How Much Water on Earth is Plant-Available?

Water is one of the most important substances for plants, as it is essential for photosynthesis, nutrient uptake, and growth. But out of all the water on Earth, how much is actually available for plants to use?

The Total Amount of Water on Earth

The total amount of water on Earth is estimated to be around 1.4 billion cubic kilometers (326 million cubic miles). This includes water in the oceans, lakes, rivers, permafrost, and even in the atmosphere. However, most of this water is not available for plants to use.

The Breakdown of Available Water

Out of the total water on Earth, only about 2.5% is freshwater. And out of that 2.5%, about 30% is groundwater, which is water stored beneath the Earth's surface. Another 68.7% is in the form of ice and snow cover in the polar ice caps, mountain glaciers, and other permanent snow cover. This leaves only about 0.3% of the world's freshwater in rivers, lakes, and swamps.

The Importance of Soil Moisture

Of that small fraction of freshwater in rivers, lakes, and swamps, only a portion of it is plant-available. This is because plants can only use water that is held in the soil between particles of soil, known as soil moisture. Soil moisture is the water that fills the spaces between soil particles, which is essential for plant growth because it provides a way for plants to take in the water they need for photosynthesis and other processes.

Soil moisture is affected by several factors, including soil type, weather patterns, and the amount of rainfall. In areas with high rainfall, soil moisture tends to be higher, while in areas with lower rainfall, soil moisture is lower, which can limit plant growth.

The Amount of Water Available for Plants

Scientists estimate that of the world's freshwater, only about 0.003% is plant-available. That may seem like a small amount, but it is still a significant amount when considering the vast number of plant species that exist on Earth, and the essential role they play in supporting life.

It's important to note that the amount of plant-available water can vary greatly depending on the region, the soil type, and the specific plant species. Some plants, such as cacti, are adapted to survive in areas with very little water, while others, such as rice, require large amounts of water to thrive.

The Importance of Water Conservation

Given the limited amount of plant-available water on Earth, it is important to conserve water and use it wisely. This is particularly important in areas that are prone to drought or experiencing a water shortage. Farmers, gardeners, and landscapers can use methods such as drip irrigation and soil moisture sensors to manage water use more efficiently, while individuals can make small changes, such as fixing leaky faucets and taking shorter showers, to reduce water use at home.

By being mindful of how much water we use and how we use it, we can help ensure that there is enough plant-available water for future generations to come.

Conclusion

Water is essential for plant growth, but only a small fraction of the world's freshwater is plant-available. By understanding the factors that affect soil moisture and conserving water, we can help ensure that there is enough water for plants to thrive, while also protecting this precious resource for future generations.