By Sally Brown, University of Washington

Abstracts of these resources are available in the searchable Information Portal offered to Northwest Biosolids members.

  1. Biosolids application increases grasshopper abundance in the short term in a northern Canadian grassland

  2. Effects of biosolids amendments on American Kestrel nest site selection and diet

  3. Wildlife responses to long-term application of biosolids to grasslands in North Carolina

  4. Effect of habitat area and isolation on fragmented animal populations

  5. Grassland compost amendments increase plant production without changing plant communities

There we were at Biofest, our regional conference, on the second day waiting for the last speaker before lunch.  I was sitting next to Maile (Executive Director of Northwest Biosolids) and losing patience with the technical difficulties trying to connect to Karen Hodges from the University of British Columbia.  Her teaching schedule made it impossible for her to attend in person so we were trying to have her show up via a web app.  It wasn’t working.  After a morning listening to speakers talk about contaminants in parts per trillion (Ned Beecher did an excellent job talking about PFAS), I was ready to skip out and get lunch.  Steady as always, Maile gently told me to just give it a minute and boy am I glad she did.  Dr. Hodges presented results on wildlife surveys conducted on a ranch in British Columbia where biosolids from Metro Vancouver have been applied over the years.  She was an excellent speaker and teacher with an excellent story to tell- with no mention of parts per trillion or no stick cookware.

Instead she talked about her observations at the ranch.  The first two papers are from that work and more are on the way.  She and her team observed that the biosolids increased vegetation on the ranch.  That vegetation in turn provided habitat for a wide range of insects who in turn provided food for a wide range of birds.  The take home of the talk was that the biosolids improved the habitat- to the point where not only numbers of the expected critters increased but several sightings of birds on endangered lists were also made.  In other words, the biosolids helped make the site a better place, a more functional habitat.  You can stop reading here and just smile.  If you want a few more details…

The first paper reports Dr. Hodges’ findings on grasshoppers at the site.  They trapped the bugs on sites at the ranch where biosolids had been applied 1-2 years prior to sampling.  These were compared with control sites and sites where the biosolids had been applied the year of sampling.  There were just under 4 times the number of grasshoppers on the biosolids amended sites in comparison to controls or the freshly applied sites.  The bugs caught were similar across all sites on the size of the grasshoppers, as was species and sex.  Hopping ability was not measured.  The authors note that many birds and mammals like to eat grasshoppers and so an increase in their numbers suggests that using biosolids could be an important tool for site restoration.

The second paper, by the same author, takes to the skies.  At the same ranch, the authors studied Kestrels, the smallest raptor in N America.  They found a higher portion of nests in areas where biosolids had been applied and also observed more kestrels in those areas.  The birds fed on voles (would like to have some of those in my garden - the kestrels, not the voles, have plenty of those already) and also on the grasshoppers.  They conclude that the biosolids applications result in higher prey populations, thereby bringing back the raptors.  

The third paper takes us out of beautiful British Columbia and to North Carolina.  Here the authors conducted a broad survey of grasslands +/- biosolids.  The biosolids had been applied annually for 21 years prior to the start of the survey.  The authors found bigger and denser plants, but fewer varieties on the biosolids amended plots with the vegetation dominated by tall fescue.  The control plots supported a wider variety of plants including forbs, but they were significantly smaller.  The birds like the bigger grass and the authors found almost 3x more birds on the biosolids amended plots compared to the control.  Deer populations were the same across the sites.  


The fourth and fifth papers are bonus - waiting for the next papers from Dr. Hodges to come out.  The fourth is an older paper co-authored by Dr. Hodges in PNAS - a very highly thought of journal that has also been highly cited.  It is there if you are really interested in animal populations and the impact of fragmented habitat or if you need proof that this researcher is the real deal.

The final paper talks about the impact of compost on plant species diversity at two sites in California.  If you were concerned about too much grass and loss of plant diversity as described in the third paper, potentially using compost instead of cake is the best approach.  

Take home messages from this library:

  • Listen to Maile
  • Take a break from the ppt to remember the big impacts and benefits of biosolids