The seed island method is based on the way that plants establish and spread naturally and seeks to work with, and accelerate, natural processes. Rather than trying to restore whole hillsides at once, restoration efforts are focused on carefully selected microsites which have been identified during initial site surveys.
These sites have been identified as being the most favorable to facilitate the germination and survival of the subject species due to aspect, slope, moisture availability, shelter, soil depth etc. Suitable species-specific sites might include moist depressions, sheltered and frost-free spots, sunnier locations, or more shaded spots depending on the species to be sown. Sites that are exposed to prevailing winds or those which are overly wet and waterlogged may be unsuitable for the establishment of some native tree species.
Microsites may also be chosen because they are safer and easier to access, because there is less ground cover of pine needles / leaves and other debris, or because there is a lower risk of weed invasion. Consideration should also be given to how these microsites will be fenced to exclude animals, how easily fencing materials can be brought to the site, and how easy it will be to revisit the site to undertake maintenance and monitoring. Ease of access and safety must be maintained at all times.
Seed is then broadcast into the microsites only. Continued management of emerging seedlings will be required but this is far easier to do with islands of seedlings rather than trying to manage seedlings spread sparsely across a whole site. For example, it may be cheaper and easier to provide temporary fencing to keep animals out of the individual islands rather than fencing the whole site, plus it’s cheaper and easier to manage competition from weeds at a localised level.
The aim is to establish islands of mixed native species across the site, rather than trying to restore the whole site at once. Trees will eventually form a closed canopy under which new seedlings can emerge, and the canopy will grow outwards allowing new seedlings to grow at the fringes of the island.
Fruit-eating birds will be more attracted to these islands rather than single trees. Birds help to distribute seeds from one island to the next and will help to create new islands in between. Pollination by invertebrates will also be facilitated. Eventually, the islands will expand towards each other and merge. This can be facilitated by sowing new islands each year as more seed becomes locally available.
The environment under the canopy creates a much more suitable habitat for many native plants by providing protection against water stress, sun scorch, frost and winds. Canopy cover can also allow for successional species to establish if seed is present. With any restoration project it is, therefore, important to achieve canopy cover as quickly as possible. This is more realistic through the creation of islands rather than spreading restoration efforts too thinly across the whole site.
It is, however, important to be aware of edge effects. Larger seed islands have a more stable micro-climate in the centre with consistent light levels and the closer to the edge you get, the more light / wind / exposure increases. Some species such as mānuka may favour the edge due to increased light levels, but edges also have pressure from exotic weeds and are subject to more extreme climatic conditions. For these reasons, it may be preferably to have fewer, larger islands rather than many smaller ones.
An example of where the seed island approach has been particularly successful is the work undertaken by the Salmonds at Waikereru Ecosanctuary.
The seed island method has the added advantage of managing another key success factor for restoration projects, and that is people’s expectations. Natural native forest restoration may take decades and may even span across generations, however, there are growing expectations that restoration objectives should be achieved much more quickly than this. This may be due to a combination of funding timeframes (usually 3 years maximum), election cycles and the ever-growing human cultural traits of impatience and the need for instant gratification. The human pace of life may have sped up, but native species have not evolved at the same pace.
Restoration projects which involve planting nursery-raised seedlings can provide instant gratification when the seedlings are planted in the ground, but seed-based restoration projects require a lot more patience. It is vitally important that the expectations of funders, landowners, volunteers, peer groups, employees and stakeholders are managed effectively. If positive results are not achieved within the first 1 - 2 years, then the interest and support of those needed to drive the project may begin to wane.
By focusing restoration efforts on islands rather than diluting efforts across the whole site, localised success is far more likely, which helps to keep everyone involved engaged. It’s more rewarding to take people to an island where a blanket of emerging seedlings can be seen, rather than scouring the whole site for the occasional seedling emerging here and there.
Securing more funding is also more likely for projects where success is proven rather than projects where it’s hard to demonstrate any success. By keeping people engaged, more seed islands can be added in subsequent years when seed becomes locally available, therefore accelerating and maintaining momentum of the restoration project.