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Biodiversity Implications of  Riparian Home-gardens: the Case of 
Chalakkudy River Based Agro-Ecosystem in Kerala

Allan Thomas1, Usha C. Thomas2 and  N. Kishore Kumar3

ABSTRACT

 Riparian home-garden farming system are human landscapes that are sustainable, 
fulfilling the different pillars of socio-economic and environmental stability. This explorative 
study conducted in the 60 selected home-gardens in the left-right riparian banks of 
Chalakkudy river in Kerala, India casting the upper reaches and middle to lower reaches 
aimed to assess the crop diversity of tropical riparian home-gardens in terms of diversity 
index. Altogether 60 home-gardens were analysed and the Shannon – Wiener index of 
Biodiversity was found to be 1.518 in the upper riparian reaches and for the middle to 
lower reaches the average diversity index was 1.453 indicating erosion in biodiversity in  
home-gardens cascading towards middle to lower reaches of the riparian corridors.  

Keywords: Biodiversity, Landscapes, Shannon – Wiener index, Ecosystem, Species, 
Anthropogenic

Journal of Extension Education
Vol. 28  No. 2,  2016

1 & 2 Assistant Professors and 3. Professor, College of Agriculture, Kerala Agricultural University, Vellayani, 
Thiruvananthapuram, Kerala - 695 522.

Received : 30-12-2016; Accepted : 20-01-2017

INTRODUCTION

 Biodiversity describes the variety 
and array of life on earth. A common 
measurement of biodiversity is the total 
number of species found in an area 
often measured in terms of diversity 
index. High levels of ecosystem stability 
is ensured when system is more diverse 
and that lead to more resilience against 
extreme weather events, such as floods 
or drought. Biodiversity gives us choices, 
options and flexibility to help us cope 
with variability, including long-term 
habitat changes. But, riparian (describes 

the land immediately surrounding water 
sources where water strongly influences 
the immediate ecosystem) areas, that 
support high levels of natural biodiversity 
is often the niche of intervention, 
exploitation and ironically the sites 
of conservation. Historically, riparian 
areas that were important for natives 
facilitating early settlements owing to 
transitions have transcended to dwelling 
units with agricultural and riparian 
resource acting as the main resources 
for making them the ways and means of 
their life. Home-garden forms the basic 
farming production system in Kerala, a 



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constituent state of India and is present in 
all agro-ecological zones. Home-gardens 
of Kerala supports 2.76% of India's 
people (The Hindu, 2013) signifying the 
importance of this predominant type of 
agricultural production system. 

 This system with a repository of 
highly diversified valuable plants and 
animals per unit area with inclusive 
interaction through intervention by man 
has resulted in a unique combination of 
high levels of productivity, dependability 
and sustainability. The same is the 
case of Kerala riparian home-gardens. 
Hodgkin (2001) articulated that home 
gardens contribute to the conservation of 
biodiversity at the ecosystem, species and 
within species levels. Under the shrinking 
per capita land availability, dominance of 
nucleotide family structure, occupational 
shifts, resettlement after migration, 
cultural diversity, coupled with the 
intricacies of the global and market 
economy, home-garden systems are 
mushrooming and at the same time are 
facing their own challenges. The aesthetic 
and economic value of the riparian home-
garden agro ecosystem facilitates both 
agricultural and allied interventions with 
other occupational interferences which 
is uniquely different from the general 
garden-land based home-garden farming 
system. One of the major challenges is its 
rapid influence of home-gardens in the 
riparian biodiversity. Hence this study 
envisaged for a comprehensive study 

of crop diversity in the riparian home-
gardens.

METHODOLOGY

Measure of Diversity Index

Floristic richness of the Kerala home-
gardens is quite substantial (Kumar, 
2011). In this study, Shannon-Wiener 
index of diversity based on information 
theory (the information content is a 
measure of the amount of uncertainty) 
was used to calculate the diversity index 
of the home-gardens. This index was 
purposively chosen as its measure enables 
a better understanding of the structural 
configuration of home-gardens. Also, the 
whole of a home-garden as a single unit 
could be considered for the study unlike 
other cases where usually a portion of 
the ecosystem is considered by way of 
further sampling. The formula used for 
determining the diversity index was :

H'=
s

(pi log2 pi)-∑
i=1

Where,  

 H' - Shannon-Wiener diversity 
index (Di)

 pi - A proportion of total sample 
belonging to ith species

 s = number of species

Sampling

 A total of 60 riparian home-gardens 
were enumerated for its crop diversity. 

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The sixty samples were selected from the 
upper reaches, middle reaches and lower 
reaches of Chalakkudy river at every 
one km interval covering both left and 
right banks of the river covering a total 
of 30 km stretch on one side enabling 
an understanding on the agricultural 
biodiversity of the entire stretch of the 
river bank ecosystem. 

FINDINGS AND DISCUSSION

 The influence of agricultural 
activities and home-gardens that caters 
to the livelihood of farm family has an 
influence on the riparian ecosystem 
diversity.  Irrespective of the nature of 
different agroecosystem, Saikia et al. 
(2012) reported that high diversity and 
low concentration (density) of dominance 
in different home-garden categories may 

be due to variations in anthropogenic 
pressure in different home gardens. 
Hence, region wise Shannon diversity 
index (H') was worked out for a proper 
understanding of the diversity level 
of riparian home-gardens indirectly 
throwing light to the biodiversity status 
of the Chalakkudy riparian tracts. The 
results are enumerated and discussed 
under the following subheads.

Region wise Diversity index (Di) of 
riparian home-gardens in the upper 
reaches and mid to low reaches

 The results of region wise diversity 
index presented for sixty samples 
of riparian home-gardens selected  
randomly from the upper and lower 
reaches are presented in Table 1. 

Table 1.  
Biodiversity Index of Riparian Home-Gardens in the Upper and Mid to Lower  

Reaches of Chalakkudy River
N=60

Sl.No.
Riparian 
Reaches

Shannon Diversity index (H') Mean H'
Standard 
Deviation

1
Upper 
(n=10)

1.235 1.614 1.674 1.457 1.414
1.518 0.168

1.709 1.765 1.366 1.45 1.491

2
Middle to 
lower  
(n= 50)

1.492 1.161 1.58 1.292 1.573

1.453 0.201

1.350 1.384 1.632 1.522 1.593
1.193 1.243 1.193 1.632 1.502
0.873 1.535 1.537 1.696 1.182
1.177 1.362 1.537 1.215 1.720
1.254 1.649 1.561 1.579 1.592
1.425 1.114 1.633 1.472 0.932
1.614 1.521 1.736 1.432 1.636
1.337 1.666 1.449 1.553 1.535
1.481 1.599 1.653 1.529 1.539

Biodiversity Implications of  Riparian Home-gardens: the Case of Chalakkudy River Based Agro-Ecosystem in Kerala



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Values  in Table 1 reveal that the biodiversity 
was more in the home-gardens of upper 
reaches (mean Shannon H'=1.518) as 
against the biodiversity measures of 
mid to lower reaches wherein the mean 
Shannon H' value was 1.453.

 The values of the table also revealed 
that the Shannon biodiversity (H') of 
home-gardens ranged from 1.235 to 1.765 
in the upper riparian reaches; wherein 60 
per cent (Table 2) of home-gardens were 
categorised as low biodiversity home-
gardens with mean as the check. In case 
of home-gardens stretching across the 
mid to lower reaches of the tributaries of 
Chalakkudy river,  the Shannon H' value 
ranged between 0.873 and 1.736 and 52 
per cent of riparian home-gardens were 
categorised as higher biodiveristy home-
gardens (52%) with its mean value as the 
check as presented in Table 2.

 The values from Table 1 and 2  
reveal that, when more percentage of high 
biodiversity home-gardens was found 
in lower reaches of the stream, whereas 

more percentage of lower diversity home-
gardens appeared in the upper reaches. 
This could be because more number of 
home-gardens appeared in mid to lower 
reaches of the river and were small 
holdings when compared to the home-
gardens in the upstream, that were 
less in number and larger in size when 
compared to the riparian home-gardens 
in the lower reaches. Also, the smaller 
holding size of home-gardens may have 
more number of taxonomically distinct 
crops in position  as compared to that of 
larger holding size of home-gardens that 
may include more number of species of 
a dominating variety with high economic 
value.

 Region wise Diversity index (Di) of 
riparian home-gardens in the right and 
left banks of Chalakkudy river.

 Chalakkudy river is unique with 
man intervention through the river 
diversion project splitting the river into 
right and left banks. This has led to unique 
forms of human landscapes dominated 

Table 2.  
Categorisation of Region wise Diversity Index (H’) of Riparian Home-Gardens (Upper and 

Mid to Low Reaches)

Sl.No. Category
Upper Reaches

n=10

Middle to Lower 
reaches

n=50
1 Mean H' 1.518 1.453

2 High biodiversity home-gardens 4 (40%) 26 (52%)
3 Low biodiversity home-

gardens
6 (60%) 24 (48%)

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with home-gardens. The biodiversity 
index of home-gardens in both banks 
were worked out and categorised. The 
results of the same are presented in Table 
3 and Table 4 repectively.

 The results of region wise 
diversity index reveal that the 
biodiversity was more in the left 
banks (mean Shannon H'=1.518) 
than the right banks wherein the 
mean Shannon H' value was 1.453. 
The values in Table 3 reveal that the 
biodiversity H' range of home-gardens 
in the right banks ranged from 1.161 
to 1.674; wherein 55 per cent (in 
table 4) were home-gardens with low 
biodiversity with mean as the check.

 In case of home-gardens 
stretching across the left banks of 
chalakkudy river, the Shannon H' 
value ranged between 0.873 and 
1.765. The values in Table 4 revealed 
that 51.67 per cent of riparian home-
gardens were categorised as higher 
biodiveristy home-gardens with its 
mean value as the check. Hence, it 
could be inferred from Table 4 that 
both banks consisted of more number 
of high biodiversity home-gardens. 
This does not mean that majority of the 
home-gardens were highly diversified 
as this kind of categorisation as high 
and low has been made based on the 
mean value of its overall biodiversity 
as a check and moreover such a 

Table 3.  
Biodiversity Index of Riparian Home-Gardens in the Right and Left Banks  

of Chalakkudy River
N=60

Sl.No.
Riparian 
reaches

Shannon Diversity index (H')
Mean 

H'
Standard 
Deviation

1

Right bank 

(n=20)

1.235 1.614 1.674 1.457 1.414

1.518 0.168
1.492 1.161 1.580 1.292 1.573
1.35 1.384 1.632 1.522 1.593
1.193 1.243 1.193 1.632 1.502

2

Left bank

(n= 40)

1.709 1.765 1.366 1.45 1.491

1.453 0.201

0.873 1.535 1.537 1.696 1.182
1.177 1.362 1.537 1.215 1.72
1.254 1.649 1.561 1.579 1.592
1.425 1.114 1.633 1.472 0.932
1.614 1.521 1.736 1.432 1.636
1.337 1.666 1.449 1.553 1.535

1.481 1.599 1.653 1.529 1.539

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type of conclusion can be made only 
while making comparisons with other 
studies on biodiversity.

H' ranges from 1.235 to 1.765 in 
the upper riparian reaches with the 
average H' of 1.518 and for the middle 
to lower reaches the mean H' value 
ranged between 0.873 and 1.736 with 
an average diversity index of 1.453 is 
an indication of erosion of biodiversity 
in  home-gardens cascading towards 
middle to lower reaches of the 
riparian corridors. This highlights the 
fact that anthropogenic interventions 
were more in the mid to lower reaches 
indicating the necessity of policy 
intervention to regulate unscrupulous 
interventions that affect biodiversity 
adversely, and there is a need to 
reclaim the biodiversity of the riparian 
region with more sound agro-forestry 
programmes.

 The better H' in the upper 
reaches revealed that irrespective 
of the size of holdings the home-

gardens tends to preserved the 
maximum taxonomically distinct 
variance within the region. This also 
has a reflection of the complementary 
exploitation of habitat resulting in 
more complete capture of resources. 
Such complementarities have been 
reported by Campbell et al. (1991).  
In addition to these, influence of 
management has also been reported 
by Thomas (2004).  As the middle 
to lower reaches were more dense, 
home-garden farmers could have 
being intervened to capacitate 
his garden with more number of 
specific imperative and remunerative 
species, intentionally and thus 
lowering the biodiversity in the  
lower reaches . 

 Considering the nature of 
selection of home-gardens for the 
study these values cannot be a 
representative of the home-gardens 
for whole of Kerala as these were 
home-gardens selected from a specific 

Table 4.  
Categorisation of Region wise Diversity Index (Di) of Home-Gardens in the Right  

and Left Banks

Sl.No. Category
Right Bank

n=20
Left Bank 

n=40
1 Mean H' 1.518 1.453
2 High biodiversity home-

gardens
11 (55%) 31 (51.67%)

3 Low biodiversity home-
gardens

9 (45%) 29 (48.33%)

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type of useful and a unique type of 
agro-ecosystem that is riparian in 
its characteristics. However, there 
was a notion that agroforestry crops 
are on the decline in home-gardens 
which was a clear indication of cut 
and removal of the same for inclusion 
of economic dominant crops or as a 
result of spatial pressure due to the 
constraints of family compulsions. 
This is resulting in the overall decline 
of biodiversity in home-gardens which 
in real is negating the thinking of Das 
and Das (2005) who had described 
that home-gardens are the sites of 
conservation of a large diversity of 
plants both wild and domesticated, 
because of their multipurpose uses 
to the households.  Riparian home-
gardens need to be studied extensively 
and continuously as these are the 
owners and conservers of this river 
based ecosystem that is being widely 
exploited by man in multiple ways. 

CONCLUSION

 The study has shown that there 
is a trend towards depleting biodiversity 
in the home gardens of middle to lower 
reaches of Chalakkudy river.    River 
based home-gardens are just not natural 
reservoirs or repositories of terrestrial 
biodiversity, but also the aquatic 
biodiversity. The diversity of crops with 
primary home-garden components along 
with vegetation, livestock, fisheries and 

other specialisations enables continuous 
produces/products and reduces the 
production risks that in turn keeps up 
the motivation level of farmers to try 
out with more of commodity crops-non 
commodity crops combination. This 
will ensure remunerativeness as well as 
maintain or augment biodiversity of the 
riparian agroecosystem. 

REFERENCES

Campbell, D.D., Grines, J.P. & Mackey, 
G.N. (1991).  A Trade off Between Scale 
and Precision in Resource Foraging. 
Ecology 87:532-538

Das T. & Das A. K. (2005). Inventorying 
Plant Biodiversity in Home-gardens:  
A Case Study in Barak Valley, Assam, 
North East India. Current Science, 89 
(1): 155-163.

Hodgkin. (2001). Home Gardens and 
the Maintenance of Genetic Diversity. 
Home Gardens and in situ Conservation 
of Plant Genetic Resources in 
Farming Systems, Proceedings of 
the Second International Home 
Gardens Workshop, 17–19 July 2001, 
Witzenhausen, Federal Republic of 
Germany. p: 14-18.

Kumar, B.M. (2011). Species Richness 
and Aboveground Carbon Stocks in 
the Home-gardens of Central Kerala, 
India. Agriculture, Ecosystems and 
Environment, 140: 430–440.

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Saikia, P.S., Bora, D., Goswami, A., 
Mudoi, D.K & Gogoi, A. (2012). A 
Review on the Role of Azospirillum 
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1102

The Hindu. (2013 May 18) Kerala 
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Thomas, A. (2004). Technology 
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Journal of Extension Education