Rapid and ongoing change creates novelty in ecosystems everywhere, both when comparing contemporary systems to their historical baselines, and predicted future systems to the present. However, the level of novelty varies greatly among places. Here we propose a formal and quantifiable definition of abiotic and biotic novelty in ecosystems, map abiotic novelty globally, and discuss the implications of novelty for the science of ecology and for biodiversity conservation. We define novelty as the degree of dissimilarity of a system, measured in one or more dimensions relative to a reference baseline, usually defined as either the present or a time window in the past. In this conceptualization, novelty varies in degree, it is multidimensional, can be measured, and requires a temporal and spatial reference. This definition moves beyond prior categorical definitions of novel ecosystems, and does not include human agency, self-perpetuation, or irreversibility as criteria. Our global assessment of novelty was based on abiotic factors (temperature, precipitation, and nitrogen deposition) plus human population, and shows that there are already large areas with high novelty today relative to the early 20th century, and that there will even be more such areas by 2050. Interestingly, the places that are most novel are often not the places where absolute changes are largest; highlighting that novelty is inherently different from change. For the ecological sciences, highly novel ecosystems present new opportunities to test ecological theories, but also challenge the predictive ability of ecological models and their validation. For biodiversity conservation, increasing novelty presents some opportunities, but largely challenges. Conservation action is necessary along the entire continuum of novelty, by redoubling efforts to protect areas where novelty is low, identifying conservation opportunities where novelty is high, developing flexible yet strong regulations and policies, and establishing long-term experiments to test management approaches. Meeting the challenge of novelty will require advances in the science of ecology, and new and creative. conservation approaches.

No abstract

We measured summer microhabitat use, availability, and selection by age-0 Chinook salmon Oncorhynchus tshawytscha in the Big Creek drainage, Idaho. Age-0 fish selected for low-velocity (0-25 cm/ s), moderate-depth (40-80 cm) habitats that were located within 80 cm of cover. Pools (52%) and runs (38.5%) were the most commonly used habitat types, while pebbles (33.7%) and sand (23%) were the most often used substrates. Cover type use was predominated by woody debris (54.8%) and rock outcrops (23.7%). Run (38.5%) and riffle (32.9%) were the most available habitats in Big Creek, while pebble (38.4%) and cobble (28.2%) were the most available substrates. Mean water velocity (47 cm/s) availability and distance to cover (108 cm) availability were greater than those selected by age-0 Chinook salmon, while mean total water depth (30 cm) availability was lower than that selected by the fish. Linear regression was used to show that an increase in juvenile Chinook salmon total length was significantly (P , 0.05) related to increased total water depth (r 2 ¼ 0.68), focal water depth (r 2 ¼ 0.73), and focal water velocity (r 2 ¼ 0.49) use. The relationship of habitat use and fish total lengths indicate that even within a short temporal period, juvenile Chinook salmon will select for different habitats as they grow. Upper and lower Big Creek microhabitat availability characteristics differed significantly (P , 0.05). Upper Big Creek had more fish per unit of preferred rearing habitat than lower Big Creek, which suggests that either summer microhabitat availability or redd density partially explain the density differences observed in Big Creek. Microhabitat use and availability data were useful for identifying habitat selection of age-0 Chinook salmon in Big Creek. The data from this study can be used for future identification, quantification, and restoration of suitable Chinook salmon rearing habitat in other Pacific Northwest streams.

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large‐scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America. We sampled insects with Malaise traps during 2019–2021 (N = 1041 samples) and examined the biomass of insects in relation to temperature and time of season. Our samples mostly contained Diptera (33%), Lepidoptera (19%), Hymenoptera (18%), and Coleoptera (10%). We found strong regional differences in the phenology of insects and their response to temperature, even within the same taxonomic group, habitat type, and time of season. For example, the biomass of nematoceran flies increased across the season in the central part of the continent, but it only showed a small increase in the Northeast and a seasonal decline in the Southeast and West. At a smaller scale, insect biomass at different traps operating on the same days was correlated up to ~75 km apart. Large‐scale geographic and phenological variation in insect biomass and abundance has not been studied well, and it is a major source of controversy in previous analyses of insect declines that have aggregated studies from different locations and time periods. Our study illustrates that large‐scale predictions about changes in insect populations, and their causes, will need to incorporate regional and taxonomic differences in the response to temperature.