I recently read a blog post by the Woodland Trust about how important dead wood, and leaving it in the forest, is for biodiversity. Think about walking through a forest and how many plants, mushrooms, and insects you can see coming out of a dead log- it’s like its own ecosystem! It reminded me of some great papers I read recently (including a couple I cited in my recent scrapes paper) about creating or keeping dead wood in logged forested areas to provide habitat for rare beetles.
Beetles that depend on decaying wood as a food source, either as adult beetles or the larvae, are called saproxylic. Have you ever ripped open a dead and decaying log before and seen a whitish grub hiding underneath? It was most likely a saproxylic beetle larva munching away on the wood. Unfortunately, logging and other wood uses decreases the number rotting logs in the forest, depriving beetles and other species of needed resources and habitat. There are many saproxylic beetles red-listed (considered rare) in Europe (400 in Sweden alone!). We have a lot of these beetles in the US but not too many are listed as endangered or threatened, at least federally. However, since logging happens here in the US too, we can learn from the European studies and practice their conservation management suggestions just the same.
A paper by Jonsell et al. published in 2004 talks about how man-made tree “stumps” can provide habitat for rare beetles. I put “stumps” in parenthesis because I think of tree stumps as 1-2 feet off the ground but these were actually 15 feet tall! The researchers compared the number and types of beetle species using the created “stumps” to the beetles found in naturally dead stumps. The created stumps had about the same number of beetle species as the natural stumps but half (5 as opposed to 10) the number of rare saproxylic beetles. The researchers also showed that older stumps had more rare beetles, suggesting their created “stumps” just need some more time to rot to be attractive houses for the rare beetles.
In conclusion, we should leave dead trees as a resource for other species, otherwise we’ll have to create dead trees to save species from extinction! This and studies like it also serve to remind us how important it is to remember that sometimes what seems like just left over “litter” to us can be a vital resource to another species.