Unbalanced species losses and gains lead to non‐linear trajectories as grasslands become forests

Abstract

Questions Rates of plant community shifts after environmental changes depend on how quickly affected species are gained and lost. Understanding how the balance between extinction and colonisation varies over time, and how it is influenced by local and landscape factors, is essential to understanding overall change trajectories. Investigating change requires data at several time steps over sufficient periods, and the paucity of such data represents an important knowledge gap. We ask: (a) how variation over time in the rates of species’ extinction and species’ colonization controls the trajectory of biodiversity change in abandoned semi‐natural grasslands? and (b) can landscape composition and habitat history modify change trajectories by acting independently on groups within plant communities? Location Sweden, Stockholm Archipelago. Methods We use data on plant composition, management history and landscape context in former grasslands, abandoned at different points since 1901, in a space‐for‐time analysis, comparing rates of grassland species loss and forest species establishment and investigating resulting biodiversity trajectories. Results Grassland species declined steeply in recently abandoned habitats before levelling off, while the accumulation of forest species was linear, with no plateau reached even at the longest time since abandonment. Hence, we observed a trough in biodiversity, with an initial decline in overall species richness followed by a partial recovery. Only forest species gain was enhanced by nearby habitat availability. Conclusions Information on community compositional changes over short time periods may be misleading about the extent and even direction of ongoing biodiversity gains and losses. Moreover, the non‐linear changes observed suggest thresholds in time, after which succession to the forest community accelerates and the ability to manage a return to the grassland community diminishes. Accounting for the combined influence of landscape composition and history is key to fully understanding community shifts over time.

Regional species gains outpace losses across North American continental shelf regions

“…Therefore, population trends related to extirpation and community composition change are likely to be transient and not well explained by classical equilibrium dynamics (Hastings, 2001; Hastings et al, 2018). Studies examining the dynamics of gains and losses within terrestrial ecosystems in periods of rapid warming reveal that these community–climate disequilibria have the potential to persist long past the period of warming (Butterfield et al, 2019; Kimberley et al, 2019; Menéndez et al, 2006).…”

Modelling coupled human–environment complexity for the future of the biosphere: strengths, gaps and promising directions

“…Along with existing plant-trait databases (e.g. [160,161]), other ecological datasets can be immediately applied to CHES models such as an invasive plant dataset with associated bioclimatic variables [162], a database of ecosystem services [163] as well as land use datasets that already contain human environment coupling that can further motivate future models [164][165][166].…”

Semi-natural habitats in boreal Europe: a rise of a social-ecological research agenda

“…For example, it has led the advanced understanding on how historical land use has affected the development of semi-natural habitats today (e.g., Pärtel et al 1999, Eriksson et al 2002, Olsson et al 2011, Ödman and Olsson 2014, Cousins et al 2015. The increasing knowledge on landscape history and the effect on present biodiversity in semi-natural habitats can assist developing approaches for alleviating negative side effects of rapid landscape and habitat changes in conservation (e.g., Eriksson et al 2002, Kimberley et al 2019). However, despite the prominence of research on semi-natural habitats in Sweden, it is too early to say to which degree these research results also drive the political agenda.…”