ISIS Report 09/10/06
Circular Economy of the Dyke-Pond System
Dr. Mae-Wan Ho finds
strong allies for her idea on sustainable systems as closed cycles modelled
on the organism (Dream
Farm 2 - Story So Far) during her recent visit to China , especially
in a land-water farming system developed over the past two thousand years
A fully referenced
and illustrated version of this report is posted on ISIS members’ website.
Getting the most from land and water
The clouds and mists cleared as we prepared to land in Guangzhou,
and a remarkable landscape came into view. Like a mosaic of silver mirrors
embedded in emerald, hundreds, if not thousands of ponds filled the spaces
between the Pearl River tributaries as they meandered and fanned out into
the South China Sea.
The ponds were predominantly
narrow rectangles stacked broadside on, with shorter rectangles, squares,
and irregular shapes pressed into service to fit the topography. The main
effect was to leave cultivated strips of land and the occasional fields between
adjacent bodies of water.
The Pearl River Delta of
South China, sprawling over 12 000 km2,
is famous for its dyke-pond system of fish farming combined with the cultivation
of crops . It contains one of China’s richest and most densely populated
agricultural areas, supporting an average of 17 persons per hectare.
The dyke-pond system evolved
over the past two thousand years, perfected by generations of Chinese farmers
into a ‘circular’ economy of intensive agriculture integrated with the polyculture
of carps and other freshwater fishes, on a geographic and economic scale unrivalled
elsewhere in the world. It depends on maximising internal inputs between land
and water, optimising the efficient use of resources while minimising wastes.
The director of the Guangzhou
Institute of Geography, Prof. Zhang Hongou, stressed that ‘circular economy’
is a guiding principle in mainstream Chinese thinking, as opposed to the linear
economy of the West. Perhaps that is at least partly why the Chinese economy
has been growing mostly in double figures over the past decade.
Guangzhou Institute of Geography
was established in 1958 as part of the Chinese Academy of Sciences,
and in 1999, received recognition from the Chinese government as one of Ten
National Distinguished Organisations. Among its accolades is the scientific
study of the dyke-pond system pioneered by Prof. Zhong Gongfu and his colleagues
in the 1970s, and its successful extension for flood control and improved
land use (see later).
The Institute also researches on regional development in Guangdong, tropical
and Chinese geography, environment and ecology, remote sensing and land use.
It runs a web resource for remote sensing and environmental protection, and
publishes a journal.
The dyke-pond system
In the late 1980s when Guangzhou Institute first carried out the survey,
the main dyke-pond area covered 86 632 ha between the two major Pearl River
tributaries, Xijiang and Beijiang, of which 30 321 ha (35 percent) were fishponds,
combined with the cultivation of mulberry (10 395 ha, 12 percent) or sugar
cane (15 593 ha, 18 percent). The remainder 30 322 ha (35 percent) was mainly
irrigated rice (25 percent) and a variety of mixed or miscellaneous agriculture
that includes dykes specialising in fruit trees, vegetables or decorative
plants and flowers .
The pond is the heart of the system. To produce a pond, soil is excavated
and used to build or repair the dykes surrounding it. Before it is filled
with water, the pond is prepared by clearing, cleaning and fertilization with
quick lime, tea-seed cake and organic manure from livestock kept on the dykes.
Most ponds are rectangular, 0.4 to 0.6 ha in area and 2 to 3 m deep. The dykes
are usually 6 to 10 m wide, and extend 0.5 to 1.0 m above the pond surface.
Various fish species live at different pond depths, and have different feeding
habits, thereby making full use of the water and the pond ecology. The typical
polyculture is a combination is the “four big family fish”: grass carp (Ctenopharygodon
idellus), silver carp (Hypopthalmicths molitrix), big head carp
(Aristichthys nobilis) and common carp (Cyprinus carpio), requiring
little or no external input.
The pond mud, much enriched
in nutrients, serves as fertiliser for crops. Ponds are drained two or three
times a year, and the mud at the bottom is dredged up to put on the dykes,
thereby raising and repairing the dykes and restoring the depth of the pond.
Pond mud is also used for mushroom cultivation. Mushrooms are often cultivated
on the floor of the silkworm shed in winter, the off-season for silkworm production.
After the final crop of mushrooms has been harvested, the mud-bed is used
to fertilize vegetables, fruit trees and grasses.
The pond is filled with
river water. Water also enters directly as rain and through runoffs from the
dykes. Water leaves the pond via the pond drainage outlet in controlled discharges.
It is also lost through evaporation and transpiration, via seepage into the
dykes, and through being removed at regular intervals to ‘fertigate’ the crops
growing on the dykes.
Livestock is an important
link in the circular economy. Pigs, chickens and ducks are reared on the dykes,
to provide manure to fertilise the fishponds, to encourage the growth of plankton
that feed the fish.
Most dyke crops are fed
directly to the fish, such as elephant grass for the grass carp, or else to
the livestock, such as forage crops for pigs.
With a tropical to subtropical
climate, the dyke-pond area is well endowed with sunshine and rainfall, and
hence extremely productive, especially with a system that recycles and transforms
all the “wastes” into nutrient resources.
The circular economy can be quite complex [1-3]. I have
drawn a diagram of a simple system involving mulberry cultivation. Mulberry
leaves are picked to rear silkworms, from which silk cocoons are harvested,
while the wastes of silkworms are used to fertilise the pond to feed the fish.
With only pigs and vegetables included, there are at least 11 cycles in the
diagram varying in length from two to five links.
The external energy input
is minimal, and consists of mainly labour and the energy expanded to make
farming implements, housing and equipment for rearing silkworms, and machinery
and energy to aerate the fishpond and to dredge it. The major energy input
by far, of more than 99 percent , is sunlight, and it is free.
There are numerous harvests,
fishes, silk cocoons and vegetables being the major ones for the system depicted,
pigs would be a minor harvest. Some harvests would include livestock such
as chickens and ducks as well as mushrooms.
Fish sales contribute the
largest source of income to the region’s agricultural sector, some 50 percent
of the total fish production of Guandong Province and 80 percent
of the nation’s export in live fish.
Figure 1. Circular economy of dyke-pond
Since the late 1970s, the traditional dyke-pond system of the Pearl River
Delta has been undergoing dramatic changes. The first was a major shift from
a collectivist to household production as part of the major rural reforms
implemented throughout China. The second involves an intensification of production,
a gradual supplementation of internal inputs with external inputs and a move
away from the previously sustainable circular economy.
Dyke-pond system and flood control
About 1 000 years ago, the coastline of the Pearl River Delta was very
different. The delta of Zhujiang, the most northern of the three major tributaries,
met the delta of Xijiang, the most southern tributary , and the lowlands
were neither widely nor continuously cultivated on account of flooding and
the presence of sulphuric acid soils. The villagers depended heavily on capturing
and collecting marine, riverine and wetland resources. At higher elevations,
however, fruits were cultivated, especially litchi (Litchi chinensis) and longan (Euphoria longana).
During the mid-fourteenth century, water control measures were started in
the lower-lying areas. Small watercourses were dammed and dykes created to
make fishponds. Ponds were dug to drain the marshes and natural ponds in order
to create agricultural land, and the excavated soil was used to construct
the dykes. The fishponds were stocked with carp fry naturally occurring in
The first commercial crops to be grown on the dykes were litchi and longan,
but there were no conscious effort to integrate pond and dyke ecology until
much later. By the 1620s, mulberry was widely cultivated on the dykes and
the economic returns from the integrated mulberry dyke-fish pond systems were
found to be greater than fruit-tree cultivation.
Thus, the circular economy
of the dyke-pond system evolved out of a flood control measure, and it has
been used effectively for the same purpose since. It will have worldwide applications
as sea level rises in coastal areas, and in flood-prone areas fed by melting
ice and glaciers.
Outside the core region
of the traditional dyke-pond system, there remains in Guangdong
Province some 200 000 ha of flood-prone lowland, including the areas along
the lower reaches of the main rivers and the coastal lowlands of the Zhujiang
Delta. Most of these lowlands are seasonally flooded to depths of 1 to 1.5
m, and sometimes as much as 3 m of river and rainwater, exacerbated by a history
of deforestation in the watersheds of Guangdong Province.
Since the 1950s, various
measures have been taken to manage the flood-prone lands: building reservoirs
and canals, contour ditching, sluice systems to raise the water in canals
and to drain floodwaters; establishing a network of pumping stations to drain
water from the flood plains into the canals; and reforestation in the highlands.
In the coastal regions, earthern dykes were reinforced or replaced by concrete
to improve resistance to typhoon-driven high hides, irrigation and drainage
systems were separated by tunnels to lower the water-table, an electric pumping
network was installed for drainage and irrigation and low-lying land was elevated
by spreading soil.
These measures succeeded
in reclaiming much of the flood-prone lowland, making agriculture possible
and improving public health. Schistosomiasis (a disease spread by a parasitic
worm) was eradicated. However, some 30 percent of the lowland by the rivers
in Guangdong still remained to be brought into sustained productive
use. This consists of widely scattered land in small pockets, or especially
low-lying and not amenable to reclamation by other measures. Similarly, in
the coastal zone, despite the use of pumping stations for drainage and irrigation,
crops yields remained low owing to high water tables and salination. The dyke-pond
system has proven effective in transforming those waterlogged lowlands into
productive sites. Fishponds were dug and the excavated sediment used to construct
raised dykes and fields.
Scientists in the Guangzhou
Institute of Geography started a research project in the early 1970s supported
by the United Nations University [1-3, 5]. They established an experimental
station in Shunde County in the heart of the dyke-pond region
to study energy flow and material cycles in the newly established dyke-pond
systems, and were able to document the successes .
Turning water-logged lowlands into productive dyke-pond systems
Deqing County, 240 km west of Guangzhou is one of
the most seriously eroded regions in the Province. Many watercourses got silted
up and the streambeds became higher than the surrounding fields, with the
result that about 10 percent of the fields were waterlogged. Two tracts of
lowlands were selected for introducing the dyke-pond systems in 1979.
The first, a 19 ha tract called Liangqintang normally yielded a single rice
crop yearly, and was used for fish culture during the high-water season. Productivity
was low, no more than 3.75 tonnes of rice/ha and 0.75 tonnes of fish/ha. Often,
production failed altogether; and people referred to it as “a tract of three
harvests in ten years”.
The tract was converted to a dyke-pond system growing bananas and elephant
grass (for fish feed). A small distillery and pigsties were constructed next
to the pond. The distiller’s grain was fed to the pigs and the pig wastes
emptied into the pond. The 1981 fish harvest reached 3.0 tonnes/ha. In 1982,
the total harvests (over all 19 ha) jumped dramatically to 125 tonnes of fish,
150 tonnes of bananas, and 75 tonnes of pork, not counting large amounts of
vegetables. The net income for 1981 was already 7.6 times higher than in 1978
before the project began.
The second site selected in Deqing County was a tract of 2.7 ha of seasonally
flooded lowland along the Xijiang River in Quianhoujie Village. It was converted
into a mulberry dyke-pond with some vegetables. A pigsty was constructed near
the pond. Mulberry leaves were fed to silkworms, the silkworm excrement and
pig manure were emptied into the pond. The pond mud was used periodically
to fertilize the dyke soil. By 1982, the net income increased 200 percent
from 1981; and that in 1983 was 60 percent higher than 1982.
Doumen County, located in the southwestern part
of the Zhujian Delta, has 40 percent of its land at 0.2 to 0.8 m below sea
level. Electric pumps are commonly used to remove water from low-producing
rice and sugarcane fields. A variety of dyke-ponds were successfully installed
in the late 1970s, which then spread to the whole country.
The low-lying fields at Anfenwei in east Doumen are inundated
annually for several months. Since 1979, 6 ha of fish ponds were dug to a
depth of 2.5 to 3 m and the mud removed was spread over the fields at an average
rate of 750 m3/ha/year. After several
years, the fields were raised to sea level and no longer water-logged. The
fields were planted in a rice-sugarcane rotation and interplanted with vegetables.
Pigs and poultry were raised close to the ponds and their excrement emptied
into the ponds. Rice yields increased from 6 tonnes/ha/year to 7.5 tonnes/ha/year,
and 4 tonnes of fish were harvested in addition to pigs and poultry. Electricity
bills were reduced 20 to 30 percent annually because of decreased need for
drainage pumping. Up to 1982, at least 700 ha of fish ponds have been dug
in the entire county, and about 10 000 ha of low-lying fields have been elevated.
The Chenhai-Raoping district of 48.6 km2
situated between Changhai and Raoping Counties in east Guangdong Province
resulted from a reclamation and farming project completed in 1971. However,
much of the area is still under water.
A research team from the
Guangzhou Institute of Geography designed an integrated development programme
including the dyke-pond system , and put the programme into operation in
1983. By 1987, remarkable improvements were achieved in all aspects, including
the dyke-pond system. A total of 262 ha of ponds had been constructed yielding
5.805 tonnes fish/ha at a value of 6.08 million Yuan/year. Considerable amounts
of vegetables and forage crops were also harvested from the dykes.
Dyke-pond system under pressure from industrial growth
These remarkable successes were not followed up, however. Practically
all the academics involved in the dyke-pond projects had soon retired or were
near retirement, and market forces and other pressures of rapid industrialisation
came into play.
“China has developed too quickly, at 10 to 20 percent growth
in GDP a year,” the Institute director Prof. Zhang said, “This has placed
agriculture under great pressure. Industrialisation has led to a decrease
in land available for agriculture, and the pressure to produce more from less
land has resulted in increased pollution.”
The professors of the dyke-pond system, Zhong Gonfu, Wu Houshui,
Deng Hanzeng and Liang Kuo Ziao, now all retired, came to meet with us to
explain their work, thanks to the tireless efforts of Prof. Zhong Ying, daughter
of Zhong Gongfu, who acted as our guide and mentor throughout the most enjoyable
and productive five days we had in Guangzhou. She and Prof. Wu Houshui accompanied
us for a day tour to important sites, including the dyke-pond region, or what
is left of it today.
The experimental station where they carried out precise measurements on energy
and material flows has long since gone, and many of the sites they surveyed
or worked on have disappeared. Prof. Wu Houshui estimates that perhaps half
of the pond-dyke area may have gone under the pressure of industrial development.
All agreed that there was a need for projects like Dream Farm 2  (Dream
Farm 2 - Story So Far) to integrate biogas production and other renewable
energies with sustainable agricultural production. Prof. Zhang Hongou was
very receptive to the idea, and we agreed to develop future collaborations.
Industry, ingenuity and market forces
The success of the dyke-pond system owes a lot to the particular combination
of ingenuity and industry of Chinese farmers, and it is still much in evidence
The farmers are extremely
skilled at maximising the use of space, time and resources; but a commitment
to hard work is also necessary. Gourds and melons are trained on trellises
overhanging ponds and drainage ditches, and crops are planted together so
that sun-loving species provide shade for those requiring it. Plantings are
timed so that several harvests are obtained from the same piece of land.
Where sugarcane is planted,
the main product is sugar, but the young leaves are fed to fish and pigs,
and old leaves used to shade vegetable gardens. Refinery wastes are returned
to the dyke pond as fish and animal feed. Bamboos are often planted to provide
poles for construction and materials for making baskets, traps, screens, trellises
and frames. Bamboo wastes are also used as fuel.
During our all too brief
tour of the dyke-pond region, we met a farmer by the roadside, knee deep in
the drainage ditch, dredging up the black mud from the bottom of the ditch
to put onto her vegetable garden that reached right up to the water margin
of the ditch. Her garden is a perfect example of the intensive and ingenious
use of limited land. The Chinese government gave her one fen of land (one-tenth
of a Chinese mu = 0.0667 ha), but she grows enough to feed her own family,
with plenty left over to sell on the market. She offered to invite us to lunch
on the spot, on hearing that we were from London in the UK;
unfortunately we were unable to accept her due to the lack of time.
Other ingenious use of the
pond was to raise ducks, the faeces of which go directly to fertilise the
fish and we saw plenty of that.
Fish farming can be very
profitable, but is also increasingly at the mercy of market prices. Chinese
love good food to extreme, and restaurant meals are a must for any visitors
(fortunately for us). The foyer of restaurants in Guangzhou
is typically filled with aquariums exhibiting live fish that you can choose
for your meal with the price per catty clearly marked, and it is considered
impolite to choose cheap fish for the guests. Any fish that became too available
would become cheap, no matter how tasty it is, and hence could bankrupt the
fish farmer overnight.
We saw signs of intensification
of fish farming that was clearly unsustainable. A worker was hired to feed
cut-up frozen sea fish to some highly priced carnivorous fish reared in a
pond owned by someone else, and the feeding shed was filled with “fish medicines”
to control diseases and parasites probably brought in by the feed, and by
the pond being too heavily stocked. The price of the feed was 1.50 Yuan per
catty, while the fish in the pond was fetching $15 per catty in the market.
High stocking rates of fishponds,
external feeds, diseases, and “fish medicines” all contribute to fouling the
pond water, which becomes a serious source of pollution when drained into
the rivers and lakes. Intensive fish farming has indeed become an ecological
problem in search of a solution, and Dream Farm 2  could well offer a way