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Indicator Plants

Updated: Apr 5, 2023

Everything is connected in nature. Each organism contributes to and depends upon its ecosystem to grow and thrive. Some species are tolerant and can thrive in many conditions, while others are a bit more picky. Knowing the conditions that satisfy the niche of a species can reveal clues about the environment you find the organism in. These types of organisms are called indicator species. So what do indicator plants reveal about their environment? Let's get into it!

Starting in our own backyards, the plants in our lawns can be indicators of the amount of activity taking place on it. Grass does not like to be stepped on. It can tolerate it from time to time but repeated foot traffic will cause grass to die. This gap in the environment is then filled by opportunistic species like broadleaf plantain and dandelion, the plants some consider to be weeds. Weeds are very persistent because of how tolerant they are of many ecological conditions. So next time you're in the backyard, or at the park, take a look at the grass and see if you can find areas with a higher concentration of weeds compared to grass. This can reveal the regular paths of animals, or areas with constant human activity.

The next organism is actually only half plant. Lichens are a symbiosis of algae and fungi that work together to survive. The fungi help with mineral absorption from the environment and provide a suitable substrate for the algae to grow on and who then provide energy through photosynthesis. Together they can grow on the sides of trees and rocks and other stationary objects in forests. Lichens are sensitive to the amount of nitrogen in the air making them indicators of the air quality. Forests filled with lichens show that the air quality in that ecosystem is clean. If the lichen population starts to decline, that can indicate a shift in the amount of nitrogen in the air. A common contributor of atmospheric nitrogen is the burning of fossil fuels.

Even the trees reveal that which is unseen. Some species thrive better in dry, chalky soil like beeches, while others tolerate wet soil closer to bodies of water including the sycamore, and willow trees. But willows are not tolerant of sulfur dioxide, making their presence an indicator of clean air that's not polluted by burning coal or other factory emissions. And sycamores require fertile ground, so their presence reveals the quality of the soil. The soil can even be acidic, which is revealed from the presence of white pine and oak trees, which do well in acidic conditions. While some species like the norway maple prefer alkaline conditions

All plants need water, but some rely on it more than others. Cattails are easily recognizable water loving plants that have tightly packed seeds in a cylindrical bundle on the top of a tall stalk. Cattails thrive well in slow moving water like the sides of ponds where their seeds can take root in the mud. These plants are called nature’s grocery store by some foragers because of its many usable parts. The roots and inner stem provide carbohydrates, the pollen provides protein, the leaves provide a waterproofing base for tents, and their seeds can provide cushions and thermal insulation for clothing. But what makes this plant an indicator species is that because of their tall stalks, they can reveal the location of slow moving water that may not be visible. Sometimes it's obvious that the cattails are next to water like a large pond, but sometimes small clusters can reveal little unseen pools of water. For example on the side of the road or on the side of highways.

Every species has specific conditions that it can grow in. Knowing what conditions a specific organism thrives in will reveal a lot about the environment around it. Those pesky weeds many people don’t like can reveal the hidden pathways of animals, a delicate symbiosis of algae and fungi can tell you how clear the air is that you’re breathing, the trees can tell you about the ground you’re standing on and cattails can act as signal flags to reveal the presence of water. Using these species as indicator species will help you feel more connected to the environment , its health, and your health as well.


“The Lost Art of Reading Nature’s Signs” - Tristan Gooley

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