Restored Streams Take 25 Years or Longer to Recover!

In northern Sweden during the 1850’s to 1950’s , streams were channelized to help move timber. Boulders were blasted or taken out of the streams. This means that the riparian zones were damaged. Riparian forests are valuable to the fish, because they supply habitat, store carbon, provide shading, and filter water.  

“Northern Sweden is a great study system for determining the results of restoration because of the long history of restoration and the lack of urbanization. Most stream restoration in other parts of the world did not get started until the 1990s. So we have a unique opportunity to study the long-term effects of stream restoration,” says Eliza Maher Hasselquist.

Most streams are typically monitored for five years after the riparian zone is restored. Eliza, the person doing research on riparian zones; count the number of plant species in the streams to count the timeline on how long it would take to be restored. They found that the plants may need to take longer to restore than they thought. It is estimated that the riparian zone may take 25 years or longer to be completely restored.

Eliza says, “The small number of studies of restored streams have often found inconclusive results after stream restoration and this may be because we are too impatient. These ecosystems took thousands of years to develop, and we expect them to return back to their pre-disturbance state in less than five years? We need to be more patient.”

Field picture of stream restored in 1987.
Credit: Eliza Maher Hasselquist

The main objective is to help the fish adapt to the restored surroundings. For that to happen you must leave nature to fix the riparian zones. Seeds are the main ingredient to help support riparian zones. Active seeding of native plants will help the fish, insects, and other creatures repopulate. Planting shrubs could also help jump start the recovery of the riparian zone.

“The Swedish government and the EU are spending millions of crowns every year on stream restoration. We should do everything we can to make sure that we get a good return on that investment. Finding simple ways of improving our methods for restoring streams is important for doing that,” says Eliza Maher Hasselquist.

Here is another link to learn more about Sweden and their restoration findings:

Abmobäcken stream before and after demonstration restoration.
Credit: Daniel Jonsson


Journal Reference:

  1. Eliza Maher Hasselquist, Christer Nilsson, Joakim Hjältén, Dolly Jørgensen, Lovisa Lind, Lina E. Polvi. Time for recovery of riparian plants in restored northern Swedish streams: a chronosequence study. Ecological Applications, 2015; 25 (5): 1373 DOI: 10.1890/14-1102.1
UmeÃ¥ universitet. “Restored streams take 25 years or longer to recover.” ScienceDaily. ScienceDaily, 30 June 2015. <>.

Leave a Reply