Q. How is the increase in water temperature affecting manatees? And seagrass meadows? -- Karin Holloway, London, England.
A. Some individuals have tried to simplify the effects of climate change on manatees by assuming that warmer waters will benefit the species. However, climate change is comprised of many more facets than just increasing water temperatures. We also cannot forget that manatees are part of an inter-connected aquatic ecosystem and are affected by the health of the plants and animals that share this and the surrounding terrestrial ecosystems. As humans adapt to climate change, other species, including manatees, are likely to be adversely affected.
Manatees, as herbivores, rely on seagrass as a primary food source. Seagrass grows in shallow, relatively clear waters. As sea level rises and is accompanied by increased turbidity and other impacts to water quality, seagrasses will likely be negatively impacted. Over time, seagrass beds may become reestablished, but major shifts in seagrass distribution and abundance could threaten Florida’s manatees, along with the many species of fish and invertebrates that also inhabit seagrass beds. With sea level rise, coastal habitats will also be threatened by armoring, as coastal towns and cities build seawalls to deflect rising waters. Such human-made structures can be detrimental to benthic habitats, including seagrass beds.
As coastal habitats change, manatees and boats may find themselves traversing new travel corridors that are not protected by manatee speed zones. Additionally, with a changing climate, manatees may extend their range farther north along the Atlantic coast and west along the Gulf coast. These adjacent states currently lack well-defined manatee speed zones, and residents are not accustomed to sharing the waterways with manatees. Manatees will face increased risk if they inhabit waters that lack safeguards for their protection.
The frequency of intense storms such as hurricanes will increase with climate change. Manatees may be killed, displaced, or suffer delayed effects to health and reproduction due to ecosystem changes resulting from intense storms (Langtimm & Beck 2003). The magnitude of impact varies with the destructiveness of the storm, the density of manatees in the area, the number of storms within a season, or coincidence with other mortality factors. Storm surge, in addition to rising sea levels, may cause saltwater intrusion in certain freshwater aquifers and other coastal waters that currently provide sources of freshwater vegetation and drinking for manatees. Manatees will need to adapt to such changes in order to survive. More intense rainfall and inundation events may result in more frequent red tide events, fueled by nutrient runoff to coastal waters. Such events can be fatal to large numbers of manatees.
Perhaps the most challenging obstacle that manatees will face with a changing climate is a lack of financial resources dedicated to the protection of this species. As human priorities shift to disaster reduction, concern for wildlife may decrease, and agency funding may shift away from individual species.