Impact of fertilizers on freshwater ecosystems
By Maggie
Lehar
Pollution by
nutrients from agriculture causes many problems in the environment. In fact,
“agricultural practices are ranked as the most important factor for rivers and
lakes”(Puckett 408). One of the main sources of the problems that arise from
agriculture is fertilizer pollution. While fertilizers can be used to
strengthen soil’s productivity and be extremely useful for agriculture when
soil is insufficient in phosphate, potassium, nitrogen, or other nutrients, it
can also have many extremely detrimental effects to the surrounding ecosystems.
Too much fertilizer can effect the environment in many different ways, and some
of these effects are extremely harmful to the environment. When fertilizer is
used in excess and individual’s use of fertilizer is not in line with the codes
of good agricultural practice, the excess fertilizer is washed away by the rain
and runs off into steams, rivers, and other bodies of water. This overuse of
fertilizer is extremely common, and “studies have estimated that famers apply
24%-38% more fertilizers than crops require because of uncertainties regarding
the amount needed”(Puckett 408-409). Because fertilizer contains naturally
occurring elements that support plant growth, fertilizer runoff disturbs the
natural nutrient balance and cycles that exist in ecosystems, which are
extremely complex and delicate. This change in the balance of nutrients can
cause algal blooms which are harmful have negative effects in bodies of
freshwater.
Before
one can fully understand the impact that fertilizer pollution has on different ecosystems,
it is important to have a better understanding of fertilizer itself, and why
fertilizer is even necessary. As man transitioned from being nomadic to
creating permanent settlement, he was forced to change methods of obtaining
food. Instead of relying solely on hunting, fishing, and gathering, people
began to rely mainly on agriculture and
animal breeding for their main methods of obtaining food. This marked a very important
change in the history of humans for many different reasons. For the first time
in history, humans had to produce the vast majority of their food themselves
instead of finding it elsewhere by either hunting, fishing, or gathering. The
emergence of agriculture led to people having a relatively high and stabile
food production, and this relatively high and stable food source caused an
accelerated population growth. This growth in population led, in turn, to an
increase of food demand to support the growing population. And while some
regions benefited from natural fertilization like Egypt where the floods of the
river Nile renewed the fertility of the soil almost each year, other
civilizations did not have such advantages. Many civilizations were in regions
where the climate was not very conducive to agriculture. Unfavorable weather
conditions led to famines, and together with wars reduced the population. The
issue of maintaining or improving the fertility of soil in regions where the
soil’s fertility was not naturally renewed became more and more important as the
population continued to grow. The availability of food was a major limiting
factor on how large a population could grow, and the fertility of soil was the
main limiting factor on the amount of food that could be produced. That is why
the discovery that all the nutrients plants removed from the soil could be
restored in mineral form in 1847 by the German agricultural chemist Justus von
Liebig, was the basis for far reaching changes. A few hundred years later and
fertilizer usage was very common as well as comprehensive. This led to an
increase in the amount of food that was able to be produced which in turn led
to a sharp increase in population growth. Because of this, fertilizer use has
had a drastic effect on the course of human history.
This increase in fertilizer use, food
production levels, and population growth continued into the 20th
century. The global use of fertilizers increased from 14 million tons per year
to over 146 million tons per year just between the year 1950 and the year1989
alone. During the same period of time, the grain production in the world nearly
tripled. The world population also grew 2.5 billion in 1950 to about 5.5
billion in about 45 years. Ongoing population grow, growing water scarcity
possible
climatic changes, and declining soil fertility all make it so it would be near
impossible to produce enough food for today’s population without the use of
fertilizer. “Synthetic fertilizer is credited for allowing humanity to increase
food production to keep pace with the twentieth-century population increases.
Over half of all fertilizer employed in human history was used in the last 20
years of the twentieth century. The amount of synthetic fertilizer now used
equals the amount of naturally available reactive nitrogen, and its use
continues to grow”(Hill 273). Many people may wonder upon hearing how dependent we as humans have become
on fertilizers what exactly it is about the chemical make up of fertilizers that
makes them so advantageous. This is because
fertilizers are composed of a number of different chemical elements that are
necessary for a plant to grow and thrive. This includes nitrogen, phosphorus,
potassium. Nitrogen, phosphorous, and potassium are 3 of the most common
macronutrients that plants need to survive. Nitrogen, phosphorus and potassium
are important because they are necessary for the basic building blocks of life.
For example, every amino acid contains nitrogen, every molecule making up every
cell's membrane contains phosphorous and so does every molecule of ATP. Also
potassium makes up 1 percent to 2 percent of the weight of any plant and, as an
ion in cells, is essential to the metabolism of that cell. Because of this, it
is obvious that without nitrogen, phosphorus, and potassium, the plant simply
cannot grow because it cannot make the pieces it needs. If any of the
macronutrients are missing or hard to obtain from the soil, this will limit the
growth rate for the plant. If the plant is unable to obtain any of the three
nutrients, it will be unable to grow properly. In nature, the nitrogen,
phosphorous and potassium often come from the decay of plants that have died.
This is a part of the nutrient cycling that occurs in each ecosystem. However,
in cases where plants are grown repeatedly over time without allowing the soil
and opportunity to regain these vital nutrients, the soil becomes depleted of
these nutrients. This is what occurs in agriculture, when a farmer plants crops
season after season in the same field. Eventually the soil will become so
depleted of nutrients that it will become infertile and plants will no longer
be able to grow there. After a few years, when a farmer plants his crops in his
field, they will not grow because they will not have access to the basic
nutrients that they need to grow and thrive because those nutrients are not
available in the soil. This is where the use of fertilizer comes in. All that
is needed in order to make the soil fertile again is the elements that the
plants need in readily available forms. Fertilizer does just that; it supplies
plants with nitrogen, phosphorus, and potassium, along with some fertilizers
supplying other nutrients as well. Nitrogen, phosphorus, and potassium
availability is the main limit to the growth of plants. Even more than just
supplying nitrogen, phosphorus, and potassium, fertilizer supplies these vital
nutrients in readily available forms so that plants can easily obtain and use
them.
While it may seems counter
intuitive that an increase of nutrients which are vital in order to sustain
life could have negative effects on organisms, an overabundance of these
nutrients disrupt a delicate balance that exists in aquatic ecosystems. All
minerals and nutrients cycle through soils and living systems. The amount
of these nutrients available to plants and animals is extremely important to an
ecosystem, and there is a delicate balance of nutrients constantly cycling
through each given ecosystem. There are different cycles for each nutrient, and
different nutrients have different ways in which they are cycled through
ecosystems. These cycles are often complex and have many different factors that
contribute to them. These nutrients that are
being cycled though a given ecosystem are limiting factors, which means the
amount of these nutrients available determines the size of the population that
can be supported. For example, if there is only so much nitrogen available in a
pond, only a finite number of organisms will be able to survive off that amount
of nitrogen and the rest will die. When there is a sharp increase of nutrients
that were previously limiting factors in an ecosystem, it creates a large
increase in the rate of population growth of organisms. Using the previous
example, if there is suddenly a drastic increase in the amount of nitrogen in
the pond, many more organisms will be able to survive. When a lake of pond is
polluted by the run off of nutrient rich fertilizers, it is usually followed by
a large growth in the population of algae, sometimes referred to as an algal
bloom. “Just as on land, these nutrients
stimulate plant growth in water…nutrients stimulate phytoplankton (algae)
growth in water, sometimes enough to cause an algal bloom”(Hill 245). This
large population of algae eventually dies, and the dying algae in turn feeds bacteria. Because there is a much larger
population of dead algae, there is much more food available for bacteria, and
the bacteria population grows. This larger population of bacteria consumes so
much dissolved oxygen that it causes anoxic conditions in which fish and plants
cannot survive. Without the fish and plants, the nutrient cycles are completely
disrupted and the ecosystem is destroyed completely. These effects occur in
almost all aquatic ecosystems, but the effects are most easily observed in
ponds or lakes where there is no outflow of nutrients. Many rivers and streams
may lead into lakes or ponds, bringing nutrients and pollution, but there is no
outflow, which means once a nutrient is delivered to the ecosystem, it will
remain there.
The important
difference (between lakes and rivers) is, of course, that the residence time
indicating the mean period a water molecule and other substances remain in the
water body. Therefore, rivers damaged by the pollution can be cured much faster
than lakes which keep the substance longer…(in a lake) the sub- stances in the
water are trapped and even small amounts given constantly over long periods
will lead to high concentrations. (Kremser 85)
This means that ponds and lakes are especially vulnerable to fertilizer
pollution, because even small amounts of fertilizer runoff can accumulate
overtime and have extremely negative effects on ecosystems.
It may seem like there is
no solution to this problem. We cannot completely stop using fertilizer because
we simply would not be able to grow the amount of food necessary to support our
current population without using fertilizer, however we know that fertilizer is
harming the environment in many serious ways. In other words, there is no
alternative to fertilization and no alternative to protecting the environment
and the water bodies. In fact the problem is even more serious because
fertilizer use is expected to increase in coming years. “Fertilizer use is
projected to continue to increase, especially in Asian, African, and South
American countries, which now use relatively little”(Hill 275). This may seem
like humans are in a dilemma with no solution and we are simply left with
choosing the lesser of two evils. However, although it is a very concerning
problem, there are various measures we can take to solve the problem without
compromising our food source or the health of the environment. In fact we don’t
really have a choice in the matter of what to do. We must continue to use fertilizers
in order to produce enough food, but we also must reduce the effects of
fertilizer on the environment.
Since stabile
food supply in future is essential, mineral fertilization has to be continued.
But one should try to minimize the adverse impact to the environment - other-
wise the basis of our life will be destroyed. (Kremser 87)
As is the case with many problems,
the first step to solving the problem is acknowledging that there is a problem.
This has proved difficult for humans to do in terms of the problem of
fertilizer pollution. Despite agricultural activities always having been a
burden to nature, it took centuries to acknowledge this truth. Agriculture and
fertilization became a problem in the second half of the 20th Century at least
in Europe and in America in line with strong increase of food production,
fertilization and population growth. Just recently it has been officially
recognized as a problem in Europe and worldwide and this can be considered as
the first step for dealing with the problem properly. We now know more about
the harm that fertilizer pollution causes, and with this greater understanding
we are better equipped to handle the problem. “So far there are two general
ways that scientists have suggested approaching the problem. There is the
option of improving the efficiency of fertilization or there is the option of taking
measures for protecting the water bodies. The best solution is probably one
with incorporates both or these solutions.
Improving the efficiency of fertilizers could
be achieved in many ways, but whatever way the efficiency of fertilizers is
improved, it is necessary that changes are made from the current methods. “To
sustain the future world population more fertilizers are required, which may
become an environmental hazard, unless adequate technical and socio-economic
measures are taken”(Ayoub). For example, the process of fertilizer coating is a
way of improving fertilizer efficiency which has already been put into use by
some fertilizer brands. Coating is a process in which a variety of coatings have been applied to fertilizer particles to
control their solubility in soil and thereby controlling the rate of nutrient
release. Granulation of the fertilizers is also effective, in which more
precise amounts of various nutrients can be used instead of large,
overestimated amounts of many nutrients are used. This is similar to the method
of precision agriculture. These solutions are not only effective in terms of
reducing the harmful effects of fertilizer as a pollutant, but they are also
cost effective. This means that they are extremely viable and realistic
solutions to the problem at hand. It is extremely important that any solution
to the problem be cost effective because if any solution is too expensive, then
it would be unlikely that any farmer would utilize that solution.
Changing
farming methods to reduce agricultural runoff can present major challenges to
farmers. They need to be willing to educate themselves on methods to reduce runoff.
Taking action can mean significant changes in farming methods, and require more
time, and often additional costs. Providing incentives or assistance can make a
difference. (Hill 269)
Providing incentives or assistance to farmers could be a job of the local,
state, or national government, considering the risks of farmers using poor and
harmful fertilizer distribution techniques and methods.
While many methods of reducing the harmful
effects of fertilizer as a pollutant are effective, they are not enough on their
own to solve the problem of fertilizer pollution. As previously mentioned,
especially in lakes and ponds, fertilizer pollution can accumulate over time.
This means that the measures to increase the efficiency of fertilizer could
slow the effects of fertilizer pollution, but they cannot completely stop them.
This means that measures for protecting the water bodies are also necessary in
order to have a more complete solution for the problem of fertilizer pollution.
These measures are usually more complex than the measures taken to improve the
efficiency of fertilizers. They also usually require some involvement from
government on either a local, state, or national level. According to Olga
Hayes, a member or the Manchester Conservation Commission, the best-case
scenario in terms of protecting and body of water is a mix of legislation on
the local, state, and national level. This combination of local, state, and
national legislature for protecting bodies of water is ideal because it ensures
all bodies of water are protected, but also allows for laws which are adapted
to the specific states or towns. The good news is that in places where efforts
have been taken to reduce the effects of fertilizer pollution, there has been a
drastic decrease in nutrient pollution. An example of this is in Danish lakes.
Attempts have
been made to reduce nutrient loading in Danish lakes by intervening at the
source level and improving the retention capacity of catchment areas. The
former measures include phosphorus stripping and nitrogen removal at sewage
works, increased use of phosphate-free detergents and regulations concerning
animal fertilizer storage capacity, fertilizer application practices, and
fertilization of plants and green covers in winter…These measures have resulted
in 73% reeducation of total phosphorus. (Ansari 164).
This is especially significant in regards to the pollution of bodies of
freshwater because phosphorus is the nutrient that is mainly responsible for
the harmful effects on bodies of fresh water by fertilizer pollution. “Phosphorus
is more often a limiting nutrient for phytoplankton in freshwater bodies while
Nitrogen is often the limiting nutrient in marine water”(Ansari 71). Results
like the ones observed in the Danish lakes show that it is extremely possible
to reduce the amount of the nutrient phosphorus pollution into bodies of
freshwater. Therefore, it is reasonable to assume that if the same measures are
applied, it would also be possible to greatly reduce the amount of the nutrient
nitrogen pollution. However, cooperation between local, state and national
government might not be enough for a long-term solution for fertilizer
pollution. A more permanent solution to the issue of fertilizer pollution might
require international cooperation as well and national, state, and local
cooperation. This is because the pollution of fertilizers from other countries
can and will have harmful effects on not only the fresh bodies of water and
bodies of salt water in that particular country, but also in various different
countries around the world. This means that even if a country has cooperation
between local, state, and national government to regulate and manage the use of
fertilizers, they could still face the harmful effects that fertilizer
pollution has because of the fertilizer pollution of other countries. For this
reason, in the future international cooperation will likely be necessary.
The purpose of agriculture is to guarantee a
secure food supply for the entire world population and this purpose requires
fertilization. However, this does not mean that damaging the environment in the
process of fulfilling the task is acceptable. Preserving the environment is of
the same priority as agriculture and guaranteeing a secure food supply for the
entire world population, or at least it should be.
Fertilization and the
pollution caused by the runoff of fertilization causes few direct effects on
the environment, but it does cause many indirect effects that impair
ecosystems. Many of these effects are long-term effects that are difficult to
reverse, especially in the case of rivers and streams. Fertilization and the
pollution caused by the runoff of fertilization disrupts the delicate balance
of ecosystems and ruins the many complex nutrient cycles that exist within the
ecosystems. The eutrophication of rivers, lakes and seas is considered as one
of the important environmental problems that we are facing today, and
fertilization plays a major role in this problem.
Adopting and implementing
tailored programs for reducing the nutrient input of fertilizers can eventually
be a successful way of reducing the extremely harmful and drastic effects that
fertilizers can have on the environment, and this has been proven by multiple
studies, such as the effects observed in the Danish lakes when efforts were
made to reduce fertilizer pollution.
Because the effects of fertilizer
pollution are not immediate or short term, some people may be under the
impression that the nutrient pollution is not really a threat to the
ecosystems. This impression, however, is incorrect and extremely dangerous.
Fertilizer pollution sets off a chain reaction which leads to eventual
destruction of ecosystems.
Consequently there is the demand to preserve the
ecosystems effected by fertilizer run off. It is a problem that needs immediate
action in order to prevent further damage including the alteration and
destruction of habitats and ecosystems
, widespread and increased
eutrophication
, and changes in sediment flow. Many of these harmful effects
are much easier to prevent than they are to reverse, which is why it is
extremely important that we take immediate action to reduce the effects of
fertilizer pollution. The available knowledge we have in regards to the effects
of fertilizer pollution as well as the general knowledge we have of how ecosystems
work allows us to understand and think of solutions that can solve or at least decrease
the effects of fertilizer pollution. The decisive question in regards to
fertilizer pollution is however, whether political powers and financial powers worldwide
do support such a goal since protection of the environment seems to require
involvement and participation from such powers. Cooperation on a local, state,
and national level might not be enough to completely solve the problem of
fertilizer pollution, and international cooperation might be necessary in order
to permanently solve the issue.
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