Guess what. Animals respond more quickly to climate change than plants. Flora and fauna are changing their ranges as warming temperatures make their historic areas unsuitable. Where possible, they shift uphill to higher elevation (cooler), or further north if nothing obstructs northward movement, such as urban development. Animals shift faster than plants because plants primarily move using seeds. But to survive everyone needs to move in the same time span because animals and plants are interdependent. Animals need plants for food, protection from predation and weather, and often for nesting. Plants depend on animals for pollination, seed dispersal and other needs (e.g., soil aeration and fertilization). When animals leave an area, plant seeds have less chances to hitch rides to the new range. Ecosystems disintegrate.
Research in California showed that habitat shifts happen faster for weedy plants than for natives, although no differences were seen among life forms (tree, herb, shrub). This and a comparison with previous studies reporting more rapid changes by animals was discussed in Climate Change Is Leaving Native Plants Behind.
The results of the analysis warn that native plants are struggling to keep up with changes around them as pollution from fuel burning and deforestation continues to warm the planet. Earlier research into the movement of Californian animals shows they’re shifting more quickly than the native plants.
The big takeaway is that species are on the move, and they’re moving at different rates,” said Jon Christenson, a scientist and historian at the University of California, Los Angeles. “Which raises the concern that the ecosystems of California could be unraveling.”
Weeds are moving faster than native plants: one in eight native plants has shifted to higher elevations while one in four non-native plants (weeds) shifted. Seed size affects movement, with small seeded plants like grasses moving faster than larger seeded plants like manzanitas. It’s possible that new ranges will be dominated by weedy grasses. California’s native grasses are already seriously diminished due to past actions like habitat destruction, planting non-native grasses in pastures, and accidental introduction of weedy grass seeds.
Invasive weeds were the speediest plants to move and expand their population size, (27 percent have moved). This is a serious concern as they can crowd out the slower, less adaptable native plants (only 12 percent have moved) by taking over suitable habitat before the natives arrive. In general, animals are more dependent on native plants than on introduced, although some animals have shifted to non-natives, such as the overwintering monarchs who now use eucalyptus trees when the native Monterey pines were reduced by coastal development. But without some of the native plants available, animal populations will decrease. Without animals, plants will produce fewer seeds and have fewer opportunities to move seed to better habitat.
Researchers looked at a database of over 2 million plant specimens in digitized collections from 35 herbariums and found 681,609 specimens to study. These herbariums house over 100 years of plant collections and are specialized museums that store dried and pressed plants, including ferns, mosses, and algae. Each is labelled with useful information: date and where collected at a minimum. Many also include site characteristics such as location, slope, aspect (which direction the slope faces), vegetation type (e.g., forest, grassland, woodland, chaparral) and lists other plants in the same locale.
Herbarium collections tell us how plants are, and were, distributed across the landscape and how they occur together in communities (e.g., mixed conifer forest, oak woodland, annual grassland, and manzanita chaparral). By comparing specimens, we learn how these assemblages change over time.
Comparing this plant research to studies of animal movement in response to climate change shows that more animals are moving than plants, and at a faster rate. For example, one study on bird species in California’s Sierra Nevada mountains looked at 53 species resurveyed nearly a century apart in 82 sites at four different elevations. Of these 53 species, 48 (90.6 percent) moved along with their preferred niche. In a similar time span, only 12 percent of the native plants have made a similar shift. (Niche is a set of environmental conditions that restricts each species to a geographical range where it can prosper.)
One important niche characteristic is temperature and California’s temperatures rose by about 1°C (nearly 2°F) in the past century. Studies comparing present ranges of animals and plants to that of the past century do not necessarily predict what will happen in the next hundred years due to the increasing magnitude of climate change induced habitat changes. The only birds in the study who didn’t shift were those adapted to low elevation, human developed lands: Nuttall’s Woodpecker, California Thrasher, Anna’s Hummingbird, Black Phoebe, and Western Scrub-Jay.
A message from this research is that habitat types — the collection of flora, fauna, and environmental conditions like soil type, rainfall, humidity (fog) — are disintegrating in response to climate change pressures. What happens in California isn’t specific to that state — the huge area covered and the diversities of habitats and climates in California makes this research relevant elsewhere. Many organisms (and communities) will hit a dead-end and not be able to move any further due to being at the top of a mountain, reaching a freeway or water body. New assemblages of plants and animals can form, ultimately, over many centuries, but while this is happening, species are lost.
One action item from these studies is to determine where niches and habitats will be and add these areas to conservation programs. An example is coast redwood forests being evicted from the southern end of their range by climate change and needing to move north. Let’s help flora and fauna climate change refugees find new homes by protecting what they need.