Raspberries, Birds and Ecosystem Services

A recent article on the definition of ecosystem services sparked quite a debate among its commentators. There seemed to be disagreement on exactly what it truly means: some definitions are quite simplistic (e.g. claiming a simple resource, such as iron, fits the bill); others see it only from a human perspective. At the same time, some respondents applied ethics,  tying it up with human conservation management/engineering. Personally I found many of the arguments disturbing, considering they were coming (supposedly) from educated people in the scientific realm. But, then, sometimes it seems that scientists can suffer from tunnel vision due to specialization. Being a student of both environmental science and ecology requires a more comprehensive view of this world encompassing many of the sciences out there.

In my work, students are taught that an ecosystem service is a “network” of behaviors and or processes that, combined, provide important, if not necessary, functions for an ecosystem. It’s simplistic but since there are numerous such processes in place, it’s best to start humbly and get more detailed with specific examples. Can we humans benefit from ecosystem services? Certainly! But it is important to remember that such processes were in place billions of years before mammals were abiding on Earth, much less Homo sapiens, and do not function merely for human purposes.

Birds provide an excellent example of ecosystem services at work. While most of us are always conscious of their existence, the benefits they provide directly to ecosystems (and as a byproduct, to humans), is often overlooked. The simple pleasure of harvesting wild black raspberries this past weekend reminded me of yet another benefit provided by our avian friends.

Fourteen years ago I purchased my current home and property. It had two habitats, half for human use (house, lawn, neat rows of conifers, etc.) and a “wild” half, mostly left intact simply because it is too wet to be of much human use, although it was once a grazing field for Black Angus raised by the neighbors. By the time I moved in, the Angus were long gone and since then the wet meadow has increased in size while still leaving a substantial human habitat of ~1/3 acre.

One aspect of yard work I’ve always despised is the idea of trimming beneath trees so that lawn (or mulch) goes right up to the trunk. My philosophy is to mow as close as you can and let the rest be. And in areas for which there are no plans to garden or walk about much, leaves, twigs and what-not are allowed to drop and decay. This non-practice creates the conditions that alone allow to go forth the ecosystem service provided by trees, insects, decomposers and detritivores – adding important nutrients and creating more soil. And in these areas where soil supplementation is allowed to take place, the birds step in and add another.

After about 3 years on the property, I was investigating one of these spots where daffodils had been naturalizing. A sharp scratch on the arm confirmed the new presence of wild raspberries. When I excitedly shared the news with the family, they asked when I planted them. “I didn’t – the birds did”, I replied. The queer look on their faces made clear that an explanation was in order. A simple bulleted list told the story:

  • Birds eat wild raspberries
  • Birds fly off to other locations
  • Birds sit in trees
  • Birds defecate
  • Raspberry seeds are eliminated whole in bird droppings
  • Some seeds germinate and take root in the soil beneath the trees
  • Raspberry plants grow
  • Birds eat more raspberries and, now, so do we
wild black raspberries

First harvest of wild black raspberries (Rubus occidentalis) – 2 pounds and counting with plenty left for the Gray Catbirds!

Birds are among many animals that provide the ecosystem service of seed dispersal. Plants are all about reproduction and through evolutionary processes, numerous vectors of seed dispersal have come about. One such method includes plants putting enormous stores of energy into fruit production. This serves only to entice other creatures to eat it, taking the seed away from the parent potentially to be germinated.  Other vectors include wind, rain, burrs, etc., but fruit production provides such a far-reaching and overlapping service to an ecosystem by also provisioning food.

And those who eat the food are part of the entire process. So, GASP, even humans can be naturally implicit in an ecosystem service. Who would’ve thought!