FRAMING OF MANAGEMENT OF ECOSYSTEM SERVICES

Editors

Affiliations

Dr. Paul Sandifer began the discussion by pointing out that our ocean, coasts, and the Great Lakes affect us all in a variety of ways. They support tens of millions of jobs and contribute trillions of dollars to the national economy each year (IOPTF, 2010; Kildow et al., 2009). They host a growing number of important activities, including recreation, science, commerce, transportation, energy development, and national security. They provide a wealth of natural resources and ecological benefits and services. These benefits and services also help to protect coastal communities from damaging floods and storms. Coastal wetlands, for example, shelter recreational and commercial fish species and serve as a natural filter to help keep waters clean. He emphasized that while a large part of the economy, health, and national security depends on oceans, coasts, and the Great Lakes, these water bodies face a wide range of threats and pressures. Overfishing, pollution, coastal development, and the impacts of climate change, for example, are placing more stress on wildlife and natural resources, as well as on people and coastal communities.

The importance of the oceans, coasts, and the Great Lakes and the need to safeguard them and their benefits and services is the focus of a number of federal policies. The July 2010 Executive Order 13547, Stewardship of the Ocean, Our Coasts, and the Great Lakes¹ and the final recommendations of the Interagency Ocean Policy Task Force (IOPTF) (2010), which together constitute the National Ocean Policy was a landmark step toward addressing the challenges that face the health of our ocean and coasts, and the Great Lakes and the economies they support. The National Ocean Policy is the culmination of decades of work that builds upon prior bipartisan efforts to address the many challenges facing the ocean, Sandifer said. These efforts recognized that there is a need to have better and more efficient ways to manage and tend to our ocean, coasts, and Great Lakes resources.

To improve federal coordination and leadership, the National Ocean Policy establishes a National Ocean Council comprising heads of executive departments and federal agencies. The council is charged to provide sustained high-level engagement to oversee implementation of the National Ocean Policy. It also has as a goal to improve working relationships among federal agencies across the spectrum (resource management, economic development, national security) as embodied by the panel. In addition, the National Ocean Policy emphasizes the importance of ongoing coordination at the federal, state, tribal, and local levels through a Governance Coordinating Committee and with stakeholders through the Ocean Research Advisory Panel.

The National Ocean Policy is focused around nine priority objectives that provide a bridge between the National Ocean Policy and action on the ground and in the water. The National Ocean Policy's nine priority objectives help focus limited federal resources on meeting the essential needs of Americans and ensuring demonstrable outcomes and results. Four of the nine priority objectives address overarching ways the U.S. government must operate differently to better improve stewardship. The second category of objectives is considered areas of special emphasis. The priority areas are listed in Table 8-1.

TABLE 8-1

National Ocean Policy: Nine Priority Areas.

Sandifer pointed out that the priority area of coastal and marine spatial planning (CMSP) includes consideration of ocean and coastal ecosystem services. The IOPTF's Final Recommendations (2010) noted that CMSP is simply a planning framework to improve management of the myriad and often competing uses of ocean, coastal, and Great Lakes waters and resources. CMSP is to be science based, transparent, and informed by stakeholders and the public and to result in substantial economic, ecological, and social benefits. The Final Recommendations state that

CMSP is intended to improve ecosystem health and services by planning human uses in concert with the conservation of important ecological areas, such as areas of high productivity and biological diversity; areas and key species that are critical to ecosystem function and resiliency; areas of spawning, breeding, and feeding; areas of rare or functionally vulnerable marine resources; and migratory corridors. Enhanced ecosystem services and benefits can be attained through CMSP because they are centrally incorporated into the CMS Plan as desired outcomes of the process and not just evaluated in the context of the individual Federal or State agency action. CMSP allows for a comprehensive look at multiple sector demands which would provide a more complete evaluation of cumulative effects. This ultimately is intended to result in protection of areas that are essential for the resiliency and maintenance of healthy ecosystem services and biological diversity, and to maximize the ability of marine resources to continue to support a wide variety of human uses.²

Sandifer ended his presentation by noting that the National Ocean Policy specifically recognized that maintaining the health of our oceans, coasts, and the Great Lakes is essential for sustaining human health and well-being.

PROTECTING WATER QUALITY: TAMPA BAY, FLORIDA

Editors

Affiliations

Holly Greening began by noting that her presentation would be a site-specific application of some of the new information coming out about ecosystem services and how that is being incorporated into decision making in Tampa Bay, Florida. Looking at ecosystem services and habitat restoration, Greening noted that habitat restoration is mainly done for fish and birds, but recovery of coastal habitats is also important for providing human services such as carbon sequestration, nutrient reduction, air quality improvements, and aesthetics. She stated that her presentation would focus specifically on the value provided to the Tampa Bay community from nutrient reduction as a result of coastal habitat recovery and restoration over the past 20 years.

Greening provided a brief overview of Tampa Bay (see Box 8-2). She explained that Tampa Bay has seen a dramatic recovery of the water quality, underwater seagrasses, and coastal habitats over the past 20 to 25 years. This is a real turnaround that many places are not experiencing right now, she said. The amount of nitrogen removed by the restored habitat over the past 20 years in Tampa Bay is equivalent to about two medium-size advanced wastewater treatment plants in terms of the amount of nutrient reduction provided by the habitat restoration and in avoided costs.

BOX 8-2

Facts About Tampa Bay. It is Florida's largest open water estuary. The open water is about 400 square miles and the watershed is about 2,600 square miles.

In the 1970s, Greening stated, Tampa Bay was heavily polluted with an excess of nitrogen, which resulted in vast amounts of macroalgae covering the estuarine surface water. These problems were highlighted in a 60 Minutes exposé on nutrient pollution in the United States in the late 1970s. Half of Tampa Bay seagrasses were lost between 1950 and 1982 due to this excess nitrogen. The populations of macroalgae and phytoplankton covering the surface of the water blocked the sunlight and did not allow enough sunlight to reach the bottom where seagrasses were growing. Half of Tampa Bay's natural shoreline was altered during this period and 40 percent of the tidal marshes were destroyed. Some of the animal populations were negatively impacted as well; white ibis populations were reduced by about 70 percent, and fish kills were common.

Greening explained that most of the economic and environmental models from the 1970s indicated that no action could be taken to effectively recover the Tampa Bay estuary. However, the citizens were determined to do something and demanded action. In 1978, the Florida legislature required upgrades to all wastewater treatment plants in the Tampa Bay watershed (not just along the shoreline).³ The wastewater treatment standards were also advanced and upgraded, which meant reducing the amount of nitrogen in the effluent to 3 milligrams per liter of total nitrogen. Typically, there were 20–30 milligrams per liter of total nitrogen present in these wastewater treatment plants before the revised standards. As a result of this Tampa also upgraded its sewage treatment plant. Greening noted that another option was to change to 100 percent water reuse, using effluent as irrigation water in the watershed, which was only implemented in St. Petersburg.

Greening emphasized that a key factor in this process was timing. It happened shortly after the Clean Water Act was passed and funds were available to Tampa to upgrade its wastewater treatment and to St. Petersburg to install the distribution lines. So in this instance, it was not just the local citizens' action, but also the availability of funds from the Clean Water Act that allowed the wastewater treatment plants to upgrade over a 3-year period.

Tampa Bay Estuary Program

In 1990, the Tampa Bay Estuary Program⁴ was implemented and established as an intergovernmental program that uses measurable goals in science-based decisions. The policy board is made up of elected officials from the three counties in three major cities around Tampa Bay, as well the three regulatory agencies. Greening noted that one of the first things the policy board was asked to address was, “What do the citizens want from Tampa Bay? What do they want Tampa Bay to be?” One of the goals that came from a citizen survey indicated that the citizens wanted Tampa Bay to look more like it did in 1950 than it did in 1980. Greening explained that in 1950 the population was approximately one-fourth of the size as it was in 1980. Tampa Bay experienced a huge increase in population when air conditioning became available around 1950, but before then, the population growth rate was fairly flat.

In focusing on ecosystem services, the citizens identified three goals for restoring the estuary: (1) clear water, like the “good old days;” (2) better fishing; and (3) swimming without “seaweed” (macroalgae in this case). Greening noted that all three of these ecosystem services pointed to recovering underwater seagrasses by improving water quality and water clarity. The second major action taken by the policy board became a very aggressive seagrass restoration goal to restore seagrass acres to that observed in 1950. Greening again highlighted that about half of the seagrasses were lost between 1950 and 1990 due to poor water quality. The map in Figure 8-1 shows the areas where seagrasses were present in 1950 but had disappeared by 1990. Most of the losses were from the deep edge, which indicates that the light was limited and the seagrasses were retreating to the shoreline.

FIGURE 8-1

Estimated changes in seagrass cover in Tampa Bay between 1950 and 2006. NOTE Green areas show seagrass extent as mapped in 2006; red areas represent locations where seagrass occurred in 1950 but was not mapped in 2006. SOURCE: Yates et al., 2011. Data (more...)

Greening explained that the policy board established two clear steps to accomplish the seagrass restoration goal: (1) identify light requirements for seagrass and (2) identify light attenuation factors. They found that the seagrass needs to receive about 22 percent of the light that hits the surface of the water in order to be able to thrive in Tampa Bay. This amount of light is vital for the seagrasses to survive and reproduce. They also found that chlorophyll, in the phytoplankton in the water column itself, was one of the major factors associated with reducing light. Turbidity and color, but not to the same extent as chlorophyll, also had an influence on light attenuation.

Greening emphasized the goal is to maintain 22 percent light to depth were the seagrasses are present and a light attenuation of chlorophyll concentration that will allow that light to be at depth. A series of mechanistic and empirical models were developed to relate to the chlorophyll target to a specific total nitrogen load. There is a chlorophyll target for each of the four major Bay segments and a total nitrogen load associated with maintaining and not exceeding that chlorophyll target.

During the decision process with the policy board, it was made clear that any impact on phytoplankton would affect the fish population that feeds on the phytoplankton and consequently would affect the bird population, more specifically, pelicans. The challenge was to balance the two goals surrounding the amount of light for seagrass growth and the amount of phytoplankton in the water column that would support many of the fish and bird species that feed on the fish and respectively on the phytoplankton. Greening stated that at the moment, a balance has been achieved, and both the seagrass and bird populations are recovering.

Importantly, Greening noted, the policy board realized that they could not control nitrogen alone in Tampa Bay. They needed to have local governments, regulatory agencies, local phosphate companies, agricultural interests, electric utilities, and all sources of nitrogen coming to the table and agreeing to meet the long-term goals of maintaining nitrogen loads that will allow for seagrass restoration. In the mid-1990s the Tampa Bay Nitrogen Management Consortium (TBNMC)⁵ was formed, which is a public–private partnership with 40 participants that have accepted the responsibility for collectively meeting nitrogen load reduction goals. In just the past couple of years, TBNMC has also been meeting the U.S. Environmental Protection Agency (EPA) Total Maximum Daily Load (TMDL) goals, which are the total amount of pollutants that a body of water can receive in 1 day. The consortium has developed and agreed on voluntary caps on all nitrogen loads from all sources. Those caps have now been incorporated into individual permits, which means that, even with increased population growth, local counties and private entities in Tampa Bay will continue to maintain nitrogen loads at that observed in 2003. The consortium has implemented many different projects in order to meet its long-term goals (about 250 in total), some of which have focused on decreasing industrial discharges, upgrading sewage plants, improving the air quality at power plants, improving the handli g of toxic materials, improving stormwater treatment, and facilitating residential action. One interesting project, stated Greening, is where local entities and cities have implemented a residential fertilizer ban on nitrogen fertilizer during the rainy months in the summertime and also a point-of-sale restriction during that time, which have been successful.

As a result of all these different projects, Greening noted that there has been about a 50 percent reduction in the nitrogen loading between the 1970s and the 1990s in Tampa Bay, as shown on Figure 8-2. The distribution of the nitrogen sources has also changed over time. In the 1970s more than 50 percent of the nitrogen was attributed to point sources, most of which came from wastewater treatment plants. However, more difficult nonpoint sources are now the primary sources of nitrogen and are being targeted in Tampa Bay (e.g., the fertilizer ordinances that are in place)

FIGURE 8-2

Nitrogen loading in the 1990s and 1970s in Tampa Bay. SOURCE: Data from Greening and Janicki, 2006.

Water quality has also improved in the four major segments of Tampa Bay: Hillsborough Bay, Lower Tampa Bay, Middle Tampa Bay, and Old Tampa Bay. Starting in 1974, the data show that chlorophyll targets were not met. In 1984 some of the segments of the Bay began meeting the targets, but this was not consistent in all four segments until 1991. Greening stated that four major interventions contributed to this improvement:

• advanced wastewater treatment began in 1980,
• stormwater regulations were enacted in 1985,
• the Tampa Bay Estuary Program was established in 1990, and
• the Tampa Bay Nitrogen Management Consortium was initiated in 1995.

The seagrass recovery has also been progressing (see Figure 8-3). Greening explained that the goal identified by the policy board was to return to the level existing in 1950, which was approximately 40,000 acres of seagrass. The level in 1982 was about half of that observed in 1950. Slowly the seagrass has recovered; but, the biggest challenge was presented during the El Niño meteorological events of the late 1990s. During those years, Greening noted, the recovery goals were not achieved and a loss of approximately 2,000 acres of seagrass occurred. In the past few years, seagrass has recovered at a rate of about 500 acres per year and this is 500 acres of natural recovery not seagrass planting.

FIGURE 8-3

Tampa Bay seagrass recovery progress from 1982 through 2010. SOURCE: Greening, 2012. Data from Haddad, 1989.

OPTIMIZING ECOSYSTEM SERVICES IN THE FACE OF GLOBAL INCREASES IN HUMAN CONSUMPTION AND POPULATION GROWTH

Editors

Affiliations

David Tilman stated that the focus of his presentation was to describe the environmental and coastal ecosystem impacts of a rapidly expanding human population. Within 50 years, Tilman said, the global population is projected to increase by 35 percent to about 9.5 billion inhabitants. At the same time, global per-capita incomes and gross domestic product (GDP) is projected to increase 140 percent; consequently, buying power and food consumption is also projected to increase. Associated with the increase in population, income, and consumption is the human domination of global ecosystems through the increase in food and energy demands, and environmental impacts of food and biofuels on coastal waterways (Tilman et al., 2011).

According to Tilman, rising per-capita incomes around the world drive the global demand for energy and contribute to fossil fuel greenhouse gas (GHG) releases. It is estimated that global fossil GHG emissions will rise from 7 gigatons per year to about 17 gigatons per year by 2050. In parsing out this relationship, Tilman explained that per-capita agricultural demand depends on per-capita income; as income rises, diets shift to a greater demand for crop calories or protein. Tilman described the results of a forecast study he conducted with colleagues that found a simple and temporally consistent relationship between per-capita GDP and per-capita demand for crop calories or protein among seven economic groups. The study found that per-capita use of calorie and protein for the richest nations were 256 percent⁶ and 430 percent⁷ greater than use by the poorest nations.⁸ He noted that the difference between rich and poor countries is partly the result of greater meat consumption at higher incomes and low efficiency in the way some types of livestock convert crop calories and protein into edible food. Forecasts of future crop demand were developed based on the observed relationships between per-capita crop use and per-capita GDP. The analyses forecast a 110 percent increase for crop protein and a 100 percent increase for crop calories between 2005 and 2050 (Tilman et al., 2011). He added that there is a slight bias toward increasing the demand for protein in crops increasing more rapidly, such as from soybeans that are used as livestock feed and have a high level of protein.

Energy Use, Food Demand, and the Environment

Tilman emphasized that energy, food, and the environment are inextricably linked. For example, energy use is related to greenhouse emission and contributes to climate change which in turn affects storm intensity and crop growth. The increasing demand for food can increase the load of nitrogen and phosphorus fertilizers, and pesticides in coastal waters which are the home to major fisheries and sites for aquaculture. Turning to the agriculture sector, Tilman noted that producing the food needed to meet current needs releases about 32 percent of the total greenhouse gases released every year; the transportation sector contributes 14 percent. He emphasized that how demands for what is consumed are met will have a significant impact on future greenhouse gas emissions. Figure 8-4 shows the dramatic increase in total global use of nitrogen and phosphorus fertilizer, and area of global irrigated land during the Green Revolution (1960–2000). During that period, nitrogen use increased 600 percent, phosphorus 200 percent, and 80 percent more water was used in irrigation to double the global food supply. Similar trends are foreseen if the agriculture sector is expected to double food production in the next 50 years.

FIGURE 8-4

Use of nitrogen (N), phosphorus (P), and water (H₂O) to double the global food supply during the green revolution. SOURCE: Tilman et al., 2002. Reprinted with permission from Nature Publishing Group.

There are important trade-offs related to increased food production, Tilman said. Agricultural practices to increase food production can have negative effects on the ecosystem. How crops are grown and which crops are grown are major determinants of the status of coastal waters and the services they provide to society. As noted earlier, fertilizers and pesticides can increase nutrients and toxins in groundwater and surface water. Between 1940 and 2000, pesticide production increased 950 percent (Tilman et al., 2002). Practices such as land clearing for agricultural purposes can degrade the soil quality, contribute to eutrophication of aquatic habitat, and reduce biodiversity. Between 1960 and 2000, 570 million hectares were cleared for agriculture (Tilman et al., 2001). According to Tilman, if global agriculture and diets trends remain similar to those of the past 40 years, it is estimated that by 2050 global nitrogen fertilizer use will increase by 185 percent, global phosphorus fertilizer use by 140 percent, global pesticide production by 170 percent, and an additional 800 million hectares of global land would be cleared for agricultural use (Tilman et al., 2001). Further, the impact of these practices would result in 185 percent more GHG emission; global agricultural GHG emissions in 2050 would almost equal total global fossil fuel emission now (Tilman et al., 2011).

Effects of Livestock Production on Ecosystems

Turning to the environmental effects of livestock production on agriculture and coastal waterways, Tilman said the trend in livestock production is toward high-density confinement production. With more and more animals housed in large-scale facilities, the handling and disposal of animal waste is a significant problem. Manure is often collected in lagoons that can release high levels of hydrogen sulfide and other toxic gases which can contaminate surface water and groundwater with nutrients, toxins, and pathogens.

Another important aspect of livestock production is the efficiency in animal protein production and the impact on agriculture. During the period 1960–2000, global per-capita meat production increased more than 60 percent (Tilman et al., 2002). Tilman further emphasized that there are significant differences in the amount of grain it takes to produce a kilogram (kg) of edible meat or the amount of plant protein needed to produce a kg of meat. In confined animal feeding operations, for cattle, 8 kg of grain are required for 1 kg of meat (8:1) and 20 kg of edible plant protein for 1 kg of meat protein (20:1). Poultry and many types of aquaculture fish are much more efficient sources of animal protein. Shifts in the types or amounts of meat produced and consumed can cause large shifts in grain demand, and the land and agrichemicals (nitrogen and phosphorus) needed to produce it, and large shifts would also occur in the potential impacts to the ecosystem, for example from nitrogen waste.

Changes in diet and food production can lead to important changes in nitrate loading. Nitrogen and phosphorus in animal feed is excreted as waste unless it is absorbed by the animal's body. The ratio of nitrogen (often as nitrate) in waste to nitrogen in edible protein varies considerably depending on the efficiency of the animal. The approximate ratio of nitrogen in waste to that in edible protein in cattle is about 19:1, for poultry it is about 3:1, and for some aquaculture fish it is about 2:1. Thus, per kilogram of edible protein, cattle production leads to much greater amounts of nitrogen excreted as waste than does fish or poultry production, Tilman said.

A number of countries have begun to develop strategies to increase nitrogen efficiency in the agriculture process such as applying the appropriate amount of fertilizer at the appropriate time during the growing season of the crop. For example, the European Union (EU) had water quality problems related to nitrogen loading in its coastal waters. They imposed laws requiring farmers to obtain permits to justify the purchase of nitrogen. As a result, there was a one-third decrease in amount of nitrogen being applied to the soil. Crop yields, however, contin ed to increase even though less nitrogen was applied; this is because nitrogen was applied more effectively, Tilman explained. More importantly, improvements in water quality measures were seen; nitrogen loading in the EU coastal waterways was significantly improved.

Tillman described a strategy to reduce the use of pesticides in agricultural production. In China, scientists discovered that they could eliminate the need to apply a toxic fungicide to rice by planting alternating rows of two different varieties of rice. One of the varieties was resistant to a major rice fungal disease. Its presence so greatly decreased disease incidence that fungicide use could be eliminated. This increased productivity and reduced human exposure to the pesticide.

In summarizing the presentation, Tilman reiterated that to meet human needs for food crop production there is an increased use of land, nitrogen and phosphorus fertilizers, and pesticides which affect coastal waterways and ultimately the oceans that also contribute to food production. The primary effects are related to nitrogen and phosphorus and GHGs that affect the atmosphere and the open oceans that provide fish and other seafood. This interrelated system is seen in Figure 8-5.

FIGURE 8-5

Food demand links to land and waters. SOURCE: Tillman, 2012.

A system approach is needed to address the human demand for food and to lessen the impact of agriculture on the environment, Tilman said. One potential strategy is a dietary shift to higher-efficiency land animals, which would decrease nitrogen and GHG emissions. Another strategy is to increase fertilizer efficiency, which would also decrease nitrogen and GHG emissions. Implementing environmentally wise ways to better manage fisheries to increase the amount of fish and seafood to harvest and to include in the diet is another strategy. Moderate successes implementing all of these strategies would go far to meet the current and future human demand for food in ways that would help preserve the health of coastal waterways and oceans.

DISCUSSION

Lynn Goldman noted that the decision to meet the EPA TMDL goals in Tampa Bay presented by Greening is an effective way to address a problem like nitrogen, which has multiple sources that all impact one resource. She asked Greening about how population growth is being approached in Tampa Bay because growing communities will likely put out more nitrogen despite the fact that there have been improvements at the wastewater treatment plants and with fertilizer regulations. Greening explained that the Florida Department of Environmental Protection accepted the science behind the EPA TMDL goals for nitrogen management and allowed the public–private consortium to define how the goals would best be allocated throughout Tampa Bay. This resulted in much buy-in from the all the different partners representing point sources and nonpoint sources in the area. In terms of managing growth, Greening said, the Tampa Bay Estuary Program is looking at implementing projects that can offset new growth. In addition, she said, each of the permitted point and nonpoint sources are required to address this issue. If a permitted source needs to have an additional allocation beyond the 2003 cap, then it needs to show a nitrogen reduction somewhere else. Greening explained that some are offsetting the growth with additional stormwater treatment, fertilizer ordinances, and transfers of reduced emissions from the electric utilities in the watershed.

Richard Jackson from the University of California, Los Angeles, noted that the citizen involvement described in Tampa Bay supports the notion that people really want clean water. From a public health standpoint, he said, a public wastewater treatment system has tremendous benefits over independent septic systems because it is maintained and managed to recapture the wastewater. He asked Greening to comment. Greening stated that in Tampa Bay there are pockets of septic systems but that most of the residential areas are now on a central sewage system. One of the major sources of bacteriological contamination remains wastewater treatment package plants associated with trailer parks and older communities, she said, and those remain a target for both nitrogen and other public health reasons. Greening went on to say that in Tampa Bay approximately 70 to 80 percent of the wastewater treatment plants now have at least some recaptured water. One of the issues is that the piping to get this out to residential areas is quite expensive. As noted in her presentation, the reason that St. Petersburg was able change to 100 percent water reuse was a result of funding available from the Clean Water Act; without these funds this may not have been possible because of the associated infrastructure costs. Edward Laws from the Louisiana State University School of the Coast and Environment joined the discussion and noted that wastewater treatment plants are often not located with the idea of wastewater reuse in mind. This is now starting to change with resort areas investing in wastewater reuse for golf course irrigation but has not been a focus in other localities.

Laws then highlighted that the Chesapeake Bay Area has struggled to meet the goal for bay grass recovery and asked Greening to comment on why this program has been problematic. Greening stated that one main difference with Tampa Bay is that the majority of the population sees the bay nearly every day, which differs from the watershed placement in the Chesapeake involving multiple jurisdictions and populations that never see the bay. Because of this, the public support is much stronger in Tampa. She noted that another difference is scale; the Chesapeake Bay is much larger in size than Tampa Bay, which more closely resembles the size of Upper Chesapeake Bay. Greening explained that there have been successes in the Chesapeake Bay, but because of the scale issue they have not had the same impact as seen in Tampa. Additionally, the ecosystem services that benefit health and well-being have not been adequately valued in the Chesapeake Bay.

Laws asked Tilman to comment on the use of groundwater for irrigation, which is not sustainable in parts of China or the United States. Tilman noted that many aspects of global food production are not really sustainable and water is one of the big issues. For instance, about 11 percent of the land area in China is suitable for agriculture and they are utilizing about 13 percent at this time, including vast areas of dry land that require substantial amounts of groundwater that is not sustainable. In the United States, aquifers for corn production in the Midwest are not being recharged at the same rate as they are being drawn down, which is also a sustainability issue. There are many nations around the world that have low yields but good climate, but the farmers do not have the knowledge to do modern farming and may be subject to political unrest. Tilman stated he hopes these poorer nations of the world with large yield gaps can find a way to have the lands become more productive, which could potentially meet 70 percent of the food demand that is coming, without adding additional irrigation. So there are places in the world, he said, where we could have sustainable agriculture but these nations are lacking the knowledge, the capital, and the infrastructure that is required.

Dennis Devlin from ExxonMobil asked Tilman to comment on whether incorporating genetically modified organisms (GMOs) in his food production analysis would make a difference in the environmental impacts. Tilman noted that some GMOs provide a benefit if they can be grown without pesticides, but on the yield side, the GMOs are not providing greater yields compared to non-GMOs and in some instances provide lower yields, which can add costs. So currently, he said, incorporating GMO crops does not make much of a difference. Tilman went on to say that developing crops to remain ahead of diseases will continue to be a long-term issue and genetic modification will likely be an important tool as it has the potential to allow for the movement of many more genes to keep crops resistant to new pathogens.

REFERENCES

• Birch MBL, Gramig BM, Moomaw WR, Doering OC, III, Reeling CJ. Why metrics matter: Evaluating policy choices for reactive nitrogen in the Chesapeake Bay watershed. Environmental Science and Technology. 2011;45:168–174. [PubMed: 20853823]
• Greening H. Protecting water quality: Tampa Bay, Florida; Presentation at the Institute of Medicine workshop on Understanding the Connections Between Coastal Waters and Ocean Ecosystem Services and Human Health: Basic Services, Valuation and Resiliency; Washington, DC: 2012.
• Greening H, Janicki A. Towards reversal of eutrophic conditions in a subtropical estuary: Water quality and seagrass response to nitrogen loading reductions in Tampa Bay, Florida, USA. Environmental Management. 2006;38(2):163–178. [PubMed: 16788855]
• Haddad KD. Habitat trends and fisheries in Tampa and Sarasota Bays. (NOAA Estuary of the Month Seminar Series 11). Washington, DC: National Oceanic and Atmospheric Administration; In Tampa and Sarasota Bays: Issues, resources, and status and management. 1989:113–138.
• IOPTF (Interagency Ocean Policy Task Force). Final recommendations of the Interagency Ocean Policy Task Force. Washington, DC: White House; 2010. (White House Council on Environmental Quality).
• Kildow T, Colgan CS, Scorse J. State of the U.S. ocean and coastal economies. 2009. [August 14, 2013]. (National Ocean Economics Program). www​.oceaneconomics.org.
• Roeder E. A range of cost-effective strategies for reducing nitrogen contributions from onsite sewage treatment and disposal systems. Bureau of Onsite Sewage Programs. Tallahassee, FL: Florida Department of Health; 2007.
• Russell M, Greening H. Estimating benefits in a recovering estuary: Tampa Bay, Florida. Estuaries and Coasts. 2013 [CrossRef]
• TBEP (Tampa Bay Estuary Program). Charting the course: The comprehensive conservation and management plan for Tampa Bay. St. Petersburg, FL: TBEP; 2006.
• Tilman D. Optimizing ecosystem services in the face of global increases in human consumption and population growth; Presentation at the Institute of Medicine workshop on Understanding the Connections Between Coastal Waters and Ocean Ecosystem Services and Human Health: Basic Services, Valuation and Resiliency; Washington, DC: 2012. [PubMed: 24830061]
• Tilman D, Fargione J, Wolff B, D'Antonio C, Dobson A, Howarth R, Schindler D, Schlesinger WH, Simberloff D, Swackhamer D. Forecasting agriculturally driven global environmental change. Science. 2001;292(5515):281–284. [PubMed: 11303102]
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• Tilman D, Blazer C, Hill J, Befort BL. Global food demand and the sustainable intensification of agriculture. Proceedings of the National Academy of Sciences of the United States of America. 2011;108(50):20260–20264. [PMC free article: PMC3250154] [PubMed: 22106295]
• Yates KK, Greening H, Morrison G. Integrating science and resource management in Tampa Bay, Florida. U.S. Geological Survey Circular. 2011;1348:1–280.

Footnotes

1

Executive Order 13547, Stewardship of the Ocean, Our Coasts, and the Great Lakes. 2010. Available at: http://www​.whitehouse​.gov/the-press-office​/executiveorder-stewardship-ocean-our-coasts-and-great-lakes (accessed July 15, 2013).

2

Executive Order 13547, Stewardship of the Ocean, Our Coasts, and the Great Lakes. 2010. Available at: http://www​.whitehouse​.gov/the-press-office​/executiveorder-stewardship-ocean-our-coasts-and-great-lakes (accessed July 15, 2013).

3

Grizzle-Figg Act, Section 403.086, Florida Statutes.

4

Information on the Tampa Bay Estuary Program is available at: http://www​.tbep.org (accessed September 9, 2013).

5

Information on the Tampa Bay Nitrogen Management Consortium is available at: http://www​.tbeptech.org (accessed September 9, 2013).

6

Group B: Argentina, Chile, Greece, Israel, Italy, Malaysia, Mauritius, New Zealand, Portugal, Saudi Arabia, South Korea, Spain, Trinidad and Tobago, Uruguay, and Venezuela.

7

Group A: Australia, Austria, Canada, Denmark, Finland, France, Germany, Ireland, Japan, The Netherlands, Norway, Sweden, Switzerland, United Kingdom, and United States.

8

Poorest nations. Group F: Burkina Faso, Eritrea and Ethiopia, Gambia, Guinea, Haiti, Kenya, Madagascar, Malawi, Mali, Nepal, Rwanda and Burundi, Sudan, Tanzania, Togo, Uganda, Zambia, and Zimbabwe. Group G: Central African Republic, Chad, Democratic Republic of the Congo (former Zaire), Niger, and Sierra Leone.