Ecosystems and conservation

Cacti and succulents in ecosystems

Plants play a vital part in ecosystems. They are “producers”, capturing light energy from the sun and using the chemical reactions of photosynthesis to create sugars (carbohydrates). The plants are then eaten by animals, creating the bottom of a food web. Without plants, the rest of the ecosystem would collapse.

Cacti and succulents are specialised to live in areas that are arid – so they are often an extremely important part of the ecosystem in these areas where most plants would struggle to survive.

Food

All cacti and succulents reproduce with the help of an animal pollinator, whether this is an insect, bird, or even a mammal. There needs to be a reason for the pollinator to visit. Flowers offer sugary nectar and protein-rich pollen as food for the pollinator. Many pollinators depend on specific plants for their food.

For example, the lesser long-nosed bat (Leptonycteris yerbabuenae), lives mainly on the flowers of Agave. If either the plant or the bat were to go extinct, the other would disappear as well.

Pollinators often become food themselves for predatory animals higher up the food chain, like insectivorous birds or birds of prey.

A pollinated flower will swell and develop into a fruit. By surrounding their seeds in sweet flesh, the plant attracts other animals to snack on the fruit and spread the seed in their dung.

Tortoises are particularly fond of cacti and their fruit. As the cacti store water, they are one of the main sources of hydration for the tortoise, as well as nutrition.

Shelter

Plants also provide a home for many animals, and sometimes other plants – cacti and succulents are no different.

For example, North American mourning doves (Zenaida macroura) particularly like to build nests in the branches of Opuntia cacti. The vicious spines of the plants keep most predatory animals away.

Gila woodpeckers (Melanerpes uropygialis) actually carve into the bodies of saguaro (Carnegiea gigantea). Amazingly, the cacti are not harmed, as their transport systems are found right in the middle of the plant. The woodpecker bores into the water-storing areas of the cactus which soon dry over.

Human development

Human development is one of the main factors in habitat loss for cacti and succulents. One example comes from the Moctezuma River valley in Mexico. The mountainside slopes of the valley were, until recently, the main habitat for the golden barrel cactus (Kroenleinia grusonii). This is one of the most common cacti grown by people for decoration: you may have seen one at shops selling houseplants.

In the early 1990s, the Zimapán hydroelectric dam was built across the river, and in 1994 a large reservoir flooded the valley. In this single event, most of the cactus’ habitat was submerged. You can see how the valley looked before and after the reservoir filled up in the image below.

Thankfully, another wild population of this cactus has since been discovered, but the golden barrel cactus is still considered Endangered (in the wild) because its numbers have decreased so drastically. Other threats to cacti through human development include:

• Construction of roads
• Housing and commercial developments
• Mining and quarrying
• Farming