In a previous post, I talked about how climate change is a major threat to the coastal ecosystems of the world. But I also said that that’s not the only threat….
Truth is, most of the effects of climate change can be buffered by the ecosystem itself. That’s because climate change is not a new phenomenon. Ecosystems of the past have learnt to deal with it and have even survived it. The real reason why the current climate change poses a threat is that it is coupled with something that has never happened before in geological past: human effect.
Humans possibly pose a bigger threat to the coastal ecosystems than climate change, because our intervention is more direct, more rigorous and more continuous…
In this post, I will specifically look at the effect of human habitation on coastal ecosystems.
Living on the coasts…
1/3 of the world population lives on the coasts, with 40% living within 100 km of the coast. The presence of human settlements itself, is an alteration to the coastal ecosystem. We have a tendency to build buildings, extract groundwater, drain natural lagoons and wetlands and break the natural flow of winds. All of this has a significant impact on coastal chemistry and physical processes.
Wetlands and lagoons…
Our buildings in these areas cut off the connection between the ocean and the inland waters. This generally causes inland lagoons and wetlands to become starved of water and eventually dry off. Along with that, the organisms living in these small ecosystems die.
But more often than not, humans deliberately drain lagoons and wetlands (unless they serve other economic purposes) to free more land for human settlements. They areas are filled with the sand taken from the beaches, leveled and made suitable for construction. It is not just lagoons and wetlands; salt marshes, tidal flats, swamps and creeks are also sometimes not spared. Massive biodiversity is lost because of all this.
In tropical and sub-tropical areas, esturian and mangrove habitats are dredged to create land for habitation. These environments are important nurseries for many fish species. The dredging and infilling puts many of these fish species at the risk of extinction, because they now have no suitable place to spawn. Further, the loss of plant life in these environments increases the erosion rates in coasts. Consequently, more sediment is transported to the sea, which adversely affects the habitats underwater.
The threat of natural disasters…
The biggest threat to humans living so close to the coast is through natural hazards. Cyclones (or hurricanes), storm surges and tsunamis cause huge devastation every year to these ares. Normally, the coastal ecosystem has ways to buffer most of the impact of these natural phenomena. They are geomorphically equipped with this ability. The lagoons and wetlands tend to act as a sink for excess water. High rise waves are stopped from entering too far inland by the beach berms. If the berms are breached, coastal dunes act as the second line of defense. Tidal flats are large areas specifically meant to hold excess water. Many channels exist that quickly drain excess waters back into the ocean after such events.
But when humans start living in the coasts, most of the geomorphic features of the beaches are destroyed. You wouldn’t see berms and dunes. You wouldn’t see as many streams. The result? Huge loss of life and property.
Groundwater extraction in coasts present another interesting situation. This is how aquifers are placed in the coasts….
So, the more freshwater is extracted, the more saltwater enters into the aquifer region. This makes the underground areas of the coast more and more saline. In most regions, the danger of salt water intrusion is greater than salt water inundation through sea level rise. More salt water in the aquifers will make the area very harsh for plants living in the area. They already face tremendous stress from the saline environment. They could, of course, adapt to the increased salinity, but the adaptation is very slow compared to the rate of change of salinity.
Moreover, humans living in the coasts are now facing acute water shortage preciously because of the over-extraction of groundwater.
What do the people living there do for sewage and garbage? Dump them in the oceans, of course! This remains the greatest problem of human habitation in coastal environments. Wastes discharged into the water creates toxic conditions for the organisms living there. The ocean chemistry is also massively altered. Many of these garbage particles are non-biodegradable and get transported elsewhere by ocean currents.
Today, many regulations are present to control the waste discharge. However, this is one part of the world where waste treatment and recycling plants are absolutely essential.
In all, just the mere presence of humans in coasts, along with the basic activities they undertake to make a comfortable life, are enough to massively alter coastal ecosystems. What of our economic activities in these areas? Stay tuned for the next post.