No one in the article claims it is all downside (the shrimp farmer in Georgia now makes his income from Jellyfish) or a claim on the evolutionary advantage of the system. In a direct way, we can trace our own lineage as mammals to being benefited by the extinction of the dominant vertebrate for 160m years in the Cretaceous extinction.

However, in our current position, humans have a different role and relationship with nature: what we do has a direct impact on our environment. Even if you discount the loss of biodiversity as a minor thing to be waved away -- and even if you do take the fairly nihilistic view that all ecosystems are of equal worth -- there are direct impact to humans from our changing of the environment.

In the case of the oceans, they provide a massive economic benefit directly from extraction industries, which have been in decline due to overuse, and mechanisms like the great ocean conveyor belt (http://en.wikipedia.org/wiki/Thermohaline_circulation) transmit tremendous quantities of energy into northern climates providing moderate climates at northern latitudes (particularly, Northern Europe). In the case of corrals, diving, recreational fishing and tourism are key components of many of the economies of nations containing them. Without these natural resources, local economies suffer, as has already happened in a number of Caribbean nations.