New Research Shows a Decline in Plant Diversity Could Affect Entire Ecosystems
Gardeners and nature lovers have noticed that plants are flowering earlier every year—a phenomenon generally attributed to climate change. New findings by Columbia researchers, however, are among the first to show that a decline in biodiversity may also play a role, magnifying the impact of climate change not just when plants flower, but on entire ecosystems.
“Biodiversity is an important component of all ecosystems,” said Amelia Wolf, a research scientist in Columbia’s Ecology, Evolution and Environmental Biology (E3B) department. “Plant and animal species are dependent on each other, and changes in biodiversity could have important consequences for the sustainability and functioning of ecosystems worldwide.”
Plants, for instance, flower for the sole purpose of reproducing—creating seeds to grow the next generation—and many plants rely on pollinators such as insects or birds to help with that process, Wolf explained. “If a plant flowers before its pollinators are active, the plant species can’t reproduce or may produce fewer seeds,” she said. Insects, birds, humans or other animals that depend on those plant species for food and habitat could then also be affected, Wolf added.
The timing of plant flowering is known to be influenced by nonliving aspects of an ecosystem, such as rising temperatures, and is widely regarded as a “fingerprint” of climate change. A warmer atmosphere affects soil temperature and water content. These variables, along with other parts of an ecosystem, trigger plants to mature and produce flowers—a critical stage in their reproductive cycle.
While numerous studies have found that such nonliving aspects influence the timing of biological events in plants, Wolf’s study is among the first to investigate the impact of plant-to-plant interactions. Wolf and her two co-researchers, from the University of California, Santa Cruz and the United States Geological Survey Western Geographic Science Center, set out to see if a decline in biodiversity had any effect on phenology, or the study of how the biological world times natural events. They wanted to see if the loss of plant species would affect the timing of events such as flowering for neighboring species of plants.
In 2007, the team set up an experimental field containing 16 different plant species in a California grassland. They created plots with varying numbers of species to see what effect diversity loss would have on the remaining plants, an experiment intended to mimic human impact on plant communities worldwide. Habitat destruction, invasive species, pollution, human overpopulation, over-harvesting, wildlife trade and general human consumption are major contributors to the enormous biodiversity loss that has earth scientists and experts gravely concerned, Wolf noted.
As the researchers reduced plant diversity, they observed warmer ground temperatures and changes in the soil and flowering timing similar in magnitude to the impact of global warming alone. For each species that was removed, the remaining plants flowered, on average, about a half day earlier than they would in plots with the greatest diversity. The removal of two species resulted, on average, in plants flowering a full day earlier than they would otherwise, and so on.
“This is not just about when tulips will reach full bloom,” Wolf said. “Biodiversity loss and the impact it has on plant phenology can impact an entire ecosystem. Plants and the communities in which they grow are interconnected and critically dependent on each other.”