What is an Invasive Species?
An invasive species is a plant (or animal) introduced from another region that spreads rapidly and causes problems for native ecosystems.
Characteristics
Rapid Growth
- Fast-growing and competitive
- Outcompete native plants for resources
- Example: Melina in Costa Rica
High Reproduction
- Produce many seeds or sprout easily
- Disperse seeds efficiently
- Establish quickly in disturbed areas
Few Natural Controls
- No natural predators or diseases in new region
- Native herbivores may not eat them
- Allows unchecked population growth
Impact on Ecosystems
Biodiversity Loss
- Outcompete and replace native species
- Create monocultures
- Reduce habitat diversity
Altered Ecosystem Processes
- Change nutrient cycling
- Modify water availability
- Affect fire regimes
Economic Costs
- Damage to agriculture and forestry
- Costly control efforts
- Loss of ecosystem services
Invasive Trees in Costa Rica
Melina (Gmelina arborea)
- Introduced for timber plantations
- Escapes cultivation and invades natural areas
- Spreads along roadsides and forest edges
Sometimes Problematic
- Teak (naturalized but controlled)
- African oil palm (in some regions)
Management
- Prevention: Best strategy - don't introduce
- Early detection: Monitor new introductions
- Rapid response: Remove when populations small
- Control: Mechanical removal, herbicides (careful use)
- Native restoration: Replant with native species
Not All Introduced Species Are Invasive
Many introduced species are beneficial or benign:
- Coffee (doesn't invade natural areas)
- Most fruit trees (stay in cultivation)
- Controlled plantation species
Invasive = Introduced + Spreads aggressively + Causes harm