Natural ecosystems as a source of ideas
This week I want to share some thoughts on â€śecosystem servicesâ€?, starting with this recent paper:
Proximity to forest edge does not affect crop production despite pollen limitation
They found that the closer grapefruit trees were to forest edges, the more visits they got from pollinating bees, but this trend had no effect on fruit production. Thereâ€™s more to the paper than that, but I want to commend the authors for actually measuring effects on yield. Itâ€™s surprisingly common to measure variables that are hypothesized to have some effect on yield, without measuring yield itself. For example, Risch et al. noted that, out of 150 studies on how intercropping affects insect pests, only 19 bothered to measure yield, and only one study determined how much the pests actually affected yield (Environ. Entomol. 12:625). This would be like medical researchers measuring the effect of some treatment on cholesterol but not checking whether there was any effect on the frequency of heart attacks.
â€śEcosystem servicesâ€? have been a hot topic since Constanza et al. published a paper on the topic ten years ago (Nature 387:253). They estimated that nature provides services (pollination, purifying water, etc.) worth $33 trillion per year, exceeding the value of human economic activity. As an argument for conserving nature, it made me wonder how many of those services are or could be provided by managed ecosystems (including properly managed farms), and how many are provided by species that we couldnâ€™t get rid of if we tried (microbes that break down crop residues, for example). Since then, the ecosystem services meme has spread so much that we rarely hear about all the other reasons to preserve wild species and natural ecosystems. One notable exception is a recent paper by D.J. McCauley titled â€śSelling out natureâ€? (Nature 443:27).
McCauley illustrated the risks of tying nature conservation so closely to ecosystem services by updating an earlier story about the value of wild pollinators to coffee production. The earlier story had valued that service at $60,000 per year (PNAS 101:12579) -- but then the farm in question replaced coffee with pineapple, which doesnâ€™t need pollinators. By the logic of ecosystem services, â€śthe monetary value of the pollinators in forest fragments around Finca Santa Fe dropped from $60,000 per year to zero.â€? But, McCauley pointed out, thatâ€™s only if we assume that ecosystem services are the only reason to conserve nature.
Hereâ€™s something to think about: how does the value of a wild species depend on its rarity? The last 100 orchids clinging to a cliff on Kauai arenâ€™t producing much oxygen. Should we concentrate on protecting spruce trees and oceanic plankton instead? From an ecological perspective, this might make sense. Sure, the spruce trees and plankton are less endangered, but their contribution to ecosystem services is so much greater. Maybe the orchids are essential to some rare insect, but what is that insect doing for the ozone layer?
An evolutionary perspective leads to a different conclusion. Even a rare species may have the solution to important problems. It certainly has the solution to many of its own problems, but perhaps to some of ours as well. For example, certain wild potatoes release insect alarm pheromones when wounded (Nature 302:608), scaring pests away rather than killing them with toxins. Any insect that evolves â€śresistanceâ€? to that signal will also evolve resistance to mating. Some fish see in muddy water by comparing light polarized in different directions, a technique since copied by human engineers (Optics Letters 20:608). Similarly, conch shells have inspired new fracture-resistant materials (Nature 405:1036). A search for â€śbiomimeticsâ€? will find other examples.
Would humans have thought of these ideas, eventually? Maybe. But if I were in charge of an â€śindustrial espionageâ€? program, I would spy on nature rather than on my competitors. Many of evolution's "inventions", coded in the DNA of wild species, would be difficult or impossible to decipher outside of their biological context. Common species are not usually endangered and rare species usually contribute less to ecosystem services essential to humans. But even rare species, and the ecosystems where they live, may be a source of ideas useful in agriculture, engineering, or medicine â€“ ideas whose economic value may vastly exceed that from turning a bit of rainforest into a soybean farm.
Here are some additional papers of note this week: