The value of seagrasses, as perceived by humans, changes in time and place. In the past, seagrasses have been valued because the plants yielded material for various practical purposes. Dried seagrass material was, for example, commonly used as housing insulation and to thatch roofs in rural coastal areas in Europe and the UK.

One of the major beneficial properties of seagrass as insulation was that it was non-flammable, because of its high silicon content, and that it was flea-proof. Current appreciation of seagrasses concerns not as much the direct use value, but instead the services that seagrass meadows provide to overall functioning of costal zone systems. Nevertheless, in poor coastal populations of the developing world, seagrasses still are important sources of food and income.

Seagrass meadows enhance the biodiversity and habitat diversity of coastal waters by their mere existence and by creating suitable habitat for algae and faunal organisms. They also support the production of living marine resources: they are nursery and foraging areas for a number of commercially highly important fish and shellfish species.

Seagrass meadows improve water quality by reducing particle loads in the water and absorbing dissolved nutrients. They stabilize and bind sediments with their roots and web like growth form. This is a very important character for costal protection as it prevents erosion and shoreline regression.

Seagrasses plays a significant role in global carbon and nutrient cycling. Seagrass biomass, together with that of long-lived macroalgae, is an important sink for carbon in the ocean, and most of the biomass produced by seagrasses ends up as refractory detritus. As a result, the quantity of seagrass carbon available to be stored in the sediments represents about 12% of the total carbon storage in the ocean as a whole, even though the production of seagrasses only represent a small percentage (1%) of the total oceanic production.

The importance of seagrass meadows to humans is especially obvious in tropical coastal communities because of their close association with the adjacent marine ecosystems. In many areas people are directly dependent on the goods and services of the seagrass beds. For example in Kenya, Tanzania and the Philippines many subsistence (and even commercial) activities are related to seagrasses. Seagrasses are used as fishing and collection grounds and even as direct food source sometimes! The leaves of the tiny Halophila spp. can be eaten like salad and the seeds of Enhalus acoroides are used for flour. In many of the rural coastal communities in developing countries seagrass associated fish is the basis for protein provision. Typical examples are "seagrass parrot fish" Leptoscarus vaigiensis, "rabbit fish" Siganus sutor, a variety of "small emperors" Lethrinidae and "snappers" Lutjanidae.