Unsustainable development in Areas of Outstanding Natural Beauty (AONBs), now known as National Landscapes, can have several negative impacts in planning terms. AONBs are designated as such due to their exceptional landscapes, and any development in these areas must be carefully planned to protect their natural beauty and environmental quality. Here are some of the negative impacts of unsustainable development in AONBs:

1. **Loss of natural beauty:** Unsustainable development can lead to the degradation of the unique landscapes and natural features that make AONBs special. This can include the loss of important views, the destruction of habitats, and the alteration of natural landforms. Planners must ensure that any development in AONBs enhances or conserves the area's natural beauty.

2. **Impact on biodiversity:** AONBs are often home to a wide variety of plant and animal species, some of which may be rare or endangered. Unsustainable development can result in habitat destruction, fragmentation, and loss of biodiversity. Planners need to consider the potential impacts of development on local wildlife and ecosystems and take steps to mitigate these impacts.

3. **Increased carbon footprint:** Unsustainable development in AONBs can contribute to an increase in carbon emissions and exacerbate climate change. This can occur through the loss of carbon-sequestering habitats like forests or wetlands, or the increased use of energy in new developments. Planners should promote sustainable development practices that reduce carbon emissions and promote energy efficiency.

4. **Pressure on infrastructure:** Unsustainable development can put pressure on existing infrastructure in AONBs, such as roads, utilities, and public services. This can lead to congestion, increased pollution, and strained resources. Planners need to carefully assess the capacity of existing infrastructure to support new development and plan for any needed upgrades or expansions.

5. **Negative impact on local communities:** Unsustainable development can have negative social impacts on local communities in AONBs. This can include increased housing costs, displacement of residents, loss of community character, and disruption of traditional ways of life. Planners should engage with local communities to understand their needs and concerns and ensure that development benefits the community as a whole.

6. **Risk of flooding:** Inappropriate development in AONBs can increase the risk of flooding, especially if natural drainage systems are disrupted or if new developments are located in flood-prone areas. Planners need to carefully consider the potential for flooding in AONBs and incorporate measures to manage and reduce flood risk in their planning decisions.

7. **Loss of cultural heritage:** AONBs often have significant cultural heritage assets, such as historic buildings, archaeological sites, and cultural landscapes. Unsustainable development can result in the loss or degradation of these important heritage assets, diminishing the area's cultural significance. Planners must prioritize the protection and conservation of cultural heritage in AONBs.

8. **Diminished recreational opportunities:** AONBs are popular destinations for outdoor recreation, including hiking, cycling, and nature-watching. Unsustainable development can encroach on recreational areas, disrupt access to public lands, or compromise the quality of the outdoor experience. Planners need to ensure that development in AONBs preserves and enhances recreational opportunities for residents and visitors.

In planning terms, addressing the negative impacts of unsustainable development in AONBs requires a holistic approach that considers the environmental, social, and economic aspects of development. Planners must balance the need for growth and development with the imperative to protect and conserve the natural and cultural heritage of these special landscapes. Sustainable development practices, such as green infrastructure, biodiversity conservation, and community engagement, can help ensure that development in AONBs is compatible with their designation and enhances rather than detracts from their unique qualities.