Forests are a critical cog in the water cycle. Termed as the “rivers in the sky”, the trees in the forests act as fountains that suck water out from the ground and releasing it into the atmosphere through the pores of its foliage (Wheeling, 2019). This results in giant “rivers” in the sky whereby clouds carrying heavy water droplets creates rainfall. This cycle is repeated as rainfall falls back into the soil in forest environments, where the tree “fountains” absorb them again. The importance of forests in the water cycle is paramount, and the removal of them risks the drying up of these “aerial rivers” and the lands that depend on them for rain. This will also result in numerous knock-on effects like affecting the agricultural industry that is dependent on rain from the forests (Pearce, 2018).

Whilst deforestation is often identified as the primary contributor to the loss of forests, recent studies have also shown the impact of microplastics on water cycles. It is found that microplastics can change and alter the characteristics of soil, influencing permeability, retention, and evaporation of water (Wan, Xue and Hui, 2019). An experiment was conducted on the effect of plastics of varying sizes on soil desiccation (drying out).

The study concluded that plastics had an accelerating effect on soil desiccation, and a linear relationship was determined between soil evaporation rate and plastic content. The effect was also more pronounced for smaller plastic sizes within the test range. Plastics embedded within the soil allowed the formation of channels that facilitated the transportation of water at a much higher rate, and as a result caused water in soils to be much more susceptible to evaporation (Wan, Xue and Hui, 2019).

This is of particular concern for the water cycle, as plastic pollution in forest soils could significantly reduce the amount of water available. As a result, a massive reduction of evapotranspiration processes will thus lead to less rainfall, which will have knock-on effects on environments and activities heavily reliant on it. Furthermore, with larger plastics facilitating soil desiccation, which forms cracks, the resaturation of soil could also result in the migration of plastics and other pollutants into deep soil layers along the cracks.

References:

Pearce, F. (2018, July 24). Rivers in the Sky: How Deforestation Is Affecting Global Water Cycles. Retrieved October 15, 2020, from https://e360.yale.edu/features/how-deforestation-affecting-global-water-cycles-climate-change

Wan, Y., Wu, C., Xue, Q., & Hui, X. (2019). Effects of plastic contamination on water evaporation and desiccation cracking in soil. The Science of the Total Environment, 654, 576-582. doi:10.1016/j.scitotenv.2018.11.123

Wheeling, K. (2019, October 15). How Forest Structure Influences the Water Cycle. Retrieved October 12, 2020, from https://eos.org/research-spotlights/how-forest-structure-influences-the-water-cycle