Some rivers and lakes have a lot of Duckweed; it can be a serious nuisance.
We are sometimes warned to never let this plant get into natural waterways.
However, most natural bodies of freshwater already have some, and this plant can grow at an enormous rate, so a little bit more of the same type of Duckweed is not likely to make any difference.
Duckweed is Edible Many animals, and a small number of people, eat Duckweed.
It is a very good food for Ducks and several other types of bird as well as for many fish and some Tadpoles.
So why do these not keep it under control? In some cases it is because there are not enough of them.
The birds may have been killed off.
The killing of birds is not necessarily by hunters.
Some hunters are also conservationists who do a lot for the environment of the animal they intend to hunt.
Quite often the reason there are less birds and fish is because of habitat destruction and pollution.
A Polluted Lake Imagine a lake that is surrounded by Human activities including farmland and towns.
The water flowing into the lake from the farmland contains fertilizer residues including Nitrogen and some Phosphorous.
The water from the towns has all sorts of pollution.
This would be even worse if the lake is used for the disposal of partially treated sewage which also has a lot of plant nutrients.
So the Duckweed is in water with a high Nitrogen and other nutrient concentration.
Under these conditions it grows at a ridiculously high rate, so, of course the few remaining Ducks and other Duckweed eating species cannot keep up.
Then People say the lake has a Duckweed problem.
Yes, this lake certainly has problems, but getting rid of the Duckweed will not solve them.