Portfolio planning
Fundamental to portfolio planning is risk diversification, the idea that managers should spread exposure to risk so that declines or losses of a single conservation “asset” will not cascade to the entire focal area or resource. This idea was adapted from the Modern Portfolio Theory (MPT) used in finance (Markowitz 1991), to optimize conservation activity by strategically allocating conservation resources to maximize the expected conservation returns for a given level of uncertainty (Ando & Mallory 2012). Due to uncertainty in species’ and ecosystems’ responses to climate change, managers may choose to maintain a portfolio of genetic, biotic, or geophysical diversity, for example by working to restore the genetic diversity of a population, by maintaining a diverse plant community, or by protecting a landscape with varied topography (Anderson et al., 2015; Webster et al., 2017). Managers could additionally implement a portfolio of different management actions over a landscape scale to reduce risk (Aplet & Mckinley, 2017). Additionally, portfolio planning can integrate into adaptive management by trying different things in different places and learning over time (Allen et al., 2013; Aplet & Mckinley, 2017).
There are multiple ways to approach portfolio planning. At the species level, managers can assess and preserve a portfolio of assets that a species can exploit throughout time and space rather than focusing on preserving optimal resources (Schindler et al., 2015). At a population or community level, managers can create a portfolio plan to ensure species are distributed across a gradient of climatic or geophysical conditions (Webster et al., 2017). Another is to assess the genetic diversity of different populations, and how they contribute to the adaptive potential of the species as a whole. Trout Unlimited took this approach for a portfolio plan of the eastern range of Brook Trout (Salvelinus fontinalis; Fesenmyer et al., 2017). They assessed the genetic diversity of different population patches of Brook Trout and the habitat condition of those patches (Fesenmyer et al., 2017). This allowed them to prioritize stream restoration to maintain a portfolio of genetic diversity (Fesenmyer et al., 2017).
In the Northeast, portfolio planning has been useful for anadromous River Herring (Alosa spp.) populations. River Herring spawn in coastal pond systems that vary widely in size and environmental conditions across the Northeast U.S. Migration timing into these pond systems is highly variable and has shifted in some, but not all, monitored systems (Dalton et al., 2022; Ellis & Vokoun, 2009; Huntington et al., 2003; Lombardo et al., 2020). Adult migration timing has shown both advancements and delays likely due to the interaction of climate change and barriers to aquatic connectivity (e.g., dams and culverts) (Legett et al., 2023). High phenological variation can be beneficial if it corresponds to a species’ flexibility in response to different environmental conditions (i.e., phenotypic plasticity). However, high variability can create challenges for making reliable predictions. In this scenario, portfolio planning could be useful to identify multiple systems across River Herring’s spawning range that support diverse thermal habitat conditions and span the full breadth of their spawning phenological window. A coastwide conservation plan could also factor in temporal buffers that account for increasing phenological variation and the occurrence of extreme events (e.g., spring Nor'easters and other storms) to proactively protect the species from additional stressors that disrupt or delay migration (e.g., water withdrawals and coastal development projects) during this critical life history period.
References
Adapted from
Staudinger, M.D., A.V. Karmalkar, K. Terwilliger, K. Burgio, A. Lubeck, H. Higgins, T. Rice, T.L. Morelli, A. D'Amato. 2024. A regional synthesis of climate data to inform the 2025 State Wildlife Action Plans in the Northeast U.S. DOI Northeast Climate Adaptation Science Center Cooperator Report. 406 p. https://doi.org/10.21429/t352-9q86