Mounds Increase Diversity

tall large termite mounds protrude from the ground on a sunny day in australia

Biological Strategy

Mound-building termites

AskNature Team

Image: Herbert Bieser / Pixabay / Free non-commercial use

Manage Disturbance in a Community

When environmental conditions change, they can disrupt an ecosystem’s equilibrium. Excessive rain can cause flooding and drought can cause forest fires. An ecosystem must be resilient to such disturbances. Disturbances are unpredictable in location, size, and intensity, so ecosystems must be able to regrow and must have a variety of duplicate forms, processes, or systems that are dispersed in location. For example, a forest ecosystem can recover from fire because diverse organisms play different roles in different ways and in different locations. Many organisms can resprout or grow from seeds triggered by fire, and their dispersed distribution ensures that an entire population isn’t decimated. Though the recovered ecosystem may look totally different from the pre-fire one, the ecosystem as a whole remains healthy.

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Control Erosion and Sediment

Ecosystems must maintain their soils on site and prevent it from being washed away. Organic matter, minerals, and other nutrients in soil support organisms from microorganisms to the largest mammals. But because of the pull of gravity, water flows unless impeded. Therefore, the presence and actions of many, diverse organisms hold soils in place and slow water to allow sediments to settle out rather than be washed downhill. For example, in forests, downed logs that fall crossways to the slope efficiently slow water flow, trapping soils carried by the water and causing water to soak into the soil. In areas lacking logs and other structures, water can flow so fast that it cuts into the soil, causing erosion that washes the soil away.

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Cycle Nutrients

In ecosystems, there is no such thing as waste. Instead, one organism’s waste can be considered as another organism’s resource, and the cycling of nutrients may be the most important form of recycling in living systems. But sometimes those nutrients are transformed by one organism into a form that isn’t readily used by other organisms. For example, lignin is a complex organic molecule found in the cell walls of plants. In a forest, it’s one of the hardest molecules to break down in woody vegetation. Therefore, ecosystems include organisms that are particularly well-adapted to break down different types of nutrients. In the case of lignin, some fungi and bacteria release lignin-modifying enzymes that can break down the lignin to form carbohydrates and other life-supporting chemicals.

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Maintain Biodiversity

The greater the amount of genetic and species variation in an ecosystem, the more resilient that ecosystem is to disturbances. Variation in ecosystems across the Earth also contributes to the Earth’s resilience to unpredictable changes. This variation is called biodiversity. Because living systems compete with each other for scarce resources, maintaining biodiversity involves creating conditions for a large variety of species to successfully co-occur and reproduce. For example, within a wetland, there are different vegetation types. This diversity results in a complex mosaic of microenvironments as the vegetation types alter air flows, light regimes, and water temperatures and chemistry. Because organisms vary in their ideal environmental conditions, these micro-environments increase the diversity of plants in the wetland. In turn, having a wetland in an otherwise dry area increases biodiversity at an even larger scale.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The mounds created by some termites increase diversity in wetlands because they form 'islands,' supporting trees and other species during the wet season.

“On the Okavango, the point of formation of many tree islands is a termite mound. Colonies of the mound-building termite (Macrotermes michaelseni) build subterranean nests during prolonged dry periods in seasonally flooded areas (Fig. 5.13). These nests are eventually crowned by a turret connected to the nest by a series of air passages. These turrets or mounds can be 4 m tall and have a basal area of 50 m² (Dangerfield et al. 1998). Termite colonies redistribute resources by moving fine soil particles to their nests to build up the mound, thus changing the local topography and soil textural properties of the wetland. Termites also carry organic matter to their nests, thus redistributing nutrients locally. Because of their elevation above the floodplain, termite mounds can be colonized by tree species. During the wet season, the termite colonies may be killed. However, any trees on the mounds survive because they are growing above the mean water level. The presence of trees attracts birds and other animals that carry seeds and nutrients to the newly formed island (Fig. 5.13). Consequently, tree islands become hotspots that are colonized or used by a variety of plant and animal species.” (van der Valk 2006:104)

“Many organisms create or alter resource flows that affect the
composition and spatial arrangement of current and future organismal
diversity. The phenomenon called ecosystem engineering is considered
with a case study of the mound building termite Macrotermes michaelseni.
It is argued that this species acts as an ecosystem engineer across a
range of spatial scales, from alteration of local infiltration rates to
the creation of landscape mosaics, and that its impacts accrue because
of the initiation of biophysical processes that often include feedback
mechanisms. These changes to resource flows are likely to persist for
long periods and constrain the biological structure of the habitat. The
value of ecosystem engineering is discussed as a holistic way of
understanding the complexity of tropical ecology.” (Dangerfield et al.
1998:507)