Thursday, October 09, 2008

Chester Springs Marsh - Then and Now

Chester Springs Marsh as viewed looking south from the Bloor Viaduct, about 1996

Chester Springs Marsh, 2008

Picture comparison: the mowed grass is completely replaced by trees and shrubs with some bits of meadow in between. A path circling the wetland is now totally obscured. The only indication of it now is a garbage can placed at the northern entrance point (top end of the graffiti). The red tinged sumac grove in the lower right of the picture is still there although there is a patch missing from the middle. This was created by a homeless encampment which was recently abandoned.

It's been 12 years since the Task Force to Bring Back the Don created a new wetland in the Lower Don. Chester Springs Marsh was the first major project of the Task Force and it has influenced restoration efforts in the Don Valley ever since. As you can see from the original photo, it was built in a former grassy meadow with just a few large trees and some shrubs along the river bank. The photo also shows a few saplings new planted.

Today those saplings have grown to heights of 10m and have turned the grassy meadow into a forest. The marsh is now totally obscured by these trees as the new photo shows. The reality is that the marsh now contains very little water and the area is now more of a wet meadow. Shrubs are starting to encroach on this space and the wetland that it started out to be is fast disappearing.

How did this happen? There are a number of reasons for this some of which were not foreseen in the original design. The marsh was meant to have continual water which would be topped up periodically by high water from river floods. However the channel that connected the marsh to the river quickly silted up so that the refresh now only occurs during extreme high water events. This means that any water that gets in likely dries up before the next refresh.

Another problem was what was underneath. The marsh was built on a former landfill and its excavation exposed some of the rubbish buried there. Some it was stuff like old pieces of pottery and other turn of the century knickknacks. When people discovered this, a flock of scavengers descended on the site digging pits looking for buried treasures. This activity inadvertently created wells which drained the marsh.

So rather than a marsh we have more a meadow that gets occasionally inundated. This is not necessarily a bad thing but there are other issues with the marsh. One of them is the problem of non-native species that have invaded the site. These include garlic mustard, dog-strangling vine, Japanese knotweed, creeping thistle, and teasel to name a few. These plants are starting to dominate the understorey and are crowding out native plants. There are some non-native trees including Siberian elm, black locust and Manitoba maple but they are not yet crowding out the native trees. The native trees are doing quite well and they include a couple of uncommon species such as hackberry and red mulberry.

CSM as viewed from the side. The wetland is no longer visible. Small trees such as willows and shrubs such as dogwood are no encroaching on the area formerly occupied by the pond.

What is the future for the marsh? That is still up in the air. The Task Force has requested a study be performed on the marsh but they are taking their time. The results of the study could recommend that nothing be done or that some level of management or remediation be performed. Whenever that study is completed, I'll let you know the results.


Anonymous said...

Hackberry is not native here, and I expect the mulberry you noted was white not red.

Donwatcher said...

All the print (Farrar, Kershaw) and online ( sources I use show that hackberry (Celtis occidentalis) is native to southern Ontario including the entire northern shore of Lake Ontario. As for the mulberry, that was a guess but since Chester Springs Marsh is a restoration site, I presumed that it was planted here as a native. Think positive!

Anonymous said...

Hackberry is definetly native to southern Ontario.

Anonymous said...

The failure to achieve a proper functioning wetland here is disappointing; but it must be said the site is still drastically improved from its previous state.

Now, if we could just do the areas to the north, including the the 2 snow dumps (Bayview and Sun Valley)....