– An extraordinary “earth-engine” shaping and reshaping Guyana’s Coast
Imagine yourself relaxing somewhere along the 280 miles of Guyana’s seawalls. Many of us choose to face inwards, away from the muddy water that, at first glance, seems dirty. But this water holds a fascinating secret, one that has shaped our past, and may now hold the key to a prosperous future on this coast.
This water carries millions of tons of sediment, a vast natural resource of liquid land birthed by the Amazon and transported over thousands of miles to our coastal doorstep. In our previous article, “Through Time and Space: The remarkable forces that shape Guyana’s Rupununi Wetlands,” we traced some of this sediment back to the Rupununi. But this mud speaks of a much bigger story, of colliding continents and giant rivers. A story that begins in the snow-covered peaks of the Andes. The Andes run along western South America, and are the world’s longest mountain range. Formed when two sections of the Earth’s crust collided around 50 million years ago, these mountains are also among the highest in the world (second only to Mount Everest and the Himalayas). Extreme winds, temperatures, and fast-moving water often combine to rapidly erode the Andes, breaking down rocks into fine sediments that are then swept up into small creeks and rivers at the headwaters of the Amazon River.
Almost all of the mud we see on the seawall began its journey like this, high in the Andes. Starting in these creeks, this sediment is transported some 4,000 miles across the continent to the mouth of the Amazon River. In fact, the Amazon River delivers over 1.1 billion tons of suspended sediment and 270 million tons of dissolved organic matter into the Atlantic Ocean every year. This enormous plume of mud, which can be seen from space, kickstarts a giant “earth-engine” that has powered the creation of Guyana’s coast for millions of years.
Known as the “world’s muddiest coast”, the 1,500-kilometre stretch of shoreline between the mouths of the Amazon and Orinoco Rivers hides an underwater landscape that is unlike anything on Earth. As the Amazon plunges into the Atlantic, fresh water and salt water collide with ocean currents, pushing back against the enormous discharge of mud. In this complex mix of tidal forces, the Amazonian sediment is transported back towards the coasts of the Guianas, eventually forming massive mud banks. These mud banks can grow up to 30km wide and 60km long, almost twice the distance between the Kingston seawall and the Cheddi Jagan International Airport.
What’s even more remarkable is that the mud banks then become mobile and begin a slow “walk” from the mouth of the Amazon River towards Guyana. All along the way, as the mud bank passes in front of the shoreline, it slows the high waves coming from the Atlantic Ocean. When slowed, these waves are forced to drop their gifts of sediment and nutrients, leading to the creation of mudflats and sand bars that are exposed at low tide.
Mangroves and other salt-loving vegetation then begin to grow out onto these exposed mudflats, expanding further into the ocean. This is how Guyana’s Low Coastal Plain was formed, and why Guyana’s most fertile soils are found there.
As the giant mudbank out in the ocean continues along its journey west, its buffering effects slowly disappear, and the newly-expanded shoreline once again gets exposed to direct strong waves. This triggers a period of erosion, also called the “inter-bank” phase. Along the coasts of French Guiana and Suriname, this cycle of buildup and erosion continues to result in the gaining of land, where the coasts of both countries have grown over the last few decades.
In Guyana, however, our unique colonial history resulted in the large-scale construction of seawalls and dams directly along the coast, forever changing the behaviour of costal currents, and interrupting this natural earth-engine. Hard coastal structures like concrete seawalls cause wave energy to be deflected, creating more turbulence and much higher wave heights along these human-engineered shores, and ultimately making it difficult for mudflats to form and remain.
With climate change bringing more severe storm surges and higher-than-normal spring tides, Guyana’s coast has never been more vulnerable.
Home to 90% of the Guyanese population and 75% of the country’s agricultural lands, the health and vitality of our entire country depends on the management of our coast, and the mud that made it. This is even more true for our capital Georgetown, which, according to the latest report of the Intergovernmental Panel on Climate Change (IPCC), is at risk of being largely under water by 2030.
The good news, however, is that we can restart the powerful earth-engine that made our coast in the first place; putting Nature to work as we build a resilient future. By combining traditional “grey” sea defences (concrete walls, sea dams, jetties, etc.) with “green”, nature-based approaches (mud, mangroves, saltmarshes, etc.), Guyana can once again gain the advantage in its battle with the sea. We can go beyond simply defending our lands and families from the ocean and begin to expand land into the sea.
We find ourselves at a moment in time when we must build and design with Nature in mind. Taken together, nature-based approaches are among the most affordable, durable and common-sensical solutions to development. As small island states and coastal peoples across the globe fight desperately to stay above the waves, Guyana is in the very enviable position of being able to harness nature to secure our continued prosperity on this coast. Together, we can mount a joint and integrated response, one that matches the sweeping forces and time-scales involved; an approach that brings together State agencies, communities, business interests, scientists and Government; an approach that we will explore in “Generation Restoration: How developing with Nature can shape a better future for Guyanese”, the third and final article in this series.
So, next time you visit the seawall, take some time to look at the mud, for in it lies the stories of our past and the key to our lasting prosperity on this remarkable coast.
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