Benefits and challenges

Step 1: Calculate the total number of organisms ($N$) and $N(N-1)$.

• $N = 12 + 6 + 2 = 20$
• $N(N-1) = 20 \times 19 = 380$

Step 2: Calculate $n(n-1)$ for each species and sum them ($\sum$).

• Oak: $12 \times 11 = 132$
• Ash: $6 \times 5 = 30$
• Birch: $2 \times 1 = 2$
• $\sum{n(n-1)} = 132 + 30 + 2 = 164$

Step 3: Substitute into the formula and solve.

• $D = 1 - \left[ \frac{164}{380} \right]$
• $D = 1 - 0.4315...$
• $D = 0.568$

(Note: A value closer to 1 indicates higher biodiversity).

Challenges to Maintaining Biodiversity

If biodiversity is so crucial, why is it declining rapidly? The main issue is a constant conflict over land use. A growing human population requires space for housing, agriculture, and infrastructure, which inevitably destroys wild habitats.

This destruction causes habitat fragmentation, where continuous forests or meadows are carved into small, isolated patches. This introduces edge effects; the borders of these fragments experience harsher wind and light conditions, which kill off sensitive interior species. Furthermore, infrastructure like roads creates barrier effects that split populations, leading to genetic isolation and a shrinking gene pool.

Conservation is also financially demanding. Running monitoring schemes requires significant government funding, which competes with other social needs like healthcare. Additionally, rapid climate change is shifting temperature zones faster than many species can migrate, leading to local extinctions regardless of how well a specific habitat is protected.

Conservation Agreements and Enforcement

Protecting wildlife requires action at both a global and a local scale. CITES is an international agreement between over 180 countries designed to prevent extinction caused by the wildlife trade. Species on Appendix I (like tigers) face a total ban on commercial trade, while Appendix II species are strictly controlled via permits.

Enforcing international agreements is incredibly difficult, but modern technology helps. DNA profiling is used forensically to trace seized ivory back to specific regional populations, while remote sensing via satellites detects illegal logging roads in the Amazon. Some keystone species are even fitted with GPS collars to create geofencing alerts, which notify rangers if an animal wanders into a high-risk poaching zone.

At a local level, the UK uses SSSI (Site of Special Scientific Interest) designations to provide in situ conservation. These legally protect specific habitats from development and pollution. However, SSSIs cause intense social conflict; they can drop land values by up to 50% and impose strict agricultural restrictions (called OLDs - Operations Likely to Damage), severely limiting a farmer's income. When local habitats cannot be saved, scientists rely on ex situ conservation, such as seed banks and zoo breeding programmes.

Environmental Monitoring

Nature often shows signs of pollution long before scientists bring out their testing kits. Indicator species are organisms whose presence or absence reveals the health of an environment.

Lichens are excellent air quality indicators because they absorb water and nutrients directly from the air. Sulfur dioxide ($SO_2$) from burning fossil fuels dissolves in rain to kill sensitive species. Clean air supports bushy and leafy lichens (and blackspot fungus on roses), but highly polluted air leaves only crusty lichens or a complete "lichen desert".

Water quality is monitored by observing aquatic invertebrates, which vary in their tolerance to dissolved oxygen. Clean, highly oxygenated water supports stonefly larvae and mayfly nymphs. In contrast, if raw sewage enters a river, it causes eutrophication, depleting the oxygen. This leaves only pollution-tolerant species like bloodworms and sludge worms.

Comparing Biological and Chemical Monitoring

While indicator species are useful, ecologists often combine them with chemical monitoring using oxygen probes, pH meters, and nitrate tests.

Worked Example: Estimating Populations from Kick Sampling

A student conducts kick sampling in a stream to monitor water quality. They use a net with a sampling area of $0.2\text{ m}^2$ and catch 15 mayfly nymphs. Calculate the estimated population density per square metre.

Step 1: Identify the sample area and the number of organisms caught.

• Sample area = $0.2\text{ m}^2$
• Organisms caught = 15

Step 2: Scale the sampled area up to $1\text{ m}^2$ by dividing the count by the area.

• $\text{Estimated Population} = 15 \div 0.2$

Step 3: State the final answer with units.

• $\text{Estimated Population} = 75\text{ nymphs/m}^2$

Ecotourism and Sustainable Development

Can flying thousands of miles to look at animals actually help save them? Ecotourism is a form of travel aimed at supporting conservation efforts and local communities. It promotes environmental stewardship and sustainable development by ensuring natural resources are preserved for future generations.

Ecotourism provides a powerful economic incentive: live wildlife becomes more valuable than dead trophy animals. Successful projects channel up to 95% of revenue back into the local community. To prevent habitat damage, managers establish a strict carrying capacity (the maximum number of visitors an area can sustain) and build low-impact infrastructure, such as elevated walkways to prevent trampling.

However, ecotourism has major drawbacks. Constant human presence causes severe disturbance, which can disrupt hunting patterns and lower reproduction rates. Furthermore, building lodges and roads inevitably causes some habitat loss. Finally, the industry suffers from "greenwashing", where profitable tourist activities falsely claim to be eco-friendly despite damaging the environment.