More than a quarter of the Netherlands lies below sea level, making dunes a crucial defense for coastal communities against the impacts of climate change. As sea levels rise, the safety of Dutch communities depends on understanding and enhancing the strength and resilience of dunes. To help with this, graduate students Paul Berghuis and Floris van Rees from Utrecht University conducted surveys of dunes in August and September from Florida to Massachusetts to better understand how grasses affect dune growth and recovery after storms.
“We have a rich history in the Netherlands when it comes to coastal engineering. Currently, long-term sea level rise is one of the most pressing challenges,” said Berghuis. “There’s a growing interest in nature-based solutions because, unlike rigid structures, natural systems like dunes have the potential to adapt and keep pace with rising sea levels. Our perspective on dunes has been shaped by living in the Netherlands, but being here in the U.S., we’re encountering different ecosystems. It’s both interesting and challenging, and we’ve already learned a great deal.”
Over two months, Berghuis and van Rees conducted surveys of dunes along the Atlantic coast, measuring the layout of plants, grass patches and the shape of dunes to understand how dune grasses contribute to resistant and resilient dunes. They also considered factors like nutrients from nearby bird colonies and climate, which can affect plant distribution. Berghuis and van Rees will compare this data to their research on Dutch dunes.
Dunes in the Netherlands are typically tall and steep, which increases their resistance to storms and hurricanes by preventing waves from overtopping them. There are generally two dune grass species found along its coastal areas, one in the front and one on the crest, and dunes occur in the same climate. In the United States, in contrast, dunes tend to be lower, which provides less protection against storms and hurricanes, and more resilient and able to recover more quickly after storms compared to their Dutch counterparts. They also span a range of climatic zones, are different shapes and their grass species display a variation of shoot configurations. This diversity helps Berghuis and van Rees understand potential correlations between small-scale plant patch configurations and large-scale dune structure, as well as the dynamics of their single-species dunes in the Netherlands more thoroughly.
While earlier studies suggest that plant arrangement and density can influence dune shape and sand buildup, these effects haven’t been thoroughly measured. This study aims to fill that gap and offer new insights into how environmental factors relate to plant traits.
“We also observe distinct shoot configurations between species dominating the northern and southern dunes,” said van Rees. “Literature suggests that the southern species, sea oats, is expanding northward due to warmer winters driven by climate change. Given that shoot configurations significantly influence dune morphology, this shift in species distribution may lead to altered dune shapes where sea oats and marram grass, the northern species, meet. The potential changes along this interface carry important implications for integrated coastal zone management, as understanding and anticipating these morphological shifts will be crucial in adapting to future climate conditions.”
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By Megan Sam