The people cry out for the environment. The government and perhaps avid supporters of “eco-friendly” heed. They instantly set up a policy that can restore a population of California condors over 20 years. A species of sea turtles narrowly avoids extinction because of human endeavors. They have appeased the public of immediate dangers of these charismatic species, and they are happy.
But should they be? We only know of these successes on the scale of individual species. What we do not know is the impact of these conservation efforts on the whole environment. For example, what if the efforts to save one endangered species counteract to destroy another endangered species?
This problem is outlined in a recent article in Conservation Biology. It addresses the current efforts to conserve the two interacting endangered species, the sea otter and the northern abalone, and the importance of protecting both, to preserve the ecological interaction. The importance of species interactions in shaping ecological communities is undisputed. However, listings and recovery activities under endangered species policies continue to focus only on individual species, despite the fact that they are known to interact strongly with other species within the area. Failing to account for these kinds of strong interspecific interactions leads to biased estimates of viability, the setting of unachievable conservation goals, and inefficient use of conservation resources. This article further addresses the allocation of conservation effort over time to recover two interacting species – sea otter and northern abalone. By using simulation-based methods, the study was conducted to discover the feasibility of achieving recovery targets of these two prey-predator species.
It was found that the sea otter population reached 75% of its carrying capacity with occurrence of oil spills in the absence of sea otter removal for all functional responses. When sea otters were removed, the sea otter populations were maintained at 50-70% carrying capacity. When nothing was done to the sea otters, the density of abalone was naturally predicted to decrease.
These results suggest that under current estimates of poaching of northern abalone and recovery of the sea otter population, achieving the set recovery target is highly unlikely without management. In addition, removal of sea otters had only a marginal effect on the abalone population, suggesting that reinforcement of antipoaching measures should be the highest priority if the objective is to achieve the short-term recovery target for the northern abalone. Since historical densities of sea otters and northern abalone are unknown, the effects of extirpation of the otters on the abalones are inconclusive. However, with the predation by sea otters, it was shown that abalone densities fell below 0.23/m2, suggesting that as long as sea otters are present, northern abalone are unlikely to reach densities observed during the pinnacle of the northern abalone fishery.
This study assesses the probability of success of management actions in achieving multiple objectives. It is also a practical way to evaluate the potential success of management actions because it explicitly accounts for a species’ functional response to predation and the uncertainty surrounding the response. In addition, this framework can be used to model the complex trophic interactions between non-native invasive species and native endangered species. Most importantly, this study provides further evidence that failure to account for interactions between species could lead to inefficient management strategies, waste of scarce resources, and at worst species extinction. Any two species can be demonstrated the same way as the sea otter and northern abalone, showing us some hope for improvement of conservation efficiency.
So the message out to the world is this: we cannot only emphasize the protection of a single species, but those around it; any aspect of the niche that the target species fulfills must be accounted for when making conservation decisions. Ignoring this fact will result in dire consequences for the environment, and the original plan with a purpose of saving mother-nature is likely to end up destroying her.
Source: Chades, I., Curtis, J., Martin, T. 2012. Setting Realistic Recovery Targets for Two Interacting Endangered Species, Sea Otter and Northern Abalone. Conservation Biology 26(6):1016-1025