Revegetation is the method of replanting and rebuilding areas of land cleared of their natural vegetation.
We use revegetation if prior land use has totally removed native plants from the land or when it has extremely disturbed the soil, so we cannot rely on natural regeneration anymore.
It is essential to have proper planning, preparation and monitoring to ensure successful revegetation. All factors — the right technique, purpose, adequate site preparation, and suitable plants — all need consideration.
If not appropriately implemented, revegetation can cost you so much time and money.
How do you know if a revegetation project has been successful? What are the indications of an effective revegetation initiative?
In this article, we have listed six factors that encompass successful revegetation.
1. Diminished Soil Erosion
When human activity disturbs this system, however, erosion rates go higher. Water and wind wear away the nutrient-rich topsoil.
When the soil detaches, moves or deposits into waterways and drains, contaminated farmlands become crippled and environmental threats such as destabilised slopes occur.
Successful revegetation diminishes all these soil erosion problems effectively.
Covering the soil through revegetation protects it from the impact and runoff caused by rain flow. The root system of the plants holds the ground together to avoid its displacement. These roots also prevent destabilisation of slopes and landslides.
Moreover, when strong winds blow through these lands, the roots from trees and plants stabilise the soil and hold it in place.
There should be over 30% of soil cover to reduce erosion risk significantly. Thus, for a revegetation program to be effective, it should fill the land with enough plants.
Additionally, the revegetation project should increase soil infiltration rates and levels of organic matter and improve soil structure. These soil properties reduce soil erosion.
2. Enhanced Biodiversity
The excessive clearing of natural vegetation causes a decline in biodiversity. Revegetation can restore these damaged ecosystems and provide habitat for plants and animals.
Here are some examples of how revegetation enhances biodiversity.
Improved Bird & Wildlife Population
Many scientific studies identify the relationship between revegetating degraded landscapes and improving bird and wildlife population.
Back in 1999, two separate studies by Ryan and Kimber et al. identified the ability of site revegetation to provide habitat for a range of bird species, mostly generalist or edge species.
Revegetation also supported more forest-dependent and declining species than open farmlands.
A study of 12 revegetation sites at four localities recorded a significant number of species and birds present. It also showed that even small scale revegetation projects could create homes for a range of bird species.
Other key findings in papers that related revegetation with bird and wildlife population were:
- Revegetation complexity. Multiple studies have found a positive relationship between the richness of bird species and complex revegetation.
- Revegetation time. Areas that have higher revegetation age had ample time to develop structural diversity and opportunity for colonisation. These attributes help increase the richness of bird species in the area.
- Plant used. Woodland birds are said to have been more diverse when using local plants, while exotic birds were more varied with the use of exotic plants.
- Size of Revegetation.Large and widely revegetated areas had more richness in bird species.
All these findings prove that revegetation, in different conditions, improves the population of wildlife and bird species in the area. Thus, any revegetation project should incorporate a biodiversity enhancement in its design to make it more successful.
Weeds are quite bothersome. They compete with other plants for soil moisture, nutrients, and light. New plants or seedlings have difficulty surviving in the presence of weeds.
Thus, in ensuring a successful revegetation program, one should consider weed control. It should also have up-to-date management and proper intervention.
Once done, it increases seedling survival by 100% and the growth rate by 70%.
So, how do you incorporate an effective weed control program to your revegetation project?
Listed below are the steps that you may do.
- Survey the weed species present in the land to identify actions needed.
- Understand the mechanism of reproduction, density, distribution, invasiveness, and spread of weeds across the site.
- Consider the limits posed by the site, such as difficulty in access, public safety considerations, and proximity to bodies of water that could restrict the use of chemicals and herbicides.
- Conduct a pre-season weed control like pasture topping, close grazing, or cropping a year or two before planting.
- Make sure you do pre-planting weed control methods such as scalping, cultivation, and herbicide application.
- Choose the revegetation method that’s best for the land. Choose also the right species to plant. Some plants can outcompete weeds even after applying initial weed control. Thus, it is sensible to perform weed control activities until the desired plants have the adequate ability to compete against the weeds.
3. Reduced Water Loss and Degradation
Improperly managing the soil can lead to severe land degradation.
Human activities such as overgrazing, improper cultivation, and excessive deforestation degrade the soil. As a result, the ground becomes susceptible to erosion, salinisation, and low productivity.
Furthermore, soil degradation alters properties such as water availability and ability to support root growth. Damaged lands are therefore less able to hold and keep water.
One way to restore degraded lands is through revegetation.
Soane et al. (2012) and Lima et al. (2013) showed that plants could increase water retention and reduce surface runoff speed.
Revegetation is a proven method in decreasing surface evaporation and minimising water loss.
For instance, trees and shrubs can provide shade to the soil — reducing evaporation by 30% and effectively lowering the soil temperature.
Successful revegetation also reduces water loss caused by transpiration. In transpiration, water loss is in the form of water vapour.
When you plant the right species, water lost through transpiration decreases. For instance, some plants have a small surface area or have mechanisms that effectively diminish water loss.
Moreover, it is beneficial to have revegetation plans that properly deal with weeds. Weeds compete with plants for water and increase water loss. Thus, a revegetation project with efficient weed control management also mitigates soil moisture reduction.
4. Cooler Regional Climate
Revegetation also affects the climate significantly, including giving a cooling effect in warm areas.
Plants help improve air quality by taking in and reducing the carbon dioxide present in the atmosphere.
Carbon dioxide in the atmosphere increases at an estimated rate of 3.3 billion tons per year.
Of this rate, 1.6 to 2 billion tons is because of improper land management, changes in land cover, deforestation, and land degradation.
Revegetation mitigates climate change and all these effects by reducing carbon dioxide in the atmosphere and promoting the carbon sequestration ability of ecosystems.
Plants provide a “carbon sink” for the environment.
During photosynthesis, plants absorb carbon dioxide from the atmosphere. In fact, they take in approximately 40% of CO2 emissions in their surroundings. This process significantly reduces the amount of carbon in the atmosphere.
Revegetating previously cleared areas can sequester significant amounts of carbon per hectare.
A study of 264 revegetation sites in South Australia showed an average carbon sequestration rate of 9.5 tonnes of carbon dioxide equivalents per hectare per year.
It is a proven fact that the capacity of plants to sequester carbon increases over their lifetime.
Studies also show that revegetation demonstrated a positive role in the carbon sequestration in the soil by its increasing litter supply and root decay.
5. Increased Soil Fertility
When the soil is fertile, it can sustain plant growth and increase crop yield.
However, many activities can cause a decrease in soil fertility. Some contributing factors are growing crops, leaching, and soil erosion.
Soil erosion removes the nutrients from the soil. Farmlands become unproductive and sometimes barren.
Revegetation can restore essential nutrients in the soil.
One found out out that revegetation promotes a positive relationship between biotic and abiotic factors to accelerate soil development substantially.
On a revegetated site, there is an increase in litter supply and the development of a microbial community. The accumulation of organic matter leads to a lot of positive outcomes, such as the following.
- a decrease in soil bulk density
- increase in soil porosity
- improvement of soil water retention capacity
- growth of soil organisms
Successful revegetation programs efficiently change the properties of the soil and make it even more favourable to plant growth.
Many studies also showed that revegetation successfully improves the fertility of degraded mine lands.
Forest revegetation, on the other hand, can enhance the soil’s organic matter content and nutrients. It can also cause an increase in the cation exchange capacity of the soil.
6. Visual Enhancement
An excellent revegetation project should not just focus on the technical aspects of the land but also the site’s aesthetics.
Choosing the right plant species will give an aesthetically beautiful vegetative cover.
The diverse colours of spring wildflowers can add beauty to the scene. Forbs and shrubs enhance the site’s appearance.
Tall plants improve the visual beauty of the site by blocking views and structures such as borrow, gabion walls and slopes covered by rip-rap.
Planting filler species like flowering forbs can cover unattractive bare spaces in the grass.
Aesthetic considerations also contribute to the time needed to finish a revegetation site.
Wildland or mine sites could take years to rehabilitate. Meanwhile, public areas — where beautification is a priority — would need a faster revegetation plan.
How to Ensure Successful Revegetation
After identifying the factors of a successful revegetation program, it is necessary to proceed to the next step — ensuring success.
How do you make sure the revegetation design will be successful?
What considerations should you take to ensure the revegetation project will yield positive outcomes?
No single revegetation approach will fit all sites. Each area is unique and, thus, needs a specific revegetation program.
To do this, you should first be familiar with the specific conditions of the site to produce tailored solutions. Techniques and applications will then vary depending on the soil conditions, species selection, and revegetation goals.
Below are necessary points that you must secure for every site:
First on the list is surface preparation. This step is necessary to ensure revegetation success.
Prepared sites will give plants the best conditions for germination, survival and growth. Thus, it is never a waste of your time when you invest in the right soil preparation.
Surface preparation involves mechanical or initial soil preparations like clearing of the land, removal of stones and rocks, ripping, mounding, and levelling of the soil. It also includes weed control interventions.
You can use different equipment for different applications. Each depends on the site’s soil conditions, the weeds present in the land, and its location. Site clearing, contour optimisation, and the removal of debris also utilise different techniques.
Determining Land Use
Research and identify the previous usage of the land. For example, you may investigate if there have been previous attempts to revegetate the area.
This information will give you an idea on the soil conditions and other environmental concerns that you will most likely encounter. It will also help you in determining the correct species to use for the revegetation program.
Correctly identifying the plant species appropriate for the specific area you want to revegetate is imperative.
Below is a simple guide on the considerations you can use when you choose plants.
- Revegetation purpose. Determine the purpose of the revegetation project before starting it. This goal will serve as a guide in choosing suitable plants to grow in your area.For example, if your purpose is to bring back a native plant community, planting grasses may not be the best option since they can compete with other plants. However, if you want to control erosion, fast-growing grasses are beneficial.If you want to rehabilitate degraded areas with low soil fertility and structure, choose plants that can create micro-climate conditions and enhance the soil health and moisture.
- Natural habitat.Consider the environment of the site needing revegetation. Then choose plant species that naturally grow or thrive in that area.You can choose plants that can withstand dry soil conditions and put them on slopes. You can also grow plants that can tolerate water in creeks and other wetlands.
- Native and local plants. The ability to adapt to local climate and soil conditions is one attribute of local or native plants. Choose them whenever it is possible, since they are more likely to be self-sustaining.Some plants need more time and care for cultivation. Select only those that suit your schedule for proper maintenance.
Conduct Soil Analysis
Another step to ensure success in revegetation is to determine the soil properties of your site. Through this, you can apply the proper intervention for problematic soils.
For instance, if the soil is too acidic, sulphur or lime may be suitable to mend the soil salinity. You can also add compost to soils with low organic content.
You can enable this by conducting a soil analysis. Do this at least a month before the seeding schedule.
Soil testing can take at least four weeks — from the release of test results up to the time the fertiliser arrives — so you have to make sure you do it ahead of seeding time.
The process of soil testing begins by collecting soil samples from the site. You then send these samples to a laboratory for a comprehensive soil analysis to assess the soil properties like acidity, electrical conductivity and nutrient levels.
The results from the test will assess the seeding rate, the species in the seed mix, and the type and amount of fertiliser to apply.
This soil assessment enables customised solutions for any revegetation project. Thus, it is always best to do soil analysis regardless of the size of the site.
Sowing and Cultivation
When you have selected the right plants, and you have already determined the soil conditions in your area, you are now ready to start the sowing process.
Before you do this step, however, it is crucial to consider a few points to gain the best outcomes for your project.
- Sow when the ground conditions are most favourable.
- Avoid working on a wet ground. Hard clods can form after tillage and grading.
- Choose the right time for sowing.
- Choose the season best suited for your site. If you experience medium to high rainfall, or if your area is prone to frost, plant during spring. If you usually experience hot seasons, it’s best to sow during autumn or winter.
- Do not plant when foul weather is coming. You might not finish the planting process.
- Plant when the ground is moist, and soil temperatures are still starting to increase.
- Apply fertilisers when the ground is dry and complete the process before the rainy season starts.
- Water the plants.
- Proper watering prevents transplant shock and reduces air pockets in the roots for excellent soil contact.
- It is best if you wet the plant’s roots before planting.
- You can use irrigation equipment or simple hand watering when you water your plants. In choosing a method, consider your location, water source, time, and budget.
- Sometimes, it is better to water your plants only occasionally during summer. This will allow the roots to develop more fully.
- Watch out for signs of water stress such as browning or wilting of plants. This will ensure your plants will receive proper treatment.
- Identify the right planting technique for your site.
- You can use direct seeding, natural regeneration, or replanting to establish your vegetation.
- Choose the technique in line with the purpose of your project, the site size and conditions, and your resources.
- Make sure the seeds are fresh and of outstanding quality. Well-grown seedlings are easier to manage.
- Keep the seedlings moist before planting. You might need to make sure they do not dry out because of exposure.
Planting trees is essential when revegetating large-scale landscapes. Trees are beneficial because they provide shelter and habitat for native wildlife and help improve the soil quality.
There are many ways to include plant trees in your site. One method is through direct seeding.
In direct seeding, you sow the seed directly into the ground. Although it could take years to establish trees using this method, they turn out to be stronger with a better root system.
Direct seeding is the most economical method in terms of time, cost, and labour when rehabilitating sizable areas.
Another method for establishing trees is through tubestock or planting of seedlings in small nursery tubes. Compared to direct seeding, tubestock planting is more expensive and laborious. However, because it gives fast and effective results, many revegetation projects prefer this method.
The purpose of revegetation also influences the quantity and density of the trees that need planting.
When rehabilitating forests, trees should compose 20% of the revegetation plan. Scattered timber lots planted randomly are suitable for grazing, especially as shelters for livestock.
You should also space trees according to their height and size. For a more natural effect, plant them alongside creeks or brooks or alternated with shrubs.
Mulching is the application of a protective layer or material, such as straw, to the soil surface. The material guards the ground surface during seed germination or before the application of a permanent cover.
You can use several materials as mulch. A few examples are wood chips, bagasse, hay, sugar cane, leaf litter, compost prunings, and mattings.
Applying mulch to bare soil or exposed sites brings many benefits. Here are some of them:
- Retention of soil moisture.Bare soil quickly loses water as having no cover exposes it to evaporation. It can only absorb a small amount of rainfall because of the higher compression it experiences.Mulches increase soil moisture by reducing evaporation and increasing percolation and retention. A study by Russell (1939) showed that even a layer of straw of 3.8 cm thickness reduced evaporation by 35%.
- Decrease erosion.Bare soils experience increased exposure to wind, water, and traffic-induced erosion. Mulching protects the ground by holding the soil matrix together.Many studies have shown that mulching reduces erosion significantly. Such studies found that straw mulch can lessen soil erosion by as much as 86%. When combined with an erosion net, this reduced erosion by up to 95%.
- Moderate soil temperatures.Too much hot or cold temperatures can kill fine roots or transplants. Mulching can insulate exposed soil from extreme temperatures.
In 1992, Martin et al. showed that organic mulches could lower the soil temperature by 10°C compared to bare soil. They also reduce surface temperatures by evaporative cooling.
Lastly, one of the critical aspects of ensuring success in any revegetation program is monitoring.
Monitoring keeps you in line with how the site progresses and the development of your revegetation project. You can use the information from monitoring to refine and improve your plans and make the necessary adjustments.
Start recording notes of your observations at the beginning of the revegetation project. This will give you the baseline information that you will need to monitor your progress.
Document essential details like the project’s start date, the plants used, and the applied interventions.
Taking photos of the site, regularly, would also prove to be beneficial. Do this for every specified area so that you can identify changes like developing habitats or the effects of climate.
Achieving a Successful Rehabilitation
Success in every line demands a definite aim.
If you want to ensure success in your revegetation program, you must first identify your goals at the start of the project.
From then, do enough preparations and analyses — from the soil conditions to the best kind of plant species for your land — this is to choose the most suitable methods and interventions for your site. Doing this step will help you save time, money, and effort.
Then sow the seeds. Establish your vegetation. If you couple dedication with the techniques and principles written above, success will always be at hand.
Still, while all the above suggestions could prove helpful, remember every site is unique. Thus, it is necessary to understand that every revegetation project needs a committed, tailored solution.
Revegetation of large-scale sites can be tricky. Contact us for a customised solution with proven results.