Selected tags: tipping points

Coral Reef Thresholds for Ecosystem Management

(c) Jim Patterson Photography,

(c) Jim Patterson Photography,

By: Rod Fujita & Kendra Karr

Fisheries management is principally focused on managing fishing pressure, with the goal of keeping individual fish stocks healthy enough to produce good yields.  But fisheries also affect the basic processes that keep ocean ecosystems healthy.  This is why it is important to understand how many fish need to be in the system to maintain the many important services that an ocean ecosystem can produce — including the maintenance of biodiversity, tourism value, and fisheries — and to manage fisheries so that fish populations remain at about that level.

The evidence that fish are important regulators of ecosystem processes is particularly strong in coral reefs.  The abundance and variety of fish is one of the most striking aspects of a healthy coral reef.  Some species transport energy and nutrients between seagrass meadows and the reefs.  Grazing fish species on a healthy coral reef keep seaweeds that would otherwise over-grow the reef in check.   Predators regulate populations of prey species, responding to natural variability by adjusting their feeding rates and numbers.  On a healthy reef, many different species occupy each of these niches, and each does their job in a slightly different way.  This enables the reef to resist threats and other changes (like hurricanes) and to recover from very storms or human impacts, within limits of course. Read More »

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Finding the Ecological Cliff and Staying Away from It: Thresholds for Sustainability

In “The Tipping Point: How Little Things Can Make a Big Difference,” author and journalist, Malcolm Gladwell explains how sociological changes often happen very quickly and unexpectedly.   He describes a tipping point as “the moment of critical mass, the threshold, the boiling point.”

It turns out that many natural ecosystems have tipping points too, called ecological thresholds.  Healthy ocean ecosystems can resist change, exist in alternative states and recover from storms, earthquakes, volcanic eruptions – and even from human activities like pollution and fishing.  Having more than one species that do similar things but in slightly different ways helps ecosystems stay healthy; i.e., makes them resilient.  But when we reduce species so much that they can't play their ecological roles or when we stress the system too much, these ecosystems can reach a tipping point and change rapidly from beautiful, productive systems to damaged systems that are incapable of creating the wonders and benefits they once produced. Read More »

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