Submitted via IRC for chromas
When yesterday's agriculture feeds today's water pollution
A study led by researchers at Université de Montréal quantifies for the first time the maximum amount of nutrients – specifically, phosphorus – that can accumulate in a watershed before additional pollution is discharged into downriver ecosystems. That average threshold amount is 2.1 tonnes per square kilometre of land, the researchers estimate in their study published today in Nature Geoscience. "Beyond this, further phosphorus inputs to watersheds cause a significant acceleration of (phosphorus) loss in runoff."
[...] Focusing on 23 watersheds feeding the St. Lawrence River in Quebec, the researchers reconstructed historic land-use practices in order to calculate how much phosphorus has accumulated on the land over the past century. The two main sources of phosphorus to watersheds, the land adjacent to tributaries, come from agriculture (fertilizers and animal manure) and from the human population (through food needs and sewage).
Using Quebec government data, the researchers matched the estimated accumulation with phosphorus concentrations measured in the water for the last 26 years. Since the watersheds they studied had different histories – some had been used intensively for agriculture for decades whereas others were forested and pristine – this method allowed the researchers to establish a gradient of different phosphorus accumulations among sites. In so doing, they were able to see at what point the watershed "tipped" or reached a threshold and began to leak considerably more phosphorus into the water.
"Think of the land as a sponge," Maranger said. "After a while, sponges that absorb too much water will leak. In the case of phosphorus, the land absorbs it year after year after year, and after a while, its retention capacity is reduced. At that point historical phosphorus inputs contribute more to what reaches our water."
Low buffering capacity and slow recovery of anthropogenic phosphorus pollution in watersheds (DOI: 10.1038/s41561-018-0238-x) (DX)
(Score: 4, Interesting) by aclarke on Monday October 15 2018, @01:07PM (2 children)
My parents put a pond on their farm in Ontario in the 1960s before I was born. As a kid, we swam in the pond every summer. By the 1990s the pond was becoming covered with algae and the water was no longer clear due to agricultural runoff.
We bought a farm a few years ago. It has a pond on it that we dare not swim in. Due to farm runoff (fertilizer, manure), the water is brown and eutrophic as described in the article. We plan to put an aeration system in. We looked at a windmill but we'll probably go with an electric air pump. The real answer though is changing the farm practices on the watershed. Fortunately for us we control all the land upstream of the pond on the watershed, so for us it's a question of continuing to learn how to farm better, and working with our farming tenant to change practices. And to accept the short-term decrease in profits we might get, that in turn affects how we pay the mortgage.
This spring we planted a couple thousand more trees, and next year we might convert a bunch of farmland to treed pasture. Most of the commercial farmers around here are concerned about their land, but they're more concerned about making a profit. And like most Canadians, the five year plan completely overwhelms the hundred year plan, or rather there is no hundred year plan.
(Score: 4, Funny) by bob_super on Monday October 15 2018, @05:01PM (1 child)
The nice thing about eutrophic is nothing will nibble at your toes, and you could open a spa and convince people the pond is what their skin craves (the smellier, the better).
The nice thing about Canadians is you're complaining that people do have a 5-year plan.
(Score: 0) by Anonymous Coward on Tuesday October 16 2018, @06:06PM
Sorry if I sounded like I was bragging about Canadians.
(Score: 1, Informative) by Anonymous Coward on Monday October 15 2018, @02:10PM
Click the article and found this summary
"Water quality is threatened by a long history of fertilizer use on land, Montreal scientists find in new study."
Which is really old news