Understanding Ecological Compensation: Can Introduced Species Really Fill the Gaps?

Mitigation is the preference, followed by specifically measurable offsetting, with compensation as the last resort. This order is called the mitigation hierarchy. There are many practices used within this hierarchy. These include: 

• avoiding and minimising loss from the start of the project 
• undertaking management measures, such as pest management and restoration of the degraded area
• performing on-site rehabilitation 
• restorative planting to mitigate habitat loss 
• habitat creation and protection
• pest control to prevent further loss to biodiversity 
• ongoing monitoring of the affected areas, particularly to ensure the efficacy of the measures taken

Focus on Functionality

The heart of this approach lies in increasing the resilience of the ecosystem. In other words, its ability to resist and bounce back after an interruption to its regular ecological activity. By aiming to restore processes and maintain function within the ecosystem, we set them up for future success. 

One of the key components to this resilience is biodiversity. Studies have found that increased genetic diversity leads to increased ability to withstand and adapt to unpredictabilities. 

The Role of Pest Control 

One of the methods used across all three stages of the mitigation hierarchy is pest control. Pests are a common problem as they destroy native species and often have few or no natural predators. It is especially important to take steps to reduce pest activity when the ecosystem is taking damage from human activities. 

Pest control was one of the primary methods used by Waka Kotahi/NZTA in their work to balance out the environmental impacts of the Mount Messenger Bypass in Taranaki. Alongside the replanting and restoration, they implemented extensive pest management over an area of 560 hectares. 

This strategy targeted several species of pests including rodents, goats, feral pigs, and possums, but it is not over. There is an ongoing commitment to control the pest population to very low density. This will continue until this kind of management is no longer necessary to maintain the levels of biodiversity that were created. 

The Role of Introduced Species in Biodiversity

In the conversation around ecological compensation and biodiversity, there has been a focus on eradicating invasive species to allow the native ones to flourish. In recent years, the beneficial role of some introduced species within ecosystems has started to be talked about.

There is a difference between introduced species and invasive species: 

• An introduced species is any species whose presence in an area is due to human interaction – whether intentional or accidental. 

• An invasive species is an introduced or non-native species that overtakes and is detrimental to native species. 

Some introduced species become invasive, turning widespread and negatively impacting the existing ecosystem. However, some studies show that controlled introduction can lead to increased biodiversity and even encourage native species to thrive by: 

• providing or helping to maintain existing habitats
• increasing population of native species due to increased pollination
• aiding in seedling development and establishment

One local example is European gorse, which has helped stabilise coastal slopes in New Zealand, while also acting as a nursery for native plants. 

However, the introduction of new species does require careful monitoring. There is always a risk of this going wrong. That species may become invasive, taking over the area rather than working harmoniously to encourage growth. 

For example, the cane toad in Australia was introduced with the specific goal of pest control, but quickly spread throughout large portions of the country. This caused severe environmental impacts. The cane toad was a quick breeding species which carried non-native diseases and poisoned the numerous native species that prey on it. They are still a problem today. 

Environmental Restoration at Home

While the main focus of ecological compensation is maintaining – if not improving – the indigenous biodiversity within an area in response to the impact of human development, the goal at the very core of it is a functional, resilient ecosystem. However, environmental restoration is a group effort. 

There are many things we can do to help with environmental restoration in our own neighbourhoods, including:

• assisting with local pest control efforts 
• planting native trees and plants on our properties 
• keeping our pets on leashes, or well-contained at home for roaming pets such as cats who are predators to many of our native bird species

Join a community of conscientious kiwis working to help protect our native ecosystems from their own homes. Every little bit counts!