Fertilizer contains essential plant nutrients such as Nitrogen and Phosphorus within different mixes. But if nutrients are present at high levels, they are often not absorbed into the ground and instead end up in our waterways. Hence, when fertilizer is applied in excess, these nutrients can get washed into our watershed and lead to consequential and unfavorable ecological, health, and economic, outcomes.
Ecological Impacts of Fertilizer
Excess fertilizer can cause an increase of algae, a simple aquatic plant in the water, and lead to algae blooms. Increased algae can result in lowered dissolved oxygen in the water column, promoting decreased levels of dissolved oxygen. This can sometimes lead to "dead zones" -- areas in the waterbody that can no longer support life. Algae blooms are not only visually unappealing, but they can also clog waterways, lead to fish kills, and create a public health risk.
Improper fertilizer use can also negatively impact water quality. Fertilizers that enter the waterway can contribute to increased algae and aquatic plant growth, creating more turbid, or cloudy conditions in the water. Increased turbidity results in decreased water quality. This ultimately reduces light penetration and impacts habitat which relies on photosynthesis to survive like seagrasses and coral reefs.
Fertilizer can contribute to algae growth which can overrun natural habitats, and lead to habitat loss. Increased algae can smother habitats like seagrass beds, sometimes creating area-wide dieoffs. Loss of important habitats like seagrasses can impact natural aquatic species and wildlife. These dramatic changes in habitats, biodiversity, and species richness can result in a regime shift -- a large, abrupt change in an ecosystem. Scientists believe that Biscayne Bay, for example, is experiencing a regime shift from a seagrass dominated ecosystem to algae dominated ecosystem, due in part to nutrients running off from land into the water.
Google satellite images illustrating a massive seagrass dieoff off the Julia Tuttle Bridge in Miami Beach, FL. The darker regions represent seagrass coverage -- as time progresses from 2011-2016, the darker regions begin to shrink. (Source: Google Satellite; Miami Herald).
Health Impacts of Fertilizer
Improper fertilizer use can cause HAB health impacts on humans. Harmful Algae Blooms (HABs) occur when algae grow out of control. Some algae produce toxins that can be harmful to humans. These toxins may concentrate in seafood which, when consumed by humans, can lead to health problems. Also, some algae produce airborne toxins which can be harmful to humans when respired. Toxins may include gastrointestinal, cardiovascular, or neurological symptoms, and respiratory issues -- especially in asthmatics, children, and elders.
Additionally, algae blooms pose severe impacts on wildlife -- both the wildlife and their habitat. Blooms can cause fish kills, marine mammal and wildlife mortality, and other physical injuries to species. In addition, they can smother aquatic habitats, making it difficult for these species to survive.
Economic Impacts of Fertilizer
Algae blooms can contribute to destructive environmental events such as fish kills, negatively impacting commercial fisheries. These fish kills can lead to harvesting closures -- when the state limits the number and type of fish that can be kept. Because of this environmentally induced supply shift, the prices of fish can increase. This could ultimately result in significant economic loss to fishing-dependent communities.
More frequented algal blooms can impact tourism and recreation because they can create both public health and environmental hazards. Florida's economy relies heavily on tourism in coastal areas. Tourism contributes hundreds of millions of dollars to the economy, as well as provides thousands of jobs annually. Without tourist and water-based recreation, coastal economies could be significantly impacted.
HABs can also lead to increased medical costs. People exposed to toxins in the air or in seafood may become ill and incur additional expenses such as medical treatment, hospitalization, or loss of wages if struck with an ailment.
Storm resiliency is extremely important to the survival and sustainability of coastal communities. Algae blooms can impact our naturally storm-resistant ecosystems. Coral reefs and seagrass beds improve coastal resiliency. When algae blooms occur, these important ecosystems may be altered and can even lose functionality, resulting in a species dieoff. Without these ecosystems, coastal communities may experience increased storm surge and flooding, storm-related damage, and higher economic loss during events.
Miami Beach, FL (Source: Time Out Magazine)
The impacts of excess or improper fertilizer use are extensive. Algae blooms can be severely harmful to marine and human lives combined. Biscayne Bay is already starting to suffer from massive seagrass die-offs and algae blooms. It is critical that we make a conscious effort to reduce land-based pollution, using best management practices to reduce the use of residential fertilizer near and around our waterways.