Marine Systems

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Notes to Table 2

Marine Systems

Marine systems perform many key functions, from regulating the biosphere to the processing of elements into countless configurations of food webs, sediments, and water column forms. We have focused here on a subset of important functions to which we felt some value could or should be assigned. These include the development of food webs leading to harvestable food and raw materials, nutrient cycling, and the role the ocean plays in regulating gas exchanges with the atmosphere. Where possible, we tried to provide a range of value estimates, recognizing that different sets of assumptions can result in wide divergence in the assigning of value. For food and raw materials production, market values were determined from the best available sources. For biogeochemical fluxes, we attempted to compute replacement values if the natural ecosystems were no longer able to supply the particular service. Finally, we used estimates of real estate price differentials (hedonic pricing) as a surrogate for the service that marine ecosystems perform in enhancing the cultural fabric of society.

Some important values are more difficult to quantify than even the difficult evaluations we did carry out, and for this reason were left out of the current analysis. This includes the assessment of value of biodiversity as such and the services of higher trophic levels as controllers and amplifiers of ecosystem processes. Many of these services simply have no convenient economic analog (e.g., what is the replacement value of a species, or a species assemblage? surely it depends on the species and the assemblage). While acknowledging that these services are probably important, we left them out for now.

Open Oceans

1. Gas Regulation

Oceans play a critical role in the balance of global gas regulation. Oxygen and carbon cycles are intimately linked, as are N, P, and S cycles. We focused on the role of the oceans as (1) a sink for CO2, since transfers of CO2 to the atmosphere result in increases in greenhouse warming, and (2) a producer of methane, a secondary greenhouse gas.

A. Two estimates of CO2 absorption by the world’s oceans:

1) Schlesinger (1991) estimated net storage of organic C in marine sediments at ca. 0.1 x 1015 g C y-1, which = 0.366 x 1015 g CO2 y-1

2) Butcher et al. (1992) discuss a simple model of the global carbon cycle, in which the net input of C to the oceans from the atmosphere is 1 x 1016 mol y-1, which = 44 x 1016 g CO2 y-1.

Obviously there is a large discrepancy between these estimates. On page 309 of Schlesinger, net inputs of C to the oceans is 2.4 x 1015 g C y-1, and the atmospheric pool is 720 x 1015 g C. Thus, if the ocean were to cease absorbing the net amount of C, it would take 300 yr to double the C pool in the atmosphere, which would lead to an increase of 3 °C. Fankhauser and Pearce (1994) estimated the economic cost of CO2 as $20.4 per MT carbon. Using the most and least conservative estimates of net removal of CO2 as C in marine sediments, we arrive at:

a) 0.1 x 1015 g C y-1 = 100 x 106 MT y-1 / 32200 x 106 ha = 0.003 MT C ha-1 y-1

0.003 MT C ha-1 y-1 x $20.4 MT-1 = $0.61 ha-1 y-1

b) 1 x 1016 mol C y-1 = 12 x 1010 MT C y-1 / 32200 x 106 ha = 3.73 MT C ha-1 y-1

3.73 MT C ha-1 y-1 x $20.4 MT-1 = $76 ha-1 y-1

The average of this low and high estimate is $38.3 ha-1 y-1

B. Methanogenesis by the world’s oceans

Schlesinger (1991) estimated: 10 x 1012 g CH4 y-1 = 7.5 x 1012 g C y-1 . Fankhauser and Pearce (1994) also estimated the price of CH4 as a greenhouse gas as $110 per MT CH4. This yields: 10 x 106 MT CH4 y-1 x $110 MT-1 / 32200 x 106 ha = $0.03 ha-1 y-1. This is negligible compared to the CO2 benefits.

8. Nutrient cycling.

Oceans are critical in maintaining global nutrient cycles. Here we focus only on nitrogen (N) and phosphorous (P), the major "macronutrients". While we recognize that other macronutrient cycles (eg. sulphur, potassium, silica) and a host of micronutrients are also important, we have ignored them in the current study, implying a conservative estimate. The value of the oceans for global N and P cycling derives from their role as N and P sinks. If the oceans were not there, we would have to recreate this function by removing N and P from land runoff and recycling it back to the land. We took two approaches to evaluating this function.

We assumed that the oceans and coastal waters are serving as sinks to all the world’s water that flows from rivers, and that the receiving marine waters provide a nutrient cycling service. If we assume that roughly one-third of this service is provided by estuaries (Nixon et al. 1996 in press) and the remainder by coastal and open ocean, (assume 1/3 by shelf and 1/3 by ocean), then the total quantity of water treated is 40 x 1012 m3 y-1. Replacement costs to remove N and P were estimated at $0.15 - 0.42 m-3 (Richard et al. 1991 as quoted in Postel and Carpenter 1997). Thus, the replacement cost for each biome’s (1/3) contribution to the total value is $2.0 x 1012 - $5.6 x 1012 By hectare, the value for ocean (32200 x 106 ha) is then $62.1 - 174 ha-1 y-1.

11. Biological Control

See data (Note 13, below) on estimates of fish production. We assumed that the control function of upper trophic levels is at least 30% of the value of the catch (even though the production in those trophic levels is 3-5 times the catch) (Source: R. D'Arge, personal communication), yielding an estimate of $5 ha-1 y-1

13. Food production

The following table summarizes data on global fish production, catch and potential catch for both upwelling and open ocean areas.


Ecosystem Area Pr.Prod Fish Prod. Fish Catch Potential Catch

(108 ha) (g C m-2 y-1) (g m-2 y-1) (g m-2 y-1) (g m-2 y-1) (MT ha-1 y-1)



Upwelling 5 225 23.2 3.541 4.97 0.0497

Oceanic 332 57 2.462 0.256 0.59 0.0059


Source: Houde and Rutherford 1993 (except for footnotes).

These numbers are probably as good as we can get, and are probably within a factor of 5. Average 1993 price, calculated from imports and exports of total marine fish catches (by continent) is $2.28 kg-1 (± $1.18 s.d.) (FAOSTAT Database Collections (on WWW). The value of fish catches, in $ ha-1y-1, is assumed to be the average price times the quantity (see main text for a discussion of this assumption). Thus for the total potential catches in these biomes, the value is:


Ecosystem Area Potential Catch Value (MT x $2280/MT)

(108 ha) g m-2 y-1 MT ha-1 y-1 $ ha-1 y-1


Upwelling 5 4.97 0.0497 113

Oceanic 332 0.59 0.0059 13.5

Area weighted average (upwell + open) $15


14. Raw materials

Considering only one product, i.e. the formation of limestone in shallow ocean basins (and then “spreading” it out over the entire ocean floor):

Estimate #1. Source: Holland 1978: 0.5 mg cm-2 yr-1 = 5 g m-2 yr-1 (from a study by Broecker and Takahashi 1966 on Bahama Grand Banks)

Estimate #2. Source: Schlesinger 1991. 1.5 x 1015 g y-1 (taken from Wollast 1981.) divided by the area of ocean = 332 x 1012 m2 = 4.52 g m-2 y-1 .

These estimates are roughly equivalent to 0.05 MT ha-1 y-1. The market price of limestone (f.o.b., determined by telephone interviews with quarry managers) is approximately $10 MT-1. If we assume that 84% of the price covers capital and labor costs, then the ecosystem “value added” amount is worth $1.60 MT-1. The estimated value of oceans for limestone production is: 0.05 MT ha-1 y-1 x $1.60 MT-1 = $0.08 ha-1 y-1 .

17. Cultural Values

As reflected in literature, song, education, and other ways, humans place tremendous value on coastlines and oceans. One tangible economic manifestation of the cultural value placed on these ecosystems is the willingness to pay for real estate in proximity to estuaries and oceans, compared to the price of comparably sized inland real estate (all other things being equal). Price differentials between inland and waterfront properties in a rich and a poor part of the United States were collected. We then assumed that this differential would be valid for the world's wealthy nations (developed) and would be 100 times lower in the remainder of the world's nations.

California: $0.5 x 106 / 0.046 ha = $10.8 x 106 ha-1

Alabama: $0.1 x 106 / 0.186 ha = $0.54 x 106 ha-1

Coastline: “Developed”: 194,435 km

“Undeveloped”: 284,795 km

Assume that the value extends from the shoreline and back 0.5 km from shore. Then the area of real estate is

Developed 9.7 x 106 ha

Undevel. 14.2 x 106 ha .

Using the spread in real estate price differentials above, and assuming prices are 100 times less on undeveloped lands, we obtain

Developed values (total): $5.24 to $105 x 1012

Undeveloped: $0.077 to $0.158 x 1012

Total value: $5.32 to 105.2 x 1012

If we divide this value by the area of all marine ecosystems except the open ocean (4102 x 106 ha) and amortize over 20 years, the areal values become $65 to $1282 ha-1 year-1 for estuaries, shelves, coral reefs and seagrass ecosystems. If we instead divide this value by the total marine area (36.302 x 106 ha), then the annual value "flow" is $7 to $145 ha-1 y-1 or an average of $76 ha-1 y-1

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