Agroforestry Agriculture 02 January 2022

Intertidal zone ecosystems: definition, zones, and threats

An intertidal zone is the area of shoreline between high tide and low tide. It is underwater at high tide and exposed to air at low tide, and it includes rocky shores, sandflats, and mudflats. Because the tide advances and recedes twice a day, the environmental conditions are constantly changing, so the plants and animals that live there cope with tides, waves, and drying out.

Thus, the intertidal zone ecosystem is unique, especially as it is designed to withstand these variations. However, any disruption to the ecosystem puts it under threat climate change-related impacts are having a large impact, along with threats from tourism, pollution, and coastal development.

The tides in the intertidal zone

A typical intertidal zone ecosystem consists of various animal and plant types, including barnacles, mussels, seaweed, and sandworms, which thrive within the zone. However, other species also utilise the zone temporarily, either for food or as a seasonal habitat these include fish, shrimp, seals, and migratory birds.

In these ecosystems, the tide advances and recedes twice a day, meaning that the environment undergoes rapid variation in temperature, moisture, and salinity. It is also frequently hit by strong winds and waves.

Organisms have therefore evolved to be suited to this harsh environment. For example, barnacles and mussels fill their shells with seawater to survive the low tide. Fish and shrimp species take refuge during low tide in any rockpools, or pools of water formed on expanses of mud and sand.

The intertidal zone ecosystem sees greater biodiversity in different parts of the zone, depending on how much of the day an area is covered in seawater. The three different parts are high tide, middle tide, and low tide.

Since the high tide zone is covered in water for a small part of the day, it is exposed to warmer temperatures and drier conditions and thus sees fewer plant and animal species.

However, since low tide parts are covered in water for much of the day, they are more suitable for aquatic life and therefore see far greater biodiversity than the rest of the zone.

The intertidal zone ecosystem is an interconnected web of different animals and plant species that depend on each other for survival, and some species travel up and down the zone for food, or to escape predators this means that none of the zones should be developed on, or disrupted, in order to maintain a healthy ecosystem.

Why are intertidal zone ecosystems under threat?

A range of factors is increasingly putting intertidal zone ecosystems under threat. Climate change-related impacts, from stronger storms through to sea level rise, have the ability to remove habitats and displace animals from their natural habitat.

For example, climate change has started to increase the frequency and strength of storms; intertidal zone ecosystems struggle to withstand these changes. Over the past few decades, tourism in coastal areas has put greater pressure on using beaches for recreation, thus scaring away many animal species, and thereby disrupting the ecosystem.

A recent upsurge in coastal development directly disrupts ecosystems by building on habitats and entire inter-tidal zones. Furthermore, the occurrence of chemical and oil spills has increased as the world becomes more industrialised; these seriously harm intertidal zone ecosystems, often killing many animals. Litter pollution is also a huge problem, with large pieces of plastic, metal cans, and polystyrene harming animals. Protecting and restoring coastal habitats is one of the blue carbon solutions that help cut carbon emissions and support nature.

How does human impact affect intertidal zones?

Intertidal zones, also known as the littoral zone, are unique ecosystems that exist between the land and sea, experiencing regular cycles of exposure and submersion due to the tides. These zones are home to a wide variety of plant and animal species, each adapted to thrive in the challenging conditions presented by this dynamic environment. However, human activities have increasingly exerted pressure on intertidal zones, leading to significant impacts on their delicate balance. In this article, we will explore the various ways in which human activities affect intertidal zones and discuss the importance of conservation efforts to safeguard these fragile habitats.

1. Habitat Destruction and Pollution Human impact on intertidal zones can manifest in the form of habitat destruction and pollution. As coastal populations continue to grow, the demand for land and resources intensifies. This has led to the construction of coastal infrastructure, such as harbors, marinas, and resorts, which often encroach upon intertidal habitats [1]. Moreover, industrial and urban runoff, as well as improper waste disposal, introduce pollutants into these zones, negatively affecting the organisms that rely on them for survival [2].

2. Overharvesting and Collection The intertidal zone provides a rich source of marine life, including various plants and animals. Unfortunately, overharvesting and collection of these organisms for commercial, recreational, or even decorative purposes have become prevalent [3]. Indiscriminate harvesting practices disrupt the natural balance within intertidal communities, affecting population dynamics and, in some cases, pushing species to the brink of extinction. Stricter regulations and sustainable harvesting practices are crucial to mitigate this impact and ensure the long-term viability of intertidal zones.

3. Trampling and Disturbance The increasing accessibility of intertidal zones to the general public has inadvertently led to trampling and disturbance of these fragile habitats [4]. As visitors explore and interact with the intertidal environment, the delicate organisms that call it home can be trampled upon or inadvertently disturbed. This disturbance disrupts feeding and breeding behaviors, as well as the physical structure of the habitat, potentially altering the entire ecosystem's dynamics.

4. Introduction of Non-Native Species Human activities have facilitated the introduction of non-native species into intertidal zones, which can have significant ecological consequences. Ships' ballast water and aquaculture operations, for example, can inadvertently transport non-native species to new areas, where they may outcompete native species for resources and disrupt the natural balance of the ecosystem [5]. These invasive species can cause widespread changes in the intertidal community, leading to cascading effects throughout the food web.

Frequently asked questions

What is an intertidal zone?

The intertidal zone is the area where the ocean meets the land between high and low tides, according to NOAA. It is covered by water at high tide and uncovered at low tide.

What are the zones of the intertidal zone?

NOAA divides the intertidal zone into four zones, from driest to wettest:

Spray zone: damp from sea spray, and underwater only in very high tides or severe storms
High intertidal zone: covered only at the peaks of daily high tides
Middle intertidal zone: covered and exposed twice a day
Low intertidal zone: almost always underwater, except during the lowest spring tides

National Geographic describes three zones (high, middle, and low tide) and notes that the low tide zone has the greatest biodiversity.

What animals and plants live in the intertidal zone?

Rocky shores are home to barnacles, mussels, marine snails, crabs, sea stars, and anemones, along with seaweed and kelp. Sandy shores host clams, sand dollars, and worms, which bury themselves in the sediment to stay cool and moist (National Geographic, NOAA).

Why are intertidal zones important?

They support many living things, including resident and migrating birds that feed there. They also protect shorelines from erosion and keep storm waves away from the buildings along the shore, according to National Geographic. Read more about conserving wetlands and why they matter for a sustainable future.

Protecting these fragile shorelines calls for the same restoration mindset we apply on land — investing in nature before the damage becomes irreversible, not after. Every hectare of forest, wetland, or coastline restored takes pressure off the wider ecosystem, tides included. Find out what blue carbon projects are and how they protect coastal ecosystems. Discover Green Earth's verified carbon solutions and become a sustainability leader by restoring nature where it counts.