It gives idea about the threats to biodiversity due to the Agriculture run-off.

1. Agricultural runoff – Threats to biodiversity

2. INTRODUCTION
The global population is projected to reach 9.8
billion people by 2050. (UNDESA, 2017)
Population growth and changes in consumption
patterns, require the production of more food.
Agriculture supports the construction and
development of a national economy.
At present 11 percent (1.5 billion ha) of the globe's land surface (13.4 billion ha) is used in crop
production. (Mateo-Sagasta et al., 2017)
Agricultural land (% land area) in India was reported at 60.43%. (World Bank collection, 2018)
The farmers have adopted the modern inputs like use of chemical fertilizers and pesticides,
herbicides, insecticides to increase output per unit of land.

3. AGRICULTURE RUNOFF
Agricultural runoff is surface water that flows from farms with rain, meltwater and irrigation. Its
main sources of excess water are from irrigation and rainfall. (Xia et al., 2020)
This runoff can contain pesticides, sediment (soil particles), nutrients and heavy metals, salts,
pathogens and chemicals which can contaminate sources of water.
Agricultural runoff happens when agricultural activities are not well-managed or because of
improper management of animal feeding operations, plowing excessively, poorly executed
application of pesticides, irrigation water and fertilizer.
It is typically a nonpoint source Pollution (NPS), which means it is hard to exactly locate where the
pollution comes from. Eg - Sediments, nutrients and pesticide
In USA, agricultural nonpoint source pollution is considered the dominant source of nutrients in
lakes and streams.

4. CONTD.
According to the U.S. National Ocean Service, 80 per cent of pollution of the marine environment
come from the land, and nonpoint source pollution from agricultural runoff is the major
contributor.
(National Water Quality Inventory, 2000) reported that agriculture (NPS) pollution is the leading
source of water quality impacts on rivers and lakes, the second largest source of impairments to
wetlands, and a major contributor to contamination of surveyed estuaries and ground water.
(Wiens, 1980)
Impacts from agricultural activities on surface water and ground water can be minimized by using
management practices.

5. HOW RUNOFF OCCURS?
Small soil particles dislodged by the rain drops fills the block soil pores in the fields
Resulting in decrease in infiltration
As excess precipitation occurs, the surface soil along with the agri chemicals & other inputs will flow
with rain water
ultimately drains to the sea

6. RAINFALL-RUNOFF RELATIONSHIPS
If precipitation rate is greater than
infiltration capacity, surface runoff
occurs
If precipitation rate is less than or
equal to infiltration capacity, no
surface runoff occurs.

7. CONTAMINANTS- AGRICULTURAL RUNOFF
Nutrients
 Farmers apply nutrients such as phosphorus, nitrogen, and potassium in the form of chemical fertilizers and
organic fertilizers as well as animal excreta and normally found in water as nitrate, ammonia or phosphate.
 However, when nitrogen and phosphorus are not fully utilized by the growing plants, they can be lost from
the farm fields and negatively impact air and downstream water quality.
 This excess nitrogen and phosphorus can be washed from farm fields and into waterways during rain events
and when snow melts, and can also leach through the soil and into groundwater over time.
Pesticides
 These are used to kill agricultural pests. These chemicals can enter and contaminate water through runoff,
and atmospheric deposition.

8. VALUE OF GLOBAL PESTICIDE TRADE

9. CONTD.
 Herbicides - 2,4-D, 2,4,5-T, Atrazine, Glyphosate, Paraquat , Diquat, Chlorophenoxy, Acetanilides
 Insecticides - Organophosphate - Parathion, Malathion, Timet
Carbamate - Aldicarb
Organochlorine - DDT (Dichloro-diphenyl-trichloroethane), methoxychlor, dieldrin, chlordane
 Fungicides - Thiocarbamates, Cupric salts, Triazoles
Organic manure
 Animal manures and sewage sludges (biosolids) are the main organic fertilizers
 Organic matter carried by runoff water serve as food source of bacteria --substantially shoots up BOD
 The discharge of organic matter also increases the risk of eutrophication and algal blooms in lakes, reservoirs
and coastal areas.

10. CONTD.
Metals
 Heavy metal contaminants from sources such as fertilizers and manure. E.g. arsenic (As), chromium (Cr), lead
(Pb), mercury (Hg), nickel (Ni), and vanadium (V), cadmium (Cd) .
 Heavy metals in biosolids may be found in the inorganic form or may be organically complexed, which could
affect their chemical reactions in soil.
 These heavy metals may accumulate in soil with repeated fertilizer applications.
Salts
 Salts may form on agricultural land due to evaporation of mineral rich irrigation water. E.g. ions of sodium,
chloride, potassium, magnesium, sulphate, calcium.
 Irrigation can mobilize salts accumulated in soils (leaching fractions), which are then transported by drainage
water to receiving water bodies and cause salinization.
 Whenever salinity increases, the biodiversity of microorganisms, algae, plants and animals declines

11. CONTD.
 Inefficient irrigation can cause water quality problems. In arid areas, for example, where rainwater does not
carry minerals deep into the soil, evaporation of irrigation water can concentrate salts. (USEPA, 2005)
Sedimentation
 Soil that is washed away from fields. Rain water carries soil particles (sediment) and dumps them into
nearby lakes or streams.
 In addition, other pollutants like fertilizers, pesticides, and heavy metals are often attached to the soil
particles and wash into the water bodies.
 Sediments can cover and destroy fish spawning beds, clog fish gills, and reduce useful storage volume in
reservoirs.

12. CONTD.
Pathogens
 Some pathogens can survive for days or weeks in the animal waste discharged onto land and may later
contaminate water resources via runoff (FAO, 2006; WHO, 2012)
 Bacteria and pathogen indicators. E.g. Escherichia coli, Salmonella spp. and Clostridium botulinum (Christou,
2011)
Emerging pollutants
 Pollutants such as antibiotics, vaccines, growth promoters and hormones etc. these can reach water via
leaching and runoff.

13. WORLDWIDE FERTILIZER USE
 The N and P fertilizers
have been used most
widely in the world.
 According to statistical
data (FAO, 2015) the
world’s average use of N
fertilizer per cropland
area has reached
68.6 kg/ha, and
30.1 kg/ha for P.
(Linong et al., 2021)

14. THREATS TO BIODIVERSITY

15. EUTROPHICATION
Eutrophication is the process by which an entire body of water, or parts of it, becomes
progressively enriched with minerals and nutrients.
Due to excess of nutrients ( P and N ) into aquatic system via agricultural runoff. (Sechrest and
Brook, 2002)
• Uncontrolled algae growth (Harmful algae bloom), plankton in the water body are signs of this
process.
• blocking light from reaching other organisms.
• Kill aquatic organisms due to depletion of oxygen levels
• It produce allelopathic or toxic compounds . For example, the trophic transfer of cyanotoxins,
leads to physiological and behavioural impairments (Ferrao-Filho & Kozlowsky-Suzuki, 2011)
• create foul taste and odour in drinking water

16. CONTD.
The large “cyanobacteria mat” in Taihu Lake,
caused the closing of a drinking water plant in
Wuxi, leading to a crisis afecting millions of
people .
 At the same time, continuous input of heavy
metals and persistent organic pollutants (POPs)
from agricultural runoffs can easily accumulate
in organisms to pose various health risks (e.g.,
pollution of drinking water). (Xia et al., 2020)

17. CONTD.
 Agricultural runoff has caused major issues for local ecosystems in
the Ohio River Basin.
 The Ohio River is one of the largest and most important rivers in the
continental United States. it has been a source of food and water for
centuries, is considered to be globally outstanding by virtue of its
high fish and invertebrate diversity (Abell et al. 2000).
 But the widespread use of fertilizer, herbicides, and pesticides in
agriculture has caused chemical runoff into the Ohio River
watershed, damaging local ecosystems.
 Increased algal populations in the waters of these streams and rivers
can cause changes in water chemistry which can affect the fish and
macroinvertebrate communities

18. FORMATION OF DEAD ZONES
‘’Dead zone” or “hypoxia” refers to low-oxygen areas in the world’s lakes and oceans, and is so
called because very few organisms can survive in hypoxic conditions.
A dead zone occurs as a result of eutrophication , when the algae die, their decomposition uses
all the available oxygen in the water, creating “dead zones,” which are uninhabitable for fish and
other aquatic life.
Dead zones occur in coastal areas around the nation and in the Great Lakes.
The majority of the world’s dead zones are along the eastern coast of the US, and the coastlines
of the Baltic States, Japan and the Korean Peninsula.
The second largest dead zone in the world is located in the U.S., in the northern Gulf of Mexico
Scientists have identified 415 dead zones worldwide.

19. CONTD.
One of the most well-known example of eutrophication - dead zone in the Gulf of Mexico is
approximately 6,334 square miles, or equivalent to more than four million acres of habitat
potentially unavailable to fish and bottom species. (NOAA, 2021)
It is the result of fertilizers from farms across the Midwest draining into the Mississippi River.
• Dead zones in lakes reduces the available habitat for aquatic life
• forces competition between many species in small areas, ultimately leading to the lake’s loss of
biodiversity as these oxygen-free zones are fatal to animals that live on or in the seabed.
The average hypoxic zone over the past five years is 5,380 square miles.
It threatens the Gulf fishing industry.

20. Source: NOAA

21. TOXICITY
The organo chlorine pesticides like DDT will directly affects the metabolism of fishes & transferred
through the food chain by Bioaccumulation and Biomagnification.
Toxicity effects of gross pesticide pollution and chronic, longer term effects.
DDT is highly persistent in the environment and its soil half-life for DDT is from 2 to 15 years.
In surface water, DDT will bind to particles in the water, settle, and be deposited in the sediment.
DDT is taken up by small organisms and fish in the water. It accumulates to high levels in fish and
marine mammals (such as seals and whales), reaching levels many thousands of times higher
than in water, leading to adverse health effects.
DDT is highly acutely toxic to fish and affects membrane function and enzyme systems.

22. CONTD.
DDT affects juvenile aquatic invertebrates more than
adults
DDT causes reproductive, developmental, cardiovascular,
and neurological changes in aquatic invertebrates .
It blocks normal nervous system of fish eating birds.
(eagles, Ospreys, Pelicans etc.)
Interferes with calcium deposition during the formation of
egg shell in marine birds and causes eggshell thinning.
Agricultural runoff mixed with pesticides from the nearby
farmlands to wetlands is another major threat in
Beeshazari Lake, Nepal. (Kafle & Savillo, 2009 ; Shrestha et
al., 2020)

23. (Tyohemba et al., 2021) examine the potential exposure and accumulation of currently used
herbicides in two species of fish from Lake St Lucia, a global biodiversity hotspot located in South
Africa.
Herbicide residues were detected in all samples analysed, with total concentrations ranging from
44.3 to 238 ng g− 1 (Clarias gariepinus) and 72.2–291 ng g− 1 dw (Oreochromis mossambicus).
The most prominent herbicides detected included the two phenoxy-acid herbicides, MCPA (17.6 ±
12 ng g− 1) and 2,4-D (28.9 ± 16 ng g− 1), along with acetochlor (15.4 ± 5.8 ng g− 1), atrazine (12.7 ±
7.1 ng g− 1) and terbuthylazine (12.4 ± 12 ng g− 1 ).

24. SEDIMENTATION
The process of particles settling to the bottom of a body of
water is called sedimentation.
• Loss of important or sensitive habitats
• Changes in nutrient cycling patterns
• Changes in water circulation
• Increase in turbidity
• Loss of submerged vegetation
• Changes in fish migration
• Decrease in fishery resources
• Coast line alterations
The wetlands of Nepal and Ramsar sites which are highly rich in biodiversity are facing threats
which mostly include sedimentation, agricultural runoff from fields, pesticide contamination etc.
(IUCN Nepal, 2004). (Shrestha et al., 2020)

25. POTENTIAL IMPACT ON FISHERIES
Toxicity & anoxia causes mass mortality of fishes.
Even though fishes can migrate from hypoxic zones , the bottom dwelling bivalves, coastal crabs,worms
cannot.
Reduce light availability for coral and seagrass photosynthesis due to increased turbidity
Nutrient pollution leads to algal blooms, which decimate fish and wildlife populations

26. CONTD.
According to the United Nations, the
biodiversity of the Arabic Gulf’s coastal sea-
grass and coral is threatened by agricultural
runoff. (Alzahrani and Alqasmi, 2013)
Smother coral reef organisms due to the
settling of suspended sediment.
(De'ath and Fabricius, 2010) inference that
minimizing agricultural runoff should reduce
macroalgal cover on average by 39% and
increase the species richness of hard corals
and phototrophic octocorals on average by
16% and 33%, respectively.

27. BIODIVERSITY LOSSES IN CHILKA LAKE.
Apart from about 1100 sq. km. water-spread area of the lake, rest of the drainage basin of Chilika
comprises 2,325 sq. km. of agricultural land.
Pollution and eutrophication in the lake have been increasing because of growing chemical based
industries in the catchment areas, agricultural intensification in Chilika basin and sprawling of
prawn culture ponds especially since mid 1980s.
Presence of fatalistic heavy metals like mercury, lead, copper, chromium and nickel in the lake
have been reported. The net effect of eutrophication is the excessive weed growth (because of
high influx of organic rich silt and sedimentation over the years and progressive decline in
salinity).
Biodiversity losses in Chilika lake are tremendous. The number of fish species seem to have come
down from 126 in 1920s to around 69 in 1988. Chilika, once used to be a prawn abundant lake on
which variety of other fishes used to prey has become prawn scarcity lake, which gets reflected
through excessive decline in both fish and prawn landings.

28. CONTD.
Weed spread is increasing at a rate of 14.3 sq. kms per year since 1973. The lake area infested
with weed growth has come to alarming proportions of around 52 percent in 1996.
The effects of weed growth is felt not only on aquaculture but more so in terms of drastically
reducing these valued visitors particularly noticed near the Nalabana bird sanctuary in the parts
of the lake.
It result in decline in quantity and variety of fishes on which these birds used to prey.
This have resulted in substantial decline in eco-tourism and international tourists, which used to
contribute greatly towards improvement in economic conditions of the people around Chilika
lake.

29. The Himalayan region is experiencing a great tectonic movement ,so the land elevation of the all
river system coming from the Himalaya is diversified and thus the river erosion, carrying and
depositional capacity also may varied. As a result of it, Delta formation may affect.
Variation in elevation of coastline, continental shelf and estuarine is created huge magnitudes of
surface runoff changes. By which huge amount of agricultural runoff, industrial runoff, municipal
runoff are accumulate with this river water and deposited in lower basin and coastal region of
north-east India. Due to dynamic land elevation, all the pollutants are mixing up with the
sediments.
Sediment pollutants are creating adverse effect on coastal environment as well as coastal fisheries.
These pollutants are came from vast industrial belt of Odisha state and huge agricultural land of
West Bengal.

30. Many tidal rivers also caring these agricultural sediment pollutants through runoff. These rivers
are Matla, Gosaba, Jalangi, Ichamati, Bidyadhari etc. These pollutants make the coastal
environment so vulnerable for living elements especially fishes.
CONSEQUENCES TO FISHERIES:
1. Fish species are wiped out.
2. Fishes are affected by various diseases due to heavy wastage metal.
3. Amount of fishes is fluctuating day by day.
4. Many ornamental fish species are now endangered.

31.  An attempt has been made to study cultural eutrophication by nutrients sourced from agricultural and
industrial waste affecting phytoplankton abundance and composition in a tropical River Hooghly at the land–
ocean boundary of Sunderbans, NE Coast of Bay of Bengal, India.

32. Certain metals and pesticides are toxic to the salmon nervous system, thereby disrupting feeding and
predator avoidance.
Pesticides suppress the immune system, rendering salmon more vulnerable to pathogens that cause
lethal diseases.
Depress growth rate of juvenile salmon, which can affect their survival
Affect the survival and development of salmon and steelhead eggs
Dissolved copper specifically impairs salmon and steelhead’s ability to detect odors.
Copper can impede predator detection and avoidance, social interaction, prey detection, orientation,
and homing, thereby affecting their survival, distribution, and reproductive success.

33. CONTROL MEASURES
Adoption of BMP’s in agricultural operations to
minimize the sediment load & dissolved
chemicals in runoff.
Maintain good soil tilt & healthy vegetation-
will minimize runoff by increasing infiltration
Terracing, contour plowing, & use of vegetated
water ways to convey runoff- will slow down
water flow from the field.
 Construction of farm ponds to receive run off-
will prevent the flow to other areas & to the
coast.

34. CONTD.
Soil testing should be done occasionally to
find out the nutrient status – and accordingly
formulate the use of fertilizers
Riparian Forest Buffer Systems
• They are the stream side ecosystems that can
be managed to reduce the non point sources
of pollution as it leaves the field and reaches
the stream on the way to the coast.
• Seemed to be excellent nutrient and
herbicide sinks that reduces the nutrient
discharge from the surrounding farming
systems.

35. CONTD.
 Implementing Conservation Tillage: Minimize
Tillage can help reduce erosion, runoff and soil
compaction, which helps reduce the chances of
nutrients reaching waterways.
 Minimize the use of agricultural chemicals by
programs such as “Integrated Pest Management”.
 Adoption of proper waste water management
strategies in live stock farms & Control Livestock
Access to Waterways.
 Education, training, awareness of water quality
impacts by agricultural runoff & the need of
conservation of coastal zone should be increased
through education and extension.

36. REFERENCES
Alzahrani, D. and Alqasmi, H., 2013. Protecting the biodiversity of the Arabic Gulf's coastal waters from agricultural and
industrial runoff case Study-Saudi Arabia. International Journal of Social Science and Humanity, 3(1), pp.62-65.
https://www.buschsystems.com/resource-center/knowledgeBase/glossary/what-is-agricultural-runoff
Mateo-Sagasta, J., Zadeh, S.M., Turral, H. and Burke, J., 2017. Water pollution from agriculture: a global review. Executive
summary.
Ridd, P.V., Orpin, A.R., Stieglitz, T.C. and Brunskill, G.J., 2011. Will reducing agricultural runoff drive recovery of coral
biodiversity and macroalgae cover on the Great Barrier Reef?. Ecological Applications, 21(8), pp.3332-3335.
Sechrest, W.W. and Brooks, T.M., 2002. Biodiversity-Threats. ENCICLOPEDIA OF LIFE SCIENCES.
Shrestha, B., Shrestha, S., Shrestha, A. and Khadka, U.R., 2020. Ramsar sites in Nepal: Conservation, present scenario,
biodiversity value and threats. Journal of Wetlands Ecology, 15.
Tyohemba, R.L., Pillay, L. and Humphries, M.S., 2021. Bioaccumulation of current-use herbicides in fish from a global
biodiversity hotspot: Lake St Lucia, South Africa. Chemosphere, 284, p.131407.

37. REFERENCES
USEPA, 2005. Protecting water quality from agricultural runoff.
Wiens, J.H., 1980. Agricultural runoff and water pollution. Canadian Water Resources Journal, 5(3), pp.78-89.
Xia, Y., Zhang, M., Tsang, D.C., Geng, N., Lu, D., Zhu, L., Igalavithana, A.D., Dissanayake, P.D., Rinklebe, J., Yang, X. and Ok, Y.S.,
2020. Recent advances in control technologies for non-point source pollution with nitrogen and phosphorous from
agricultural runoff: current practices and future prospects. Applied Biological Chemistry, 63(1), pp.1-13.
Zhongming, Z., Linong, L., Xiaona, Y., Wangqiang, Z. and Wei, L., 2021. The Challenge of Feeding the World Sustainably:
Summary of the US-UK Scientific Forum on Sustainable Agriculture.

38. THANK YOU !