Mapping the Mangroves - MWL


In previous lessons we have established the fact that mangrove estuaries are a key coastal habitat that acts as a connection between terrestrial and marine environments. They serve as nurseries for marine life, rookeries for birds, and a rich nutrient sink in the nutrient poor tropics. In addition, mangroves act as an important stabilizing mechanism against erosional forces in coastal areas.

So why would such a strategic habitat be destroyed and why are there not better protective measures in place? We will examine these questions in two stages. First we will explore the impetus behind mangrove estuary destruction, and second we will investigate valuation strategies to recognize estuary worth.

Hot, humid, buggy, and a bit forbidding are four adjectives commonly used to describe a visit to an estuary. These terms are accurate, and if a visitor is not able to get past them to see the deeper, richer aspects of an estuary, they may walk away with little appreciation, understanding, or respect for this ecosystem. A lack of understanding of a mangrove estuaries role within the environment sets the stage for its modification for other purposes, and sets in motion a whole set of degrading scenarios.

Mangrove estuaries are modified for a number or reasons, most of which centers around their coastal location. The following is a series of examples:

  • Hotel and resort development- Cutting and filling of mangrove estuaries results in prime coastal lands for hotel and resort development. This type of development and subsequent tourism, serves as a cornerstone to many countries economic viability.
  • Marina and harbor development- Cutting and dredging of mangrove estuaries results in prime locations for marina and harbor development. Mangrove estuaries tend to be found in sheltered areas with water channels, two key characteristics for these types of projects. Once again this type of development builds economic viability.
  • Aquaculture sites- Cutting and dredging of mangrove estuaries results in prime locations for aquaculture ponds for shrimp and fish. The flat, protected natures of estuaries with natural currents are key characteristics for successful aquaculture sites. Aquaculture is an important industry in the economics of many poorer developing tropical countries.

These types of development lead to a series of secondary degrading effects on the environment. The following is a series of examples:

  • Increased erosion- Mangrove root systems are integral in stabilizing sediments, controlling erosion in flooding scenarios, and protecting shoreline from wave action and rising sea levels. Loss of mangrove root systems results in increased erosion.
  • Pollution- Contaminated runoff, sewage seepage or outfalls, aquaculture waste (antibiotics, animal waste, food waste) are three sources of pollution that adversely affect developed mangrove estuaries. They can lead to toxic scenarios for estuary organisms, such as eutrophication. These pollution sources degrade mangrove habitats.
  • Habitat loss- Destruction of the mangroves results in the loss of a cornerstone species, leading to a collapse of a habitat and loss of species diversity. Because mangroves estuaries link other ecosystems together, this degradation becomes cascading in nature.

Other developmental processes include:

  • Harvesting of wood, primarily by subsistence based populations.
  • Oil exploration and extraction. The Nigerian Delta is an example.

There is financial gain in developing estuaries, which couples with economic progress of an area or country. Together these factors are powerful incentives to develop mangrove estuaries. But this is a one sided perspective and can be balanced by establishing a monetary valuation on estuaries. In this respect, we now have a counter to development that is being expressed in common language. This facilitates discussion and allows for conscientious decision making to take place. The ability to place a value on an estuary in monetary terms becomes an important way of expressing its worth and aiding in its protection.  We’ll examine valuation processes in the teaching summary section.


  • Students will recognize reasoning behind mangrove estuary destruction.
  • Students will develop valuation strategies to illustrate importance and aid in protective measures.

Teaching Summary

There are a number of different approaches and techniques that can be used to establish a valuation on an estuary. Consider looking at your specific area and assessing the resources that are available, to aid in establishing your approach to the activity. For example, if you were to look at the estuary from the perspective of coastal protection, the following would be items to consider:

  • government zoning guidelines
  • historic weather patterns and phenomena
  • insurance policy standards for valuation purposes
  • environmental engineering groups assessments of the estuary and its protective benefits

Once a valuation has been established, using the information in debate or assessment of development projects allows one to see the data’s value and continue to refine the valuation process. The activity outlined below uses tourism to establish a valuation on an estuary.

Mangrove Estuary Valuation Model Based on Tourism

      Estuary Name and Location –

      Features -

      Key Income Production in Area –

      Estuary Relation to Area Economics –

      Estuary Valuation Parameters –

      Calculations for Estuary Valuation –

      Debate Scenario of Estuary Development –

Sample Data

Estuary Name and Location – Tamarindo Estuary                Guanacaste Costa Rica

Features – Largest estuary in Costa Rica, potential world heritage site.

Key Income Production in Area – Tourism centered on Surfing, Fishing, and Nature Observation

Estuary Relation to Area Economics -

  • Fisheries related - Nursery for marine fishes and invertebrates, including important populations of sportfish such as snapper, snook, and roosterfish, as well as forage fish production.
  • Surf Related – Sand bar formation improving wave quality, clean water flow, beach formation and stabilization, and standup paddle boarding in estuary.
  • Nature Observation – Kayak and motorboat tours, bird watching

Estuary Valuation Parameters –

  • Most people do not visit Tamarindo specifically for nature observation, therefore its financial contribution will be based on monies spent on excursion exploring the estuary.
  • Tamarindo is a specific destination for surfers and sport fishermen. Without the estuary this destination wouldn’t exist, or would be degraded to the point that tourists would not come. Therefore total monies spent by a tourist visiting the area can be used in valuing the estuary
  • Tamarindo has a low season / high season with relationship to tourism, that will be taken into account in calculations.

Calculations for Estuary Valuation –

High Season  (121 days) (December/January/February/March)Average expenditure of client per dayTotal Expenditure
Number of surfers per day - 50$125/day$756,250
Number if sport fisherman per day - 30$ 250/ day$727,500
Number of excursions per day - 40$ 35 / excursion$169,400

Total - $1,653,150

Low Season  (244 days)  (April/May/June/July/August/September/October)Average expenditure of client per dayTotal Expenditure
Number of surfers per day - 35$100/day$854,00
Number if sport fisherman per day - 20$ 210/ day$1,024,800
Number of excursions per day - 20$ 25 / excursion$122,000

Total - $3,000,800

  • Total monies spent directly related to a healthy, functioning estuary on a yearly basis - $4,653,950

Debate Scenario of Estuary Development – Tamarindo estuary faces development pressures on its fringes from housing and commercial centers. Outline how this development will effect the estuary, and how that will in turn effect revenue generated by the estuary. What role do these finding play in determining the course of action to be taken in regards to development planning?


Assessment Questions


  1. What factors may contribute to error in the calculations?
  2. What role should a government play in decision-making processes of this type?
  3. How could you factor in long-term benefits to a society with regards to protective measures benefitting the estuary?


  1. Concerns may include: How to factor tax, expanding cost calculations to include airfare, etc.…
  2. Answers will vary; key points may include cooperation aspects amongst concerned groups, how vested government is in outcomes.
  3. Answers will hinge on how you value health of an ecosystem, and what it means to future generations.
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