Ray Christman: Mike, we have now experienced five hurricane or Tropical Storm events in 24 months, including three this year of which two occurred back-to-back in recent weeks. While some, like Ian in 2022, were more severe, each had a meaningful impact on Naples, southwest Florida and other parts of our state.
What does your research and study lead you to believe are the primary causes of these intensifying and seemingly more frequent weather events? What do you believe is happening and why?
Mike Savarese: The nature of tropical storms and hurricanes is changing. Storms are rapidly fueling, increasing in intensity very quickly; they are larger, wetter, and traveling more slowly. All these characteristics are consistent with the expectations associated with climate change. And all these changes make storms more dangerous, generating higher wind velocities, increasing the depth and extent of storm surge, and inundating landscapes with more precipitation. These are all characteristics we have seen associated with hurricanes impacting the Southwest Florida coast in recent years: Irma (2017), Ian (2022), Idalia (2023), and Debby, Helene, and Milton (2024). Sea surface temperatures are significantly warmer than in the recent past, and atmospheric and ocean warming are scientifically established effects of human-induced changes to our atmospheric – a consequence of an increase in greenhouse gases.
There is a relatively new field of climatological research known as “attributional science” that uses computer modeling techniques to determine if a greater frequency or intensity of some climate effect is caused by climate change or merely random processes. Perhaps the greater frequency and intensity of wildfires or of major hurricanes we are experiencing is due to just natural and random variability? But through attributional science great strides have been made in recent years establishing cause and effect: there is growing evidence that climate change is responsible for many of the exacerbated climate impacts we’ve endured.
RC: What trends can you share about warming ocean temperatures and rising sea levels in the Gulf proximate to Naples, Collier County and southwest Florida? What does the data suggest has been happening over the past 30-50 years?
MS: Rising sea level is another climate change effect that is exacerbating the impacts of hurricanes. Storm surge and wave height sit on top of sea level. As sea level increases over time, the depth and extent of storm surge inundation increases. As a consequence, we become more vulnerable to storm surge as we move into the future.
Based on the National Oceanic and Atmospheric Administration’s (NOAA) empirical measurements (2022), sea level has risen in our portion of the Gulf of Mexico at a rate of 4 mm / year between 1993 and 2006. This has accelerated to a rate of 8 mm / year between 2007 and 2023. Combined, this accounts for 192 mm of Sea Level Rise (SLR) since 1993, which is equivalent to approximately 7.6 inches. Storm surge produced by Hurricane Milton in 2024 sat slightly over half a foot higher than it would have had it made landfall in 1993.
RC: That’s a significant increase!
MS: Yes, it is. NOAA also provides a collection of sea-level rise projections (their low, intermediate-low, intermediate, intermediate high, and high SLR curves), which make assumptions for regional variations and different greenhouse gas management strategies the planet might adopt. These project forward to 2050.
When you compare the actual rise rate measured here in Southwest Florida against the NOAA curves, our region is currently traveling somewhere between the Intermediate-High and High curves, which predicts a SLR somewhere between 0.45 – 0.51 meters by 2050 relative to 2000. This equates to a rise of 1.48 – 1.67 feet by 2050, triple the rate of the past 30 years. A sea-level rise of this magnitude not only creates greater vulnerability to storm surge, but it will generate frequent nuisance tidal flooding events of our coastal landscape.
Each coastal region has its own particular characteristics that generate variations in the magnitude of SLR. Some coastal regions are naturally subsiding; others are slowly uplifted; and oceanographic currents can pile more water onto certain coastal stretches. SWFL’s projected SLR magnitude, for 2050, is higher than the global average (0.45 m > 0.24 m) and higher than that for the contiguous U.S. (0.45 m > 0.38 m).
Many of our recent impactful hurricanes originated in the Gulf of Mexico or significantly intensified while traveling over the Gulf. The Gulf of Mexico, like all marine bodies of water, has warmed appreciably over recent decades in concert with the warming of the atmosphere. I would argue the Gulf is particularly problematic. It is a relatively small body of water with a broad shallow continental shelf on its perimeter. This allows it to warm rapidly. The heat content of the Gulf in 2023 and 2024 was significantly higher than the running average between 2013 and 2023 (Brian McNoldy/ University of Miami) and may explain, in part, why rapid intensification was so pronounced these last two hurricane seasons. With respect to sea surface temperature, the Gulf of Mexico has warmed by 1.0°C (1.8°F) between 1970 and 2020, which equates to a warming rate of 0.34°F per decade. Notably, this is twice the warming rate observed in the global ocean (NOAA NCEI).
Collectively, the acceleration of sea-level rise and the warming of the Gulf predispose Southwest Florida to a future of more intense storms capable of generating appreciably higher storm surges.
RC: You have been deeply involved with the ACUNE model (Adaptation of Coastal Urban and Natural Ecosystems), which was developed to provide information about likely flooding patterns in Collier County given different assumptions. This tool is helping public officials in Naples and elsewhere better prepare and plan for future flooding events. Given this recent spate of storm events, how much alignment has there been with ACUNE model and its predictive abilities with what has actually happened on the ground?
MS: Modelers from University of Florida and U.S. Geological Survey developed ACUNE. I have served as a liaison for Southwest Florida, helping decision makers employ the tool. ACUNE’s predicted results for Hurricanes Helene and Milton have yet to be compared against the surge actually experienced; those storms are just a few weeks old. I do know, however, that ACUNE’s results aligned very well with the surge experienced during Hurricanes Irma and Ian. ACUNE is a phenomenal tool that can assist communities and decision makers adaptively plan for their future vulnerabilities to storm surge. As you mentioned, the City of Naples has the tool at its disposal, and ACUNE has helped the City in the creation and adoption of its climate adaptation plan.
RC: Let’s turn to the condition of our beaches and the impact of the recent storms on our beaches. After Ian, funding was committed by FEMA to build an emergency berm along our beaches to be followed by planting vegetation in the berm to provide stability and durability. The berm has now been largely destroyed by recent storms and the planting never occurred. Given this, what are your thoughts on the condition of our beaches and what steps might be taken to renourish and protect them going forward?
MS: The disconnect between the rebuilding of the beach through measures like berm construction and the planting of dune vegetation to stabilize the beach is troubling. FEMA-funded emergency berms were constructed in many locations along the Collier and Lee County coast, and all were effectively destroyed by the subsequent storms in 2023 and 2024. The expectation is that an emergency berm should be sustainable for 5 years, and our current storm climate obliterated the berms within two. There needs to be concerted planning. Dune vegetation must be cultivated in advance and each jurisdiction should be ‘at the ready’ to purchase and plant the vegetation as needed. This should be part of recurring maintenance. Berm construction without vegetation is wasteful.
Additionally, new strategies for dune fortification are a must. Regions of our coast with healthy dune systems, like the Bowman’s Beach portion on western Sanibel, performed much better than elsewhere through these 3 years of storms. Sanibel, unlike most of our other beach communities, has an advantage, however. Sanibel’s City government has maintained a large setback for development behind the beach: there is accommodation space for dunes. That space is lacking for most of Naples and Fort Myers Beach. There are, however, many creative designs for dune construction that blend hardened and natural infrastructure when space constraints exist. For example, hybrid dune designs exist that are “natural” and vegetated but cored by a hardened feature. The dune behaves like a dune during normal and mild storm conditions, but, if dune failure occurs during an extreme event, the hardened feature remains and functions like a sea wall.
RC: My sense is that many Naples residents – and residents up and down the Florida Gulf Coast – are unnerved by this spate of storms, particularly when combined with rapidly escalating property insurance costs and condo assessments. The question is whether and how we can adapt and better protect ourselves in the future. I know you are familiar with the City’s Climate Adaptation Plan, which City Council adopted in May of this year. What are your thoughts on priorities within that plan (or in addition to that plan) that Naples should focus on?
MS: Naples’ Climate Adaptation Plan compiles numerous strategies (47 in all with 31 prioritized as Tier 1 and 16 as Tier 2). The plan is wonderful and foresightful, and too comprehensive to detail here. Consequently, I thought I’d focus on just a handful, those that in my opinion directly relate the effects of sea-level rise and storminess and have broad implications for the general population of the city.
The plan calls for the “development of a Watershed Master Plan” to more comprehensively understand the City’s flooding risk, and this is identified as a high priority need. I believe this is a wise early step. Naples now has access to a more refined version of ACUNE, which has been redesigned to look at future storm inundation due to combined freshwater and sea water flooding. Additionally, many valuable lessons were learned from the aftermath of the storms since Ian; many vulnerabilities were revealed by the damage that was done. These lessons and tools provide data from which watershed planning can occur. Merely having such a plan can help reduce insurance costs for our residents through the National Flood Insurance Program rating system.
For me, and admittedly I am biased because of my background, a second highest priority concerns the “continuation of beach nourishment and expansion of dune revegetation”. I would couple this strategy with an “assessment of seawall use and implementation”. The dunes are the City’s “fortress walls”. When those walls are damaged due to breaching, overtopping, or complete obliteration, the protected assets behind – city assets, our people, culture, and economy – become significantly more vulnerable to the attack of storms and sea-level rise.
Ian’s near obliteration of dunes along the Collier and Lee County coastlines predisposed the region to more excessive damage by the subsequent storms of the last two years. And dunes restored without a concerted effort to vegetate them are short-lived structures. Seawalls are often viewed as undesired hardened shoreline features. Seawalls, however, are often the only available protective measure, particularly in areas where development is directly against the coast. A more sustainable dune, revegetation, and seawall strategy is needed. Merely replacing what was taken away is not sufficient.
The provision of “climate hazard protection for socially vulnerable neighborhoods” is also a most worthy priority. Many of Naples’s historically disadvantaged neighborhoods sit on landscapes that are highly vulnerable to storm flooding. Those neighborhoods residing on the eastern side of the city adjacent to the west flank of the Gordon River and those neighborhoods along Naples Bay’s and the Gordon River’s tidal tributary creeks (e.g., Haldeman Creek, Rock Creek) are all at greater risk and house lower income residents and families.
Also included is a recommendation for “incorporating sea-level rise considerations into City planning and design”. SLR will continue to exacerbate the impacts of storms and, as noted above, will begin to impose its own effects through nuisance flooding. Adaptive measures requiring reinvestment now should be designed for sustainability under future conditions and not those of the present.
RC: This discussion of resilience and adaptation strategies also brings us back to the US Army Corps of Engineers Coastal Storm Risk Management study, which is now in its second iteration and nearing completion. The first iteration, completed in 2020, emphasized physical infrastructure investments like sea gates, floodgates, and seawalls. At the time, many in the community criticized that approach as overly intrusive and impactful to our coastline.
The second iteration seems to be emphasizing “natural infrastructure” like dune building and mangrove plantings. What mix of investments and priorities do you think makes most sense to protect Naples from future storms? Is some sort of “hybrid” approach drawing on the best ideas for both natural and physical infrastructure investments the best approach?
MS: The Army Corps’ planning process has vacillated between “too hard” and “too soft”. The original plan, admittedly, was engineering heavy, with lots of hardened features, the types of infrastructure that would likely change the aesthetics and culture of coastal Collier County. The present plan eliminates all of those hard structural features and emphasizes the creation of a more formidable dune (one that is higher and girthier). Maybe the more sustainable, Goldilocks solution is somewhere in between.
Surge is a sneaky adversary. It can inundate coastal communities from the Gulf-side, but also from behind by seawater incurring from the back barrier bays and rivers. Naples, for example, is vulnerable from that backside inundation by water flowing from Naples Bay back to the Gulf. The back flow can be extreme enough to erode surge channels through the dune field and beach, something that was experienced during Hurricane Ian in Ft Myers Beach, Sanibel, and Lovers Key. This erosion caused much of the destruction to homes and businesses in these communities. Such vulnerabilities can be anticipated and managed proactively before they occur.
One way to attenuate the returning surge is to have a broad mangrove fringing forest on the backside of a barrier island or on the landward bay shore. Naples has such habitat lining the east side of Naples Bay, which is a good thing. Similar mangrove-forested acreage sits along the lower reaches of the Gordon River, though this habitat is rather “skinny”, reducing its attenuation capacity. This mangrove habitat should be conserved and promoted. The backside of the Naples spit – the portion of Naples that sits between the Gulf and Naples Bay – lacks that capability. The landscape is developed right up to the western margins of Naples Bay. Other communities with similar constraints, like those in Miami-Dade County, have managed this interior surge vulnerability using sea walls.
RC: I’ve made a point – as I know you have – to better understand what other areas of Florida, especially on the east coast, have done and are doing to plan and prepare for climate change and intensifying weather events. The east coast cities and counties have been grappling with these issues longer than we have and my sense is that there is more city-county and regional collaboration there than currently exists in southwest Florida. What are your observations in this regard and what can we learn from these experiences elsewhere?
MS: The South Florida region (the counties of Monroe, Miami-Dade, Broward, and Palm Beach, plus the countless municipalities therein) has been addressing adaptation to and the mitigation of climate change effects for some time. They’ve had a 15-year head start relative to Southwest Florida. Our region could learn much from their experiences. The Tampa Bay region has also been proactive with respect to planning for sea-level rise and storm inundation. Ironically, that region has avoided major impacts from hurricane storm surge, though the storms impacting the west coast of Florida over the last 4 years could have easily imposed the same impacts there as experienced elsewhere on the Gulf Coast.
RC: Finally, let me ask you about the relationship between increasing coastal storm risk and water quality. There are reports the wake of recent storms of growing red tide blooms north of Naples from Tampa Bay to Lee County, perhaps heading to Collier County. And there are troubling indications of freshwater bacteria levels well above federal standards. What are your thoughts and observations on these interrelationships, not just now but in general for the future?
MS: One synergistic consequence of excessive runoff, either due to the extreme precipitation or surge associated with storms, is movement of hazardous materials through our waterways and into the Gulf. We often experience the input of nutrients and fecal bacteria entering those waterways after storms, and these can result in harmful algal blooms or pathogen-borne illnesses. This is somewhat afield from my expertise, but my intuition tells me the best practices to contend with these risks are well-conceived emergency management practices, which I believe are currently in place. Our potable and recreational waters are monitored well, and warnings are issued: beaches are closed; water boil advisories are issued. No doubt these problems will exist after every extreme storm or runoff event. Jurisdictions will need to invest more in monitoring and predicting these risks.
One other aspect of the relationship between more frequent and intense storms and water quality is the increased discharge of nutrients into freshwater bodies that flow into the Gulf. This infusion is caused by leaking septic tanks, aging wastewater facilities, agricultural operations, and other sources. Research has shown that it can and does contribute to harmful algal bloom outbreaks and red tide.
RC: Thank you, Mike, for your time and candid and informed thoughts on these important issues.
MS: You are welcome. Naples and all of southwest Florida have plenty of climate-related challenges we all need to work on in the coming years to build resilience into our systems.