What is Biodiversity?
Biodiversity means "the variety of life" - all the different kinds of plants, animals, fungi, and microorganisms living together in a place. It includes not just how many species exist, but also their genetic variety and the different ecosystems they create.
Three Levels of Biodiversity
1. Genetic Diversity
Within a single species:
- Different genes in population
- Variation in traits
- Adaptation potential
- Disease resistance
Example: All Guanacaste trees are one species, but individuals vary in:
- Leaf size and shape
- Flowering time
- Drought tolerance
- Growth rate
2. Species Diversity
Different species in a community:
- Number of species (richness)
- Relative abundance (evenness)
- Functional roles
- Trophic levels
Example: Costa Rican rainforest might have:
- 100+ tree species per hectare
- Thousands of insect species
- Hundreds of bird species
- Complex food webs
3. Ecosystem Diversity
Different habitats in a landscape:
- Rainforest, cloud forest, dry forest
- Rivers, wetlands, mangroves
- Mountains, valleys, coasts
- Different successional stages
Why Biodiversity Matters
Ecosystem Services
Provisioning:
- Food, medicine, timber
- Fresh water
- Genetic resources
Regulating:
- Climate regulation
- Flood control
- Disease control
- Pollination
Supporting:
- Soil formation
- Nutrient cycling
- Primary production
Cultural:
- Recreation
- Education
- Spiritual values
- Aesthetic beauty
Costa Rica: A Biodiversity Hotspot
Remarkable Statistics
- 0.03% of Earth's surface
- 5% of world's biodiversity
- 500,000+ species estimated
- 25% land protected
Why So Diverse?
Geographic factors:
- Bridge between continents
- Pacific and Caribbean coasts
- Mountain ranges (0-3800m elevation)
- 12+ life zones
Climate factors:
- Tropical location
- Year-round warmth
- Varied rainfall patterns
- Seasonal transitions
Measuring Biodiversity
Species Richness
Simply counting species:
- Most basic measure
- Easy to understand
- Doesn't account for abundance
Shannon Index
Accounts for both richness and evenness:
- Higher value = more diverse
- Considers rare and common species
- Used in scientific studies
Functional Diversity
Different roles species play:
- Nitrogen fixers (legumes)
- Pollinators (hummingbirds, bees)
- Seed dispersers (bats, birds)
- Decomposers (fungi, bacteria)
Threats to Biodiversity
Major Causes of Loss
- Habitat destruction: Deforestation, agriculture
- Climate change: Altered rainfall, temperatures
- Pollution: Pesticides, plastics, chemicals
- Invasive species: Outcompete natives
- Overexploitation: Hunting, logging, collection
In Costa Rica
Historical loss:
- 1940s: 75% forest cover
- 1987: 21% forest cover (minimum)
- 2020: 54% forest cover (recovering!)
Success factors:
- Payment for Ecosystem Services (PES)
- National park system
- Ecotourism economy
- Reforestation programs
Tree Biodiversity
Why Trees Are Key
Forest structure creators:
- Canopy provides habitat
- Roots stabilize soil
- Trunks create vertical habitat
- Dead wood feeds decomposers
Support networks:
- One tree species supports hundreds of insects
- Insects feed birds and bats
- Fruits feed mammals
- Flowers feed pollinators
Costa Rican Tree Diversity
Approximately 3,000+ tree species:
- More than all of North America
- Concentrated in small country
- Many endemic (found nowhere else)
- Wide variety of families
Conservation Strategies
Protected Areas
National Parks:
- 27 national parks
- Protect representative ecosystems
- Tourism revenue funds conservation
Biological Corridors:
- Connect isolated fragments
- Allow animal movement
- Genetic exchange between populations
Sustainable Use
Agroforestry:
- Trees + crops
- Maintains some biodiversity
- Shade-grown coffee, cacao
Selective logging:
- Less impact than clear-cutting
- Allows forest regeneration
- Provides income
How Trees Increase Biodiversity
Single tree supports:
- Epiphytes (orchids, bromeliads)
- Lichens and mosses
- Nesting birds
- Fruit-eating mammals
- Pollinating insects
- Decomposer communities
Example: One Guanacaste tree can host:
- 50+ epiphyte species
- 100+ insect species
- 20+ bird species
- Multiple mammal species
Why It Matters
Understanding biodiversity helps with:
- Conservation priorities: Protect biodiversity hotspots
- Ecosystem management: Maintain functional diversity
- Restoration: Choose diverse native species
- Climate resilience: Diverse ecosystems adapt better
- Human wellbeing: Biodiversity provides services we depend on
Field Recognition
Signs of high biodiversity:
- Many different tree species
- Varied canopy structure
- Abundant epiphytes
- Diverse bird calls
- Healthy understory
- Evidence of wildlife
- Complex forest structure
Take Action
Support biodiversity:
- Plant native tree species
- Avoid invasive plants
- Support local conservation
- Choose sustainable products
- Visit and fund protected areas
- Reduce, reuse, recycle
- Learn and share knowledge