Differing climatic mechanisms control transient and accumulated vegetation novelty in Europe and eastern North America

Abstract

Understanding the mechanisms of climate that produce novel ecosystems is of joint interest to conservation biologists and palaeoecologists. Here, we define and differentiate transient from accumulated novelty and evaluate four climatic mechanisms proposed to cause species to reshuffle into novel assemblages: high climatic novelty, high spatial rates of change (displacement), high variance among displacement rates for individual climate variables, and divergence among displacement vector bearings. We use climate simulations to quantify climate novelty, displacement and divergence across Europe and eastern North America from the last glacial maximum to the present, and fossil pollen records to quantify vegetation novelty. Transient climate novelty is consistently the strongest predictor of transient vegetation novelty, while displacement rates (mean and variance) are equally important in Europe. However, transient vegetation novelty is lower in Europe and its relationship to climatic predictors is the opposite of expectation. For both continents, accumulated novelty is greater than transient novelty, and climate novelty is the strongest predictor of accumulated ecological novelty. These results suggest that controls on novel ecosystems vary with timescale and among continents, and that the twenty-first century emergence of novelty will be driven by both rapid rates of climate change and the emergence of novel climate states. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

Protected-area targets could be undermined by climate change-driven shifts in ecoregions and biomes

“…We project changes to the distribution and extent of biomes and the terrestrial ecoregions they encompass, including the emergence of regionally novel climate conditions that may drive the development of novel ecosystems 41 . We then assess the proportion of each ecoregion that is projected to: (1) remain climatically stable with conditions similar to the current ecoregion (and by default, biome), (2) transition to conditions representative of other ecoregions or biomes, and (3) remain stable and intact (low human modification), as these may represent strategic opportunities for expanding the PA estate.…”

The rise of novelty in marine ecosystems: The Baltic Sea case

“…The baseline also depends on the context of the study, the time scale and the characteristics of throughout the past (e.g. 15,000 years in Burke et al, 2019;and in Finsinger et al, 2017; more than 100 years in Radeloff et al, 2015; and in Williams et al, 2019). The analysis of such long-term datasets increases the likelihood of identifying truly novel conditions (i.e.…”

Changes in limiting factors for forager population dynamics in Europe across the Last Glacial-Interglacial Transition

“…The paleoclimatic simulation data used here was originally generated to evaluate changes in European and North American fossil pollen data and vegetation novelty since the Last Glacial Maximum 27 . Source climate surfaces were aggregated to centennial means from the original decadal averages of monthly values.…”

“…We couple this to a suite of quantile Generalised Additive Models (qGAMs) to describe changes in maximum (90-percentile) population density as a univariate function of environmental variables related to the effect of temperature and precipitation on available energy, annual variability, and productivity. We then use the downscaled centennial average-conditions of each predictor derived from a transient climatic simulation (CCSM3 SynTrace-21 27 ) and the best performing univariate qGAM models to hindcast hunter-gatherer population densities between 20ky to 8kyBP. We define the limiting environmental factor as the variable predicting the lowest population density at a given place and time.…”