Q&A – Are Florida’s Manatee Deaths The Result Of A Growing Population?
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Today’s entry: Brian, I’m wondering if you’ll address a manatee question I’ve been wondering about for a while. For months we’ve heard of the record manatee deaths and today you reported on the need for additional resources to help support the ongoing efforts to combat starvation. While sad, something occurred to me when I first heard of this problem. Could record deaths and starvation be a byproduct of a recovering population? I’ve only heard manatee deaths discussed as a negative, and while it’s certainly sad so many are starving, even without human intervention there’s a limit to how many manatees Florida’s waterways would be able to support. As I recall, the manatee population had been growing in recent years.
Bottom Line: Your points are valid as part of the big picture conversation regarding the record manatee deaths recorded in Florida this year. The Florida Fish and Wildlife Conservation Commission conducted annual surveys of the state’s manatee population from 1991 to 2019 each January. During that time, most of which included manatees being protected under the Endangered Species Act, the manatee population steadily improved. During the first FWC survey in 1991 only 1,267 manatees were identified statewide. By 2000 the population nearly doubled to 2,223. The population more than doubled over the next ten years as 2010’s survey revealed a record 5,077 manatees. The population continued to grow and as of the most recent survey estimates – there were an estimated 8,800 manatees.
FWC hasn’t conducted an official manatee survey over the past two years due a combination of environmental conditions and the pandemic. So, what happened with Florida’s manatee population between January of 2019 and the spring of 2021? We really don’t know but since the trend in population had consistently been higher and with the pandemic having slowed traffic/human intervention in the waterways considerably last year, it’s likely they at least maintained previously known population levels. That takes us back to your point. Could it be that the considerable growth in Florida’s manatee population over 30 years reached the tipping point this year? Could the record deaths resulting primarily from starvation be a natural byproduct of reaching a peak sustainable population? There’s logic that suggests population growth is at a minimum a contributing factor, though we do know that our impact is still the greater of the two factors. Here’s why.
Early this year NOAA declared an “unusual mortality event” and federal studies are now underway to determine how best to curb the sudden surge in manatee deaths. The top reason for manatee deaths is starvation as seagrass has continued to die off due to the years of toxic algae build up and regular discharges from Lake Okeechobee. This has specifically contributed to the studied loss of the 32,000+ acres, or 45%, of seagrass in estuaries on the Treasure Coast since 2010 - where the largest manatee population is supported in the state. It’s important to note that the “loss” is completely attributable to issues associated with our activity, mainly Lake O’ discharges as opposed to a larger manatee population feeding in the estuary. Feeding manatees act as an underwater lawn mower. They trim the grass but they don’t kill it. The term loss is used when biologists determine the root structure for seagrass no longer is present. That’s on us. Independent of boating and other related activities that contribute to seagrass destruction, our activities are responsible for wiping out nearly half of the most important habitat in the state in just a decade. Not surprisingly, most of the record setting deaths this year have been recorded in those estuaries.
To your broader point, the combination of a growing population contrasted with a rapidly declining habitat has reached a capitulation point this year. So yes, part of what’s happening here is a byproduct of the progress we’ve made in helping aid in the recovery of the manatee population over the past thirty years. In that regard we can take solace in the fact that even with a record number of manatees dying this year, now estimated to be between 11%-15% of the total population, the population has only fallen to about the levels previously seen in 2018 and that are about 7 times greater than when the state started tracking the population in 1991. Conversely, a 45% habitat loss of the most critical estuary in ten years is unsustainable if we’re to maintain a healthy manatee population. That’s why, despite the progress in the manatee population we’ve made until recently, we can’t just assume it’ll all work out without meaningful change on our part. Thankfully, that’s hopefully starting to happen with the Army Corp of Engineers recent adoption of a new discharge plan.