Rachel Carson’s “Silent Spring,” first published in 1962 was the awakening of the world to the environment in which we all live and the problems with that environment. It was also the beginning of awareness for certain specific ecosystems such as salt marshes, mangrove swamps, sea grass beds, and coastal lagoons. Collectively many of these coastal areas have become known as the “Blue Forest.” The blue forests of a region provide a number of functions important to humans which we can refer to as ecosystem services. Ecosystem services are the benefits that people derive from the environment, whether they are tangible goods or intangible functions.
Coastal marine areas are critically important to the global carbon cycle. This cycle is the main factor affecting what is commonly referred to as global climate change. Our coastal environments, and the marine ecosystems they support, are natural carbon sinks. In fact, healthy coastal ecosystems represent the largest active carbon sink on Earth. Scientists recognize that some coastal and marine ecosystems, including tidal marshlands, mangrove ecosystems and seagrass meadows, play a natural role in absorbing carbon from the atmosphere. Healthy natural coastal ecosystems are also critical to the livelihoods and food security of millions, and to the conservation of regional biodiversity. The continuing degradation of our coasts and loss of these ecosystems decreases the natural capacity of our oceans to perform these functions.
The “Blue Forest” of mangroves, sea grass beds and saltmarshes provide food from fish, they provide exceptionally high biodiversity habitats, they shelter villages and towns from storms, and they are also significant for our global climate by storing and sequestering carbon. In fact blue forest ecosystem services can be divided into four broad categories: 1) provisioning, 2) regulating, 3) supporting, 4) and cultural. Provisioning services are familiar to most people as they represent the goods – such as fish and other seafood, minerals, and energy – that are extracted from the environment. Regulating services include carbon sequestration, weather regulation, and coastal protection from storms and hurricanes. Supporting services are the foundational functions such as photosynthesis, nutrient cycling, and basic soil, sediment and sand formation. Cultural services represent the spiritual, educational, and recreational enjoyment derived from the coastal environment. While many of the services are non-extractive, non-market goods, they underpin our economies and support our well-being.
The blue forests of our coastal seas also have been referred to as “Earth’s other lung!” For example, new research has demonstrated that sea grass beds can store up to 83,000 metric tons of carbon per square kilometer, mostly in the soils below them. In comparison, a typical terrestrial forest stores around 30,000 metric tons per square kilometer, most of which is in the form of wood. Fifty seven percent (57%) of atmospheric carbon captured by living organisms is captured, in fact, by marine organisms, and of this between 50 and 71% is captured by the ocean’s vegetated habitats including mangroves, salt marshes, sea grasses and seaweed, the so-called blue forests, which cover less than 0.5% of the seabed. These key coastal habitats represent an important opportunity for ecosystem-based climate mitigation (known as ‘blue carbon’) which also preserves the essential ecosystem services of these habitats.
Mangroves for example, are keystone coastal ecosystems providing numerous environmental services and critical ecological functions, affecting both upland and oceanic resources. These services include protection from storms and tsunamis, regulation of water quality, breeding and rearing habitats for many species of fish and shellfish, important sources of wood and other forest products for local populations, and biodiversity, including habitats for many rare and endangered species. These ecosystems are a source of nutrients and energy for adjacent habitats including sea grass and coral reefs, and are also valued for aesthetics and ecotourism. As much as 75% of all tropical commercial fish species spend part of their lifecycle in mangroves. Mangroves have been used for centuries by indigenous peoples for wood, thatch, medicines, dyes, and fish and shellfish. Mangrove forests are also among the major carbon sinks of the tropics. Perhaps the least investigated, yet critically important, ecosystem service of mangroves is that of carbon storage. Mangrove carbon pools are among the highest of any forest type. For example, ecosystem carbon pools of mangroves in the Indo-Pacific region are more than twice those of most upland tropical and temperate forests. A great proportion of this pool is below-ground in organic rich soils which are highly susceptible to releasing significant volumes of greenhouse gases if disturbed by land-use or climate change.
Sea grass beds, similarly, sequester carbon, cycle nutrients, support fishery yields, reduce turbidity, and provide coastal protection functions. Moreover, the productivity of mangroves, salt marshes, and coral reef ecosystems are also mutually enhanced by sea grass beds as fish move among the different habitats for food and refuge and during different life stages. While each of these ecosystem functions may be quantified individually, their production is tightly linked. The ability of each habitat to provide services is also interdependent on the health of connected systems whether they are marine, coastal, freshwater or terrestrial. This linkage implies that any impacts, whether positive or negative, on one ecosystem service or habitat could have cascading impacts on the sustainability of other ecosystem services and habitats.
The marine coastal ecosystems of Belize provide a number of services and functions that are increasingly being degraded and losing their ability to provide fundamental utilities upon which human well-being depends. Human activities are threatening these coastal ecosystems. Mangrove forests are threatened by land-use and/or land-cover change, as well as global climate change. Rates of mangrove deforestation and conversion are among the highest of all tropical forests, far exceeding rates in upland forests. Globally, land conversion has resulted in the loss of more than 35% of mangroves during 1980–2000. Global climate change impacts that may exacerbate losses include sea-level rise, changes in tropical storm (cyclone) intensity, and changes in stream flows that discharge into mangroves. Shrimp farming has been a huge driver for mangrove deforestation, as has the development of land near the coast for human habitation. When lost, these coastal ecosystems (mangroves, tidal marshes, and sea grasses) stop sequestering carbon and release what they have stored, thus becoming new sources of carbon emissions. Recently some shrimp farming operations have changed their approach to mangrove deforestation, instead protecting the mangroves. But development for coastal housing continues unabated.
Recently the scientific community has become increasingly aware that coastal ecosystems actually contain much more carbon per unit area than many terrestrial ecosystems; giving them additional value and significance in the global climate challenge. Mangroves are quite different from upland forests in both composition and structure. The presence of stilt roots or pneumatophores is an obvious difference. In addition, understory vegetation and a well-developed floor litter are usually absent (crabs are usually extremely efficient consumers of fallen leaves in mangroves). Because of numerous differences in the structure and environment of mangroves compared to upland forests, approaches to quantifying their composition, structure, carbon stocks and status are different, but none the less needed to be able to monetize their value to humans.
The value of blue forests to coastal communities is matched only by the extraordinary amount of carbon stored in their biomass and sediments, known as blue carbon. Blue forests represent only 3% of global terrestrial forest cover, yet 55% of all carbon captured in the world is blue carbon. Linking coastal ecosystems to the role they play in mitigating climate change through carbon finance can incentivize their protection and safeguard the livelihoods that they support. However, blue carbon has not been fully included in emissions accounting or protocols, and blue carbon standards for carbon markets are still in their infancy.
Because of the values of, and threats to, mangroves, there is great interest in mangroves’ potential value in carbon mitigation programs and other financial incentives tied to conservation of standing forests. Belizean officials should investigate some of these programs for developing strategies to reduce global greenhouse gases by receiving compensation for avoiding mangrove deforestation or forest degradation. In addition Belize programs should be developed that entail a broader framework that could include compensation for forest conservation, sustainable forest management, and enhancement of carbon stocks. Because of their large ecosystem carbon stocks, as well as the numerous other critical ecosystem services they provide, mangroves are potentially well suited to these climate change mitigation strategies.
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