Someone told me that once, that marshes and wetlands really had no value. No value.
Much of our history on prairie landscapes involved "reclaiming" wetlands. In the context of that mindset, a synonym for "reclaiming" was "destroying."
In reality, marshes, bogs, and fens are unique forms of wetlands that support a lot of life in the form of both animals and plants. They provide habitat for living things. Ultimately, whether you can name the species or describe the interrelationships, you depend on that life. You're in that same web of life, or less poetically and more practically, your life exists in the context of a set of relationships that's broader, deeper and more complex than you're aware of most of the time. And the only way out of those relationships is to forego your own life.
Wetlands are also remarkable for their capacity to clean water.
Every living thing depends on fresh air, potable water, wholesome food. This isn't a surprise or an anomaly. The most basic ethical consideration we can hold is the willingness, and more, the resolve, to preserve the air, land and water for living things. It is deeply within our physical and moral interests to do so.
And yet more... they are beautiful!