, respectively, with population densities of 478/811 people per square mile.

2. PA 12-155 is an act regulating the use of phosphorus on established lawns. Phosphorus is a major ingredient in fertilizers: It helps plants’ root systems and flowering. Plants only need phosphorus when they’re newly-seeded: Established lawns, for instance, get sufficient phosphorus from grass clippings or mulched leaves.

Nonetheless, many homeowners and even landscapers apply fertilizers containing phosphorus willy-nilly. This might be OK except that when phosphorus gets into any waterbody it spurs algae and their plant kin to grow, hog all the oxygen, turn the surface green, kill fish, and make swimming a nightmare.

So PA 12-155 prohibits the application of lawn fertilizers containing more than a trace of phosphorus unless a soil test shows phosphorus is needed. It also prohibits applying phosphorus fertilizers within 20-15 feet of waterbodies, depending on how they’re spread, while they can’t be spread at all onto impermeable surfaces.

3. Praying mantises are insects whose favorite food is other insects. They hatch their eggs in pods as fat as walnuts: 75 to 200 baby mantises emerge from a pod and do their part in making plants safe from insects just as effectively as any pesticide, while allowing birds and bats their chances, too.

Now you know the dots, it’s easy to connect them. What goes on in Woodbridge doesn’t stay there: It travels down the Wepawaug to Orange, then Milford (population 52,759, density 2,376). If people living upstream don’t over-apply fertilizers containing phosphorus; if they don’t spray pesticides, but instead apply biological controls such as praying mantises (ladybugs work too); and, most important, if Woodbridge and Orange don’t increase their population densities to urban levels, then Milford’s signature river will be clean and healthy when it gets to City Hall.

Milford is lucky. Look at New Haven. Its signature river is the Quinnipiac, whose upper watershed includes Southington, population 43,069, density 1,200.

The Quinnipiac is so polluted that Save the Sound volunteers have recently been sent 22 miles upriver to Southington and are helping residents there plant rain gardens, which, by filtering run-off from impermeable surfaces, produce much the same result as praying mantises and PA 12-155.

Fellow Milfordites — we live as downstream as downstream can be. Let’s give thanks for praying mantises, PA 12-155, and our upstream neighbors in Woodbridge and Orange, with an average population density of only 644.5.