Background

According to one creationist,

the ecosystems needed to support life (as we now see them in this post-Fall world) are incredibly complex and finely balanced. It is not only unreasonable to believe that they could arise by chance, but also totally unreasonable to think that they could survive for millions of years. The longer the time period, the greater the chance of something going amiss, such as: an unstoppable disease spreading; a killer meteor hitting the Earth; massive climate changes; bad mutations accumulating; major imbalances in food supply or nutrient ratios. The possibilities are almost endless about what could go wrong, given the high degree of interdependence of the systems in the living world. (Truman 2001:53)

The short response

1. No evolutionist claims that any ecosystem formed randomly all at once.
2. The natural appearance of new ecosystems has been observed on islands created or sterilized by volcanic activity.
3. Individual ecosystems can indeed be fragile, but when one fails it creates a niche for a new ecosystem to take its place.

The longer response

I. Can ecosystems arise naturally?

The claim that ecosystems are too complex to have arisen “by chance” is bizarre. If the claim is that an ecosystem containing many interdependent species could not have formed randomly all at once, that may be true, but no evolutionist has ever claimed the contrary. If the claim is that an ecosystem cannot come into existence gradually and naturally, through the introduction and coevolution of new species, then creationists must provide good reason to believe this—mere bluster about how “unreasonable” scientists supposedly are, is insufficient. The burden of proof is firmly upon the creationists, especially since islands that were sterilized (such as Krakatau Island and Long Island, Papua New Guinea) or even newly created (such as Anak Krakatau and Motmot) by volcanic activity during human history, have subsequently come to contain new ecosystems. To my knowledge, no sailor has ever photographed the seraphim and cherubim shuttling plants and animals down from Heaven to such islands, though I will confess I have not asked very many.

II. Are ecosystems too fragile to persist naturally?

While it surely is true that ecosystems containing many specialized and interdependent species are fragile, it is difficult to see what problem this is supposed to pose for evolutionary biology. The destruction, in part or whole, of an ecosystem creates opportunities for evolution by opening new niches for organisms. In fact, catastrophic events leading to massive extinction have precipitated some of the most significant evolutionary transitions in the history of life. One example is when cyanobacteria first saturated the atmosphere with oxygen (not necessarily directly—see Benton 2008:39-40): in doing so, they succeeded in poisoning themselves on a worldwide scale, but also created a huge new niche that was exploited by cousins fortunate enough to evolve the ability to utilize oxygen. Another example is the extinction of the dinosaurs at the end of the Cretaceous Period, possibly due to an asteroid impact on the Yucatan Peninsula, which in turn paved the way for the complete takeover of the mammals. We humans owe our existence to events like these, not to the benevolent hand of a deity maintaining a fictitious harmony of nature. Far from revealing something wrong with the scientific history of life, the fragility of complex ecosystems is itself one of the engines of evolution: the rise, transformation, and fall of individual ecosystems does not by any means translate into the fragility of the biosphere as a whole.

References

Benton MJ. 2008. The History of Life: A Very Short Introduction. New York: Oxford University Press.

Truman R. 2001. The fish in the bathtub. Creation 24(1):52-53.