One of the priority tasks when working to achieve the integrity of natural environments is to know exactly what we want to conserve and/or restore.  To do this, we need to know which species constitute the native vegetation in the area of interest, since they are the base that forms the networks uniting flora and fauna, and will be responsible for maintaining the ecological balance.

A region’s native plants are species that evolved for thousands of years in that area, are adapted to its environmental conditions (climate, soil and natural disturbance regimes) and have co-evolved with other organisms. These plants give identity to each environment, which is how we can recognize jungles, palm groves, woodlands, forests, marshes, grasslands and steppes. Ecosystems are commonly colonized by what are known as exotic species, which don’t belong to them. This phenomenon is not only observed in plants but also in animals, fungi and other organisms. When we speak of exotic vegetation, we are referring to plants moved outside their own natural distribution area accidentally or intentionally by man. Such species that manage to establish themselves in new regions can use resources more efficiently than native vegetation.  Their population size consequently increases abruptly, turning them into invasive species.

What problems can these species generate?

Biological invasions are listed by the International Union for Conservation of Nature (IUCN) as one of the main global threats to biodiversity. Their effects are observed at three levels:

•   Environmental: when they impoverish biodiversity by replacing native species and usurping ecological niches, as well as competing with, displacing, excluding or driving to extinction other plants and animals, thus altering soil chemistry and the water regime, and introducing or enhancing diseases.

  • Social: when they impact our culture and identity. Their abundance makes people believe they are native and part of the original landscape. When this happens, it is usually too late to control them, because it is technically complex, economically costly and culturally “unfriendly.”
  • Economic: when the impoverishment of the natural areas results in the loss of ecosystem services, which are the benefits the environment provides to society. 

To avoid their effects, the first step is prevention.  We must thus be aware of these species and avoid releasing or cultivating them. If this has already happened, their impact must be evaluated and work done to eradicate them from the invaded natural areas. The longer the delay in taking measures to control invasive exotic species, the greater the economic costs due to loss of environmental services, and the higher the costs and time required for eradication.

Identification activity

Next, we will learn how to differentiate two species of trees common in spinal forests, which at first glance are very similar in size, appearance and leaf shape: Tala (Celtis tala – the native species) and Elm (Ulmus pumila – an exotic species). If we are in doubt, we only need look at the underside of the leaves (technically called abaxial side). The Tala has three well-marked veins—one central and two lateral—and “little teeth” on the leaf edge starting half way up and continuing upwards. In addition, this species has small thorns, the characteristic that gave the “Spinal Ecoregion” its name. The elm leaf, in contrast, has many evenly distributed veins throughout the leaf and the entire leaf edge is toothed.  Moreover it has no thorns on its branches.

On the left: Celtis tala, native tree.
On the right: Ulmus pumila, exotic tree.

At the Monte Alegre Nature Reserve, we are actively working to identify and eradicate invasive exotic species in order to continue giving space, light, water and life to the native forest. 

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