Coastal Management

The intersecting issues of climate change and human-wildlife conflict

Samhouri, J. F., Feist, B. E., Fisher, M. C., Liu, O., Woodman, S. M., Abrahms, B., Forney, K. A., Hazen, E. L., Lawson, D., Redfern, J., Saez, L. E. (2021). Marine heatwave challenges solutions to human-wildlife conflict. Proc. R. Soc. B, 299(1964). https://doi.org/10.1098/rspb.2021.1607.

How does an extreme marine heatwave cause human-wildlife conflict?

Extreme climate events are becoming more common and more intense due to the effects of climate change. Although the ecological impacts of many extreme events have been well-documented, less research has focused on the societal and economic impacts of extreme climate events. Human lives are thoroughly intertwined with the natural world. Climate change is not just about changing temperatures and rising seas – it is also about how those impacts extend into human lives and societies.

A recent study completed in collaboration between the National Oceanic and Atmospheric Administration (NOAA) and the University of Washington examined a record-breaking marine heatwave event that occurred in the Northeast Pacific Ocean over 2014-2016. This study focused specifically on how this extreme event exacerbated human-wildlife conflicts and reduced the effectiveness of management and policy interventions that are meant to provide solutions that benefit both conservation goals and human activities.

A humpback whale entangled in fishing gear. This species frequently feeds off the west coast and usually stays out of the way of fishing gear. However, the 2014-2016 marine heatwave caused them to move closer to shore to find food, leading to greater overlap with fishing grounds. Photo: NOAA, public domain.

The human-wildlife impact they chose to examine was blue and humpback whale entanglement in fishing gear and revenue to the California Dungeness crab fishery. The researchers used whale distribution and fishing grounds distribution to evaluate the risk of whales becoming entangled in fishing gear. During the heatwave, whales moved closer to shore to feed, which caused greater overlap between whale habitat and crab fishing grounds. The researchers then simulated the changes in entanglement risk and fishery revenue that would result from several human-wildlife conflict mitigation scenarios utilized by fishery managers. For example, delayed opening of the spring fishing season is meant to lower the risk of whale entanglement, thereby mitigating the occurrence human-wildlife conflict. However, a delayed spring opening also means lower fishery revenue.

Using a model, these human-wildlife conflict mitigation scenarios were applied to 10 fishing seasons between 2009-2019 so that their effectiveness before and after the heatwave could be compared to their effectiveness during the heatwave. The researchers used this study design because they expected the heatwave to shift whale distributions from their normal range, which could impact how well the conflict mitigation scenarios work.

So, how well did the human-wildlife conflict mitigation strategies work?

The researchers found that during the heatwave there was more than double the usual amount of blue and humpback whales within the fishing grounds. After the heatwave ended, a lower occurrence of blue and humpback whales resumed. At the same time, Dungeness crab fishing activity also increased. When the researchers combined data on whale distribution with data on the locations of over 400,000 fishing vessels, they found that because whale distribution overlapped with fishing vessels, the risk of whale entanglement rose in 2015 and peaked in 2016 at over nine times the usual risk. Entanglement risk remained higher than normal through 2018 before decreasing again in 2019.

The researchers then applied the human-wildlife conflict mitigation scenarios to their model and found that the interventions tested were generally less cost-effective during the heatwave compared to the pre- and post-heatwave periods. For example, they found that some scenarios reduced predicted whale entanglement risk twice as much during the heatwave than before it. This means that the management interventions were more effective at preventing whale entanglement during the heatwave. However, under the same scenarios, the expected revenue loss of the fishery industry escalated disproportionately – revenue was four times lower during the heatwave compared to pre- and post-heatwave periods. So the conflict-mitigation scenarios worked to reduce entanglement, but had greater negative effects on the fishery. Generally, these findings suggest that marine heatwaves cause trade-offs between entanglement risk and fishery revenue to become more severe.

Dungeness crab fisherman sorting crabs. Photo: NOAA, public domain.

How can this research inform best practices in a changing world?

This study has important messages for how fishery managers go about maintaining revenue while remaining conscience of impacts to wildlife. As extreme climate events become a more regular occurrence, balanced strategies for dealing with the impacts to both wildlife and society must be developed. These findings can also apply to other sorts of conflicts, such as those that could arise due to the development of offshore renewable energy and aquaculture.

The authors of this study suggest that the development of incentives designed to encourage conservation and mitigate economic loss will be the best way to manage the trade-offs that will arise during human-wildlife conflicts. For example, fisheries can receive payments for reducing fishing extent and duration during an extreme climate event so that we can lower the risk of whale entanglement while also avoiding extreme negative impacts on fisheries. The authors also emphasize the need for the development of tools that can anticipate changing conditions further in advance so that plans can be developed before the extreme event hits. These tools can be combined with “adaptive management” strategies that allow for quick evaluation of both human systems (such as fisheries) and wildlife while the extreme event is occurring.

Cover photo: The Dungeness crab fishery in action. NOAA, public domain.

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