Insects: Mini architects of the forests
Felix Francis and Pratha Sah
Insects influence plant growth, climate, and soil conditions. These miniature creatures, which make up half of all known species, have the ability to stabilize their ecosystem over the long term. Consider, for instance, a hypothetical drought: The variety of trees, all fighting for survival, has little water from the dried up soil. If a destructive insect enters this water-hungry forest, it may weaken or kill a certain species. As these insect-damaged trees are weakened, the remaining trees have more water, space, and nutrients to survive the drought.
The idea of insects regulating a system is both a self-serving and cooperative endeavor. By stabilizing some essential key process or structure of the system, the insects ensure the survival of their environment, much like a bee collecting pollen from a flower. Insects are major architects of the plant world in both structure and function, and in natural balance help to maintain healthy and productive forest ecosystems. Insects influence their environments in five key ways:
- Insects aid decomposition, stimulate the breakdown of organic materials, enhance soil fertility and plant growth, burrow in soils and increase its porosity and water holding capacity.
- Insects that eat plants influence where their hosts can grow. Sometimes they kill trees and other plants to reduce competition, and many times feed on trees without killing them in ways that actually improve the health and long term growth of trees and forests.
- Insects are a key food source for other animals, playing a major role in the food chain.
- Insects help disperse seeds, fungal spores, and even other invertebrates from one place to another. Insects are pollinators, and in this role also help control the movement of plant species.
When you have a highly destructive insect epidemic, what you really should be saying is not that we have an insect problem, but that we have a forest health problem. It is monocultures and fire suppression that cause insects to become nuisances. The pests that plague us are all too often a result of our own making. Studies suggest that even when insects eat up to 40 or 50 percent of foliage, they make little or no difference to plant growth and survival. This type of moderate insect damage should not be fought with costly controls, the researchers argue.
Intensive forest management focuses on maximizing wood fiber production and minimizing losses through tree mortality and subsequent decomposition. However, whole communities of insects rely on dead trees for survival, and detritus is a major part of the forest food web. Moreover, without the diversity of a forest to act as a natural barrier, the insects or parasites have little restriction on their growth and dispersal. Several preventative measures exist. Intermixing the species of trees or crops interferes with the insect’s ability to spread from host to host. Before human-management, the structure of the forest that we valued was a reflection of the insects, fires, and pathogens that kept some species out of these forests or restricted them to certain areas of forest.
However, the ways in which our changing forests and forest management practices have affected insect communities and their abilities to carry out these roles are not understood. To effectively manage forest ecosystems, more information is needed on the interactions of land use and forest management practices with arthropods and microbes of forests. As these systems become more fully understood, it should be possible to work with insects, rather than against them, to produce new solutions to maximize the yield of forest commodities while achieving conservation goals and healthier ecosystems.
