Saturday, 3 May 2014

Some thoughts on the rehabilitation of sugar cane land into natural like grassland in the coastal regions of northern KwaZulu-Natal

A brief overview
In my professional opinion I believe it is an illusion to believe that in the short term one can recreate natural like grassland on a large scale. I believe that the best and most cost effective method is to set the process into motion, to guide it, to manage it and to keep it free of invasive aliens as best as can be done. Clearly the more the money that is invested into the project the quicker the results will be, but the higher cost can never be justifed.

Aloe maculata and berkheya spiciosa growing in my grassland at Mount Moreland

Unless one works in a cost effective manner together with nature in today’s economic climate it is going to be impossible to justify the expense of re-habilitation.  

If I was set with the task of re-habilitation of a large tract of sugar cane land into natural like grassland I would set about the task using the system and methods described in the rest of this brief article.

In my opinion there are many approaches that would deliver acceptable results and that there is no absolute right or wrong. We do not know for sure what was there before sugar cane but can give it a guess based on experience, local knowledge and looking at sites in surrounding areas with untouched or minimally damaged grassland. There could very clearly be elaborate and colorful designs put forward by office experts where nature will not comply with the designers wishes. Designs that would dazzle but that could never be implemented no matter how much money one invests into them. When dealing with nature there are certainly no guarantees that any expert can give. Regardless of our skills or lack of skills nature will have the last say the sooner we realize this the more successful we will be and the more money we can save arriving at an acceptable result.

As a case study I propose the re-habilitation of portions of sugar cane lands at the new Durban King Shaka International Airport as I know this area well having flown many hours low over the leveled areas since work was started on the site in about April 1971. I also often landed on the site long before the present airport was built. I now live at Mount Moreland immediately south of the airport. In addition I have been involved in the project in one way or another including planning of the re-habilitation since 3 August 2007.

On site during construction King Shaka International Airport Durban

After the initial earthworks were completed at the then La Mercy Airport the project was abandoned without any re-habilitation work whatsoever being implemented on site. Within a relatively short space of time weeds and grasses colonized the site and over the years many of the local grasses and grassland plants found there way onto the site.

There are as many possible methods as the days in the year, which method is correct and which method is not can probably never be evaluated, clearly on a large scale cost will be a major factor so any method that works with instead of against nature saving cost is going to be the way to go.

Before attempting to engage in rehabilitation activities one must first try to reconstruct in ones own mind the nature and annual life cycles of the grasslands of the past, some indications can still be found in the rural areas nearby that have not been affected by sugar cane farming.

In my professional opinion the method that requires the least human intervention and the maximum use of natural processes to bring about the re-creation of natural like grassland is going to be the only sensible and economical approach in the short, medium and long term. This approach certainly will not give the quickest results but will most certainly be financially justifiable and will give a good result in the end.

In most of the areas not directly associated with the airport such as the runway, terminal and service areas where earth works were undertaken the growing of sugar cane continued on a lease basis in many areas right up to this day badly depleting marginal sandy soils of the last of their nutrients until they were in many cases finally abandoned.

Albuca setosa growing in my grassland at Mount Moreland

Starting the process
Harvest the sugar cane wait for he sugar cane to start growing when there is sufficient growth to be able to deliver a lethal dose of Glyphosate spray the cane and let nature continue the process.

Annual weeds
Since the natural vegetation was destroyed and sugar cane was first planted on this land from about the 1850´s no other crop has been grown on it. Over time the sugar cane has acted as a huge trap trapping vast amounts of windblown seed of invasive alien weeds including vast amounts of annual weeds which are now stored in the soil seed bank. Due to the sugar cane inhibiting the germination of the weed seeds most never germinated those that did germinate soon died as the cane grew and robbed them of light. When the sugar cane is finally removed and the factors inhibiting the germination of the weed seed has been removed the annual weed seeds germinate in their countless millions after the first rains. Small quantities of local perennial grasses mainly Panicum maximum also germinate together with the weeds after the sugar cane is removed and they receive sunlight, once the weeds have completed their life cycles and have produced their seeds and have died the grasses have a chance to grow, to cover the ground and to produce their own seeds in turn. If left to nature after a few cycles the grasses gain the upper hand and the annual weeds almost disappear, to be an insignificant component of the resulting grassland. These same annual weeds can also be found in the few remaining natural grasslands in the immediate vicinity and when portions of these seemingly stable natural grasslands are disturbed masses of these same annual weeds germinate, slowly to be naturally suppressed by the natural grasses and other plants.

As far as attempting to eradicate annual agricultural weeds such as Bidens pilosa, Bidens bipinnata, Conyza bonariensis, Ageratum conycoides etc. by chemical or mechanical means in rehabilitation and alien plant eradication projects at the King Shaka International Airport or elsewhere in the greater Durban area is concerned, I in my professional opinion believe that it is an impossible task due to many factors beyond our control.

Ageratum conycoides the most numerous annual weed at this time of year

Inappropriate use of the herbicide Glyphosate and poor cultural practices on surrounding farmlands and derelict and poorly managed land around the city has greatly increased the number of these agricultural weeds, which release their windborne seeds to re-infesting the areas that have been cleared. In my professional opinion a good healthy cover of natural grasses and grassland plants is the only sensible solution to suppress the numbers of these unwanted weeds.

This process does however not occur where perennial alien weeds are concerned and if left to nature they generally quickly become dominant making it necessary to remove them.

If left to nature it would be many years and some not at all before many of the other grasses and grassland forbs make their way to the site therefore some help is going to be needed to help them to get on site and to help them to establish themselves.

Obtaining and growing seed
Obtaining most of the seed needed to re-introduce the required plants both grasses and forbs to the site is going to present many problems as very few are available commercially and many aer close to impossible to grow using conventional methods. Here is where a very good knowledge of our local plants in particular knowing how to grow them and introduce them into the grasslands and innovative thinking based on this knowledge is going to be vital to the success of the project.

Berkheya speciosa in my garden at Mount Moreland

With many of the plants that need to be introduced into the grassland seed is neither able to be collected in the wild or the plants do not take kindly to propagation and cultivation so a good knowledge of the plants is essential and innovative methods need to be employed to be able to introduce them into the grasslands. So as to protect my specialist know how in this area I am not going to go into any detail in this article.
The planting of certain grass seeds in particular some of the grasses with long awls such as grasses in the genus Hyparrhenia presents problems all of its own for instance they can not be planted by seeding machines because they tie themselves together in tight bunches and can from my own experience only be hand distributed unless the awls can somehow be removed from the seed without damaging the seed.

Hyparrhenia hirta growing in my grassland see the very long awls on the seed

Management of developing grassland
Management of developing grassland poses many questions as to the correct management of the emerging natural grassland for instance at some point in time additional species need to be introduced and this is going to be very difficult if there is a thick cover of Panicum maximum that dominates the landscape not allowing other grasses and Forb seeds to germinate and grow just as was the case with the sugarcane dominating the landscape before it. Fire is clearly a tried and tested method to remove the dense grass cover once per year but I believe this is both damaging and inadequate if done alone in particular on developing grasslands. Burning removes moribund grass very effectively, promotes the germination of seed, it promotes the growth and variety of grassland forbs but looses nutrient to the atmosphere. Burning certainly helps control the rampant growth of the dominant pioneer species in this area Panicum maximum.
Burning alone removes large amounts of carbon returning it back to the atmosphere in addition to other vital minerals and organic compounds which are lost to a system which has already been impoverished due to over 150 years of sugar cane cultivation.
Burning of developing grassland following the removal of sugar cane

Domestic livestock
In the natural grassland as had occurred on site before the arrival of the white man who removed it and planted sugar cane the grasslands of this region were formed by the interaction of grazing and browsing animals both wild and domesticated and the actions of man who in the absence of natural fire set fire to the grassland after the first spring rains.
It long believed that the Nguni cattle, goats and sheep arrived in southern Africa with the Nguni-speaking people, ancestors of today's Zulu, Xhosa and Swazi people.  However, recent research has revealed that the cattle were probably introduced into southern Africa by the Khoisan-speaking people in around 600 and 1400 AD this is much earlier than originally thought. The Nguni-speaking arrivals in southern Africa quickly assimilated the cattle skills and husbandry techniques of the Khoisan. 

Since then, these animals have played an important environmental role in the development of the grasslands in the areas that were settled by these people. 
It is clear in my mind that animals must be part of the equation as they not only remove grasses and other plants allowing for light to periodically reach the level of the soil which fosters a much larger varieties of plants to establish and to maintain themselves this I have observed in the wild and proven in experiments that I have performed. In addition to periodically removing unwanted top cover in controlled grassing vast numbers of organic compounds and nutrients are returned to the impoverished soil. As it is not practical to do controlled grazing with wild animals and because domestic livestock also played and important role in managing the rolling grasslands of KwaZulu-Natal before the arrival of the white man I propose the use of Nguni cattle, Nguni goats and imvu the Zulu sheep to do this valuable task for us. Large herds of wild grazing and browsing animals and pastoral activities by native tribes has clearly had a large impact on forming the natural grasslands in this region before Europeans arrived and ripped most of it up to plant mono-cultures of sugarcane which have in most regions almost completely replaced the extensive grasslands of the past.

The major perennial invasive aliens such as Lantana camara, Solanum mauritianum and Chromaleana odorata that tend to invade this site will have to be dealt with using conventional means.

The invasion of woody species will mostly be taken care of by the annual burning of portions of the grassland.

In areas with deep poor sandy soils which are readily colonized by the forest indicators, Melinis repens, Helichrysum kraussii Chrysanthemoides monilifera, Albizia adianthifolia should probably not be forced into becoming grasslands but be allowed to do what nature is clearly indicating is the natural option.

Gladiolus ecklonii growing in my grassland at Mount Moreland

Keep your plan simple if you want to be sure not to fail.
At the end of the day the final production will be determined by a combination of specialist knowledge, a good feel for the intricate workings of the natural environment, time, luck and the workings of mother nature. No man can plan such a rehabilitation project in an office in a far off place to give an exact result with absolute certainty. We are working with nature and anyone who says that they can give a precise result years down the line is either a charlatan or is God himself

Michael Hickman
Ecosystem Manager
Landscape Design Specialist


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