Moving to Survive: Species Range Shifts Explained

If a map shows every location where a specific type of bird lives and reproduces, then that entire area represents the species' home. If we define that area of occupancy, then it is called the biological range.

If the climate in a specific region gets too hot for a cold-loving animal, then that animal must either move to a cooler area or face local extinction. If it moves to a new area, then its range has shifted.

If the regions near the equator become too warm, then the cooler temperatures needed for survival are found closer to the ends of the Earth's axis. If species follow these temperatures, then they move toward the poles.

If air temperature generally drops as you go higher above sea level, then the top of a mountain is cooler than the base. If an animal's current home becomes too hot, then moving up the slope allows it to reach a cooler climate.

If the environment changes in a way that makes survival difficult (like heat or lack of water), then the species will shift. While seasonal light changes affect migration, they do not cause a permanent range shift.

If seeds are carried by wind, water, or animals to new areas with better climates, then new plants will grow there while old ones die out in the heat. If the location of the population changes over generations, then the plant range has shifted.

If a forest animal needs to move north to find cooler woods but hits a large concrete urban area, then it cannot safely pass. If it cannot pass, then its ability to shift its range is blocked by human infrastructure.

If a flower moves its range north to stay cool but the bees that pollinate it stay behind, then the two species are no longer together. If they are separated, then the "match" required for the flower to reproduce is broken.

If an animal cannot swim across an ocean or survive the heat of a desert, then those features act as walls. If these walls exist, then the species is trapped even if the climate elsewhere is better.

If surface waters become too warm due to sunlight and climate change, then the colder water is found further down. If fish move to these lower levels to maintain their body temperature, then they are performing a vertical range shift.

If the environment changes more rapidly than a species can move or adapt, then the individuals will die off. If the entire population dies because it is trapped in a bad climate, then the species becomes extinct.

If an animal moves south for the winter and returns in the spring, then it is a temporary cycle (migration). If a species slowly moves its entire population to a new forest because the old one is too dry, then it is a permanent range shift.

If a population permanently changes where it lives to track a specific climate, then it is a range shift. Arriving earlier in the spring (D) is a change in timing (phenology), not necessarily a shift in the geographic range.

If a specialist animal only eats one type of plant, then it can only move if that plant moves first. If a generalist can eat anything, then it can move to any new area that has the right temperature, making it more flexible.

If we measure how many miles per year a certain temperature zone moves north, then we are calculating its velocity. If a species moves slower than this velocity, then it will be "left behind" in a climate it cannot survive.

If a shifting species enters a new territory, then it needs resources to survive. If the native species already uses those resources, then the two groups will compete, which can lead to one group declining.

If humans provide connected paths and varied habitats, then animals have a clear way to move. "Assisted migration" involves humans physically moving plants or animals to safer zones.

If the equator is the hottest part of the planet, then species trying to escape heat would move away from it. If they move away from the equator, then they are moving toward the poles (North or South).

If we look at when things happen in nature (blooming, nesting, migrating), then we are studying phenology. This often changes alongside the geographic range shifts of a species.

If every species moves at a different speed or in a different direction, then the relationships between predators, prey, and plants are broken. If these systems collapse, then the total variety of life (biodiversity) decreases.