June 29, 2015

Thoughts on biodiversity

My last post was a celebration of the rich native biodiversity found in the forests of southern Ohio which we experienced at the third annual Mothapalooza event. Our two keynote speakers, David Wagner and Doug Tallamy, were great fun to be with but their messages were sobering. So this post won't have many pretty pictures because, quite frankly, the big picture isn't pretty at all.

We are losing native species of plants and animals at an alarming rate. In his book Bringing Nature Home, Tallamy cites studies that show that we have lost an average of 1% of our native migratory birds annually since 1966. That is nearly a 50% reduction in the population of many of our bird species in the past 50 years.

The drastic decline of monarch butterflies in recent years has gotten a lot of attention, but other insects have fared just as badly. Why do we need to care? We need to care for many reasons and here are a few.

The decline of native insects is directly related to habitat loss, which is basically the loss of the plant communities upon which they depend. Native insects have evolved along with native plants, and many can only survive on those particular species. When we lose the plants, we lose the insects.

Human lives are inextricably tied to healthy plant communities, even though we generally ignore this fact. Plants produce the oxygen that we breathe. Healthy forests filter the water that we need to survive. Insects that feed on the plants are necessary to pollinate many of the food crops that we rely on for survival. Recent studies have even shown that spending 15 minutes in a natural area lowers stress levels and improves blood pressure better than drugs or psychotherapy!

Many of you that are reading this blog enjoy feeding birds in your yard, and spend a fair amount of money on birdseed. But without insects, birds can't survive. Seeds have lots of carbohydrates and some fats, but little protein, and protein is necessary for building animal tissue. Baby birds need protein, which comes to them in mostly in the form of caterpillars that their parents forage for and bring to them. If they have to go far and wide to find those insects, the energy cost will be too great and the nest will likely fail.

Most caterpillars are specialists. In other words, they need particular plant species upon which to feed. Compatible biochemistry is necessary, and only is found in those insect and plant species that have evolved together over time. So filling your yard with gingko, Bradford pear and other alien species isn't going to do much good, from a biological standpoint.

Not only have we destroyed native habitat in order to develop our cities and suburbs, we have introduced all sorts of plant and animal species that have, in many cases, overwhelmed, eaten, and/or crowded out the native plants and insects that are so essential. Kudzu, Japanese honeysuckle, and autumn olive are just a few examples, and then there are the European starlings and house sparrows whose populations have increased enormously since their introduction. The emerald ash borer, an Asian species, has destroyed billions of ash trees, which supported many native insects, and has cost homeowners and municipalities an enormous amount of money.

Recently, we were at a natural area and saw a brown marmorated stink bug (that alien brown critter that finds its way into our houses) sucking the life out of a monarch caterpillar.

I could cite many more examples, but at this point readers may be thinking I get it, so what can we do about it? Unfortunately, parks and preserves are not adequate to halt the precipitous decline of native species (and they are struggling with the influx of aliens). Here are some suggestions from Doug Tallamy and Dave Wagner:

Plant native species in your yard! You don't have to get rid of all your hostas and daffodils, but include some native trees, shrubs and perennials in your landscaping. If you have room, plant some big native trees like oaks, maples, hickories and hackberries. Include both nectar plants for insects and caterpillar food plants. Doug's book offers lots of suggestions about plants that are suitable in various regions of the country. 

We have started to convert most of our landscaping to natives, but I still have my hostas and Endless Summer Hydrangea that I got years ago from a friend. They are basically biological deserts, but I have a lot of other plants that are beginning to attract pollinators and other insects. Suburban lots can be essential for maintaining the native biodiversity that is so important. But walk into any garden center and you won't see many native bugs because all they are selling are alien plants that have no value for our native insects. Seek out and support native plant nurseries in your area.

Preserve habitat! Buy land, especially forests, if you have the means, and join and actively support organizations that preserve and rehabilitate natural areas.

Minimize or eliminate the use of lawn chemicals! Dandelions and clover never hurt anyone. Clover is a wonderful nectar source for all sorts of insects, but is killed by lawn herbicides. Excessive fertilizer runoff is a real threat to our water supplies.

Vote for people who understand and appreciate good science! This is a lot more important to our survival as a species than how they look on TV or what they did in college 30 years ago.

The situation isn't hopeless, but we are getting close to that point. So at least plant some natives in your yard and encourage your city to do the same in parks and street rights of way. Neighbors--stop by any time and walk around our back yard to see how it evolves since we have planted spicebush, native viburnums, shrub dogwoods, wild hydrangea, cedars and many others. Look at what's coming up in our rain gardens, which divert runoff from our downspouts into basins where it can sink into the ground to recharge groundwater and lower stormwater runoff, a whole other topic that I haven't mentioned! Here are a few pictures of some of the native plants in our yard:

Orange Milkweed and Blue Vervain
Redbud, elderberry, purple coneflower starting to bloom, rattlesnake master, and wild hydrangea.

Closeup of wild hydrangea--these have been great and have attracted all
sorts of pollinators
Endless Summer Hydrangea--all flowers are sterile and not much seems
to eat the leaves so it really has no
biological value. It has sentimental value though, so I'm keeping it!

Purple coneflower

1 comment:

  1. A strong, clear essay with a call to action. I want all my FB friends to read it and I hope it spreads a lot further than that. You defined the problem and offered part of a solution, a solution involving a new relationship with our natural environment. Thank you.