Page - 23 - in options, Volume winter 2021

As the global population continues to surge, one of the most complicated challenges facing humanity is securing sustainable food sources. Fisheries not only reduce the abundance of large piscivores such as cod, pollock, and tuna in ecosystems across the world, but also target smaller species like herring, capelin, and sprat that make up piscivores’ diets. A study by Mikko Heino and Ulf Dieckmann, both researchers in the IIASA Advancing Systems Analysis Program, and their colleagues, used a community- dynamics model to explore the effects of harvesting forage fish. Unlike single-species models often used for fisheries assessments, their study accounts for important factors such as individual-level bioenergetics and size structure. On this basis, the researchers have extended and analyzed a dynamic bioenergetic model of the Baltic Sea, in conjunction with historical pattern analysis, to test the effects of fishing for both piscivores and their forage fish. Their findings suggest that piscivores benefit from forage-fish harvesting when the fishing pressure on piscivores is high. “It is true that we must avoid the overfishing of forage fish,” explain Heino and Dieckmann. “However, our findings show that reducing fishing pressures on forage fish may have unwanted negative side effects on piscivores. In fact, decreasing forage-fish exploitation could lead to declines, or even collapses, of piscivore stocks. We must keep this in mind as we manage the exploitation of fish stocks around the globe.” Reindeer husbandry is a traditional livelihood for many indigenous Saami and Finnish people in northern Finland, where it provides a vast array of social, cultural, and economic benefits. The modern-day pressures of climate change, economic development, and competing forms of land-use, however, are posing challenges to the integrity of the reindeer management system. There are various public authorities that steer reindeer management through the changing times. Even though reindeer herders are the central actors in the system, they are often not able to influence the policies pertaining to their livelihood. To help manage future environmental conflicts, in a recent IIASA collaboration, researchers surveyed how herders perceive the drivers of change in reindeer management, along with how these perceptions vary with the diverse land-use and climate patterns found in different herding regions. The crucial factors for most herders were those that directly affected the welfare of reindeer and calving success, such as the amount of ice on pastures or the presence of other land-use forms that influence reindeer foraging and the daily work of herders due to the fragmentation of pastures. Herders had varying or polarized opinions on other factors, showcasing the regional differences in reindeer management. “Awareness of reindeer management is low on the governance level. With this study we hope that local voices will be better heard and included in future policy decisions,” says Mia Landauer, a researcher at IIASA and the Arctic Centre at the University of Lapland. Supporting sustainable reindeer management in Finland E UROP E Analyzing the dynamics of fisheries in the Baltic Sea Regional impacts Mia Landauer: landauem@iiasa.ac.at Ulf Dieckmann: dieckmann@iiasa.ac.at Further info: pure.iiasa.ac.at/17311 Further info: pure.iiasa.ac.at/17024 Mikko Heino: heino@iiasa.ac.at By Jeremy Summers By Fanni-Daniela Szakal Figure: State and privately owned land used for forestry and the present and planned land-use projects in the reindeer management area (RMA; regions with high predator density in the northern area and close to the eastern border, or agricultural regions in the southern area not shown). 23Optionswww.iiasa.ac.at Winter 2021