Question

The Goldman Fund has hired you to summarize the effects of climate change on plant and animal species found in California. In your summary, please highlight what changes you might expect to see under global warming for different types of species and communities in California.   You are not expected to speak to specific species, instead think of broad categories (e.g nectar feeders or primary producers). Be sure to identify what ecological principles lead you to each of your hypotheses and what experimental evidence suggests the principle is true.

Answer 1

Biologists are becoming more and more concerned that global climate change will drastically reduce biodiversity. Some biologists estimate that 35% of animals and plants could become extinct in the wild by 2050 due to global climate change. If we can sufficiently reduce greenhouse gas emissions, many of them will still have a chance to survive and recover. In order to maintain a climate similar to that under which human civilization developed and similar to that which so many organisms are adapted, we need to quickly reduce the carbon dioxide in our atmosphere to 350 parts per million (ppm). Before the industrial revolution, atmospheric carbon dioxide levels rarely rose above 280 ppm; during the 2014 calendar year, carbon dioxide levels fluctuated between 395 and 402 ppm.

The climate change is putting species' very existence at risk and mechanisms are being triggered to make food webs collapse or habitats become less livable for particular animals or plants.

In January 2020, two widely reported studies highlighted the dramatic impact of climate disruption on wildlife and fisheries along the California coast. The first study showed that from 2014 to 2016, over a million common murres from Alaska through California — about 15% of the population — died as result of a marine heat wave known as the "Warm Blob." The Warm Blob wreaked havoc on California's normally cold, highly productive waters, causing fish like anchovies, sardine, sand lance, squids, and krill to move to deeper, colder waters and be less available in other ways. In turn, the marine life — from the blue whale to salmon to pelagic birds like the common murre — that feed on them suffered, competing with each other for what little food was left to be found. The result was a massive die-off of common murres. The second study shows that ocean acidification caused by carbon emissions is harming shell-building animals in the ocean, including Dungeness crab. The study found that larval Dungeness crabs' shells suffer damage in west coast seawater, putting at risk the most lucrative fishery in California and a beloved local seafood. These newly documented impacts provide more evidence that we are running out of time to take action by drastically reducing our use of fossil fuels in order to slow the rate of climate disruption and to give birds and other animals more time to adapt.

Many rare, threatened, and endangered native plants are more susceptible to extinction caused by climate change due principally to small population sizes and limited suitable habitat types. While some animals have the ability to move when conditions become unfavorable, plants are immobile and thus can not as easily adapt to a quickly changing environment. Climate change may alter plant life stages such as leaf emergence or flowering period which may hinder survival and reproduction. Some studies estimate that endemic plant species’ ranges may shift up to 90 miles under intense climate change, but this shift may be a slow process relative to a rapidly changing climate. Furthermore, plants that are restricted to extremely specific habitats are especially at risk because while the climatic environment may shift, the soil and nutrient environment will not. Invasive plant species also pose a threat to native plants because invasives tend to do well in the changing conditions that climate change is thought to promote, and those invasives may then out-compete rare plants for vital resources. It is crucial that conservation efforts aim to conserve and manage large areas of protected habitat for plants, which may rely on dispersal and a variety of habitat gradients and varied microsites to cope with the changing environment.

Floral nectar is a vital resource for pollinators, thus having a very important role in ecosystem functioning. Ongoing climate warming could have a negative effect on nectar secretion, particularly in the Mediterranean, where a strong temperature rise is expected. In turn, decreased nectar secretion, together with shifts in flowering phenology can disrupt plant–pollinator interactions and consequently affect the entire ecosystem. For example, under fully controlled conditions, we tested how temperature influenced nectar secretion (through nectar volume, sugar concentration, sugar content, and number of flowers produced) in different plant species flowering from winter to summer. We compared the changes in nectar secretion under temperatures expected by the end of the century and estimated the effect of climate warming on nectar secretion of plants flowering in different seasons. We found a significant effect of temperature on nectar secretion, with a negative effect of very high temperatures in all species. Increasing temperatures, however, will affect differently the early-flowering (blooming in winter and early spring) and late-flowering species (blooming in late spring and early summer). Temperature rise expected by the end of the century will shift the average temperature beyond the optimal range for flower production and the sugar produced per plant in late-flowering species. Therefore, we expect a future decrease in nectar secretion of late-flowering species, which could reduce the amount of nectar resources available for their pollinators. Early-flowering plants will be less affected (optimal temperatures were not significantly different from the future projected temperatures), and may in some cases even benefit from rising temperatures. Consequently, climate warming will likely have a distinctive effect on both plant and pollinator populations and their interactions across different seasons.