As plants respond to climate change, they face the question: take the heat, or get out of the kitchen? Increased temperatures can affect mortality, photosynthesis, and regeneration. In turn, those effects have repercussions on carbon sequestration, habitat fragmentation, and wildfire risk. Understanding how plants have been impacted by past climates can inform us about the likely impacts of current and future climate change.
Wang, Y., Pineda-Munoz, S. and McGuire, J.L. 2023. Plants maintain climate fidelity in the face of dynamic climate change. Proceedings of the National Academy of Sciences 120(7): e2201946119.
A recent study explores how plants have responded during periods of change earlier in Earth’s history, and outlines two main strategies. “Climate fidelity” describes plants maintaining their climate niche by shifting their geographic ranges. The other option is niche flexibility, where plants with low climate fidelity shift into a new climate niche, adapting to changing conditions in their home range.
Neither strategy is without challenges. Range shifts are impeded by poor connectivity, and some species simply can’t disperse fast enough. Weathering changing conditions isn’t easy either. Though some environmental response traits can be more flexible, others have evolved over long periods of time for particular conditions. And whether range or niche shifts, plants need to maintain interspecies relationships with other organisms. All these factors complicate future predictions.
The study looked towards the future by way of the past: 18,000 years of history. Researchers examined North American fossil records for identifiable pollen, which can provide information about plant distribution and climate from the distant past. Researchers identified 16 plant taxa – a mix of deciduous trees, coniferous trees, and herbs – that comprised over 80% of the fossil pollen during this period.
Most taxa consistently exhibited climate fidelity, with three-quarters of the taxa exhibiting climate fidelity across all transition periods. Plants were generally able to track their climate niche even across continents, though there was less fidelity during extreme and rapid transitions. Only four taxa – elm, beech, ash, and birch – did not demonstrate consistently high climate fidelity. Elm, beech, and ash instead shifted their niches, while the range of birch contracted to smaller climate refugia.
During times of especially rapid climate change, plants which migrated longer distances were better able to maintain close climate niches. The study also identified “hotspots” where many taxa persisted through transitions, partially due to microclimates and limited human impact. However, these hotspots are largely in poorly connected landscapes today, which poses a challenge for continued range shifting on a large scale.
This research emphasizes how climate history has shaped the biogeography of plants in North America. This helps researchers predict which plants are most at risk from climate change, and which (including invasive species) might become problematic. As climate change accelerates, these results support well-connected landscapes that allow plants to move in order to maintain their climate niches. However, this can be a controversial issue, particularly when it comes to more intensive management such as assisted migration. Identifying resilient hotspots and maintaining connectivity to them may prove useful when designing corridors and prioritizing protected areas.
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