Maybe you don’t have a pond. I don’t. But pond maintenance can remind non-pond owners and pond owners alike of some valuable ecological lessons.
I was recently having a conversation with the retired president of a multi-national agricultural organization. I asked him about his plans for the coming week. He said he was going to be cleaning out his small landscape pond.
“There is about two inches of crud in the bottom,” he said. “We never realized that keeping a pond would require so much maintenance.”
I replied, “Doctor, it’s hard for me to say this to you, but in my columns, I am always reminding people that in nature, there is no such thing as bare ground. Maybe we also need to realize that in nature, there is also no such thing as clear, standing water.”
In biology, succession is the rule of life. The easiest way to think of succession is colonization. If you had a load of topsoil dumped out back last spring, but time got the better of you, it’s now covered with plants. Soon there will be trees. It’s no different with water. Succession means that new lakes eventually become old ponds, and old ponds become marshes.
A more specific term to describe this process in ponds is “eutrophication.” This literally means “good eating.” In other words, the water begins to hold more nutrients which in turn fills out the food web of producers, herbivores, and carnivores: predators and prey. More nutrients and more eaters equal cloudy water. And “crud” on the bottom.
The problem is that human eyes look too fast to see. We have seen the same field, woods and pond for years. Not much has changed. But the field has been cut for hay each year, the original paths through the woods have become impassible with trees falling down and brambles popping up, and along the dock there used to be a sandy beach in the pond. With time-lapse photography, we would see movement, change, colonization.
In a pond, through time, the amount of light, oxygen and nutrients are related. More nutrients sometimes means more oxygen is used than produced. More nutrients might also mean more shade, either due to cloudy water (filled with microscopic creatures) or dense vegetation. Less oxygen and light usually means less-desirable water and a less-desirable pond.
It’s similar with your lawn: Remember how nice the lawn was before the trees grew up and shaded it? Also, nitrogen similarly greens both your pond and your plants. And nutrient-rich crud on a pond floor is called soil in a landscape.
Penn State Extension’s Thomas McCarty says the change back to dry ground is coming, and it’s the pond owner’s job to slow it. In your landscape, the change back to forest is coming, are you trying to slow it?
Joshua Arp is an ISA-certified municipal specialist, Clarks Summit’s municipal arborist and an operator of an organic lawn and landscape maintenance business. Reach him at email@example.com.