How does the water cycle affect ecosystem dynamics?

1. What is the
role of age
structure in
population
dynamics?
The age structure of the population is one of the key categories in demographic studies. On
the one hand, it serves as a basic tool for studying the labor potential of any socio-economic
object, and on the other hand, it has a direct impact on the process of reproduction of the
population. It is known that the number of deaths is directly related to the age proportions
of the population, and the number of women of reproductive age in the population, along
with other factors, affects the possible number of births. At the same time, the age structure
is the result of the evolution of demographic processes in the past and at the same time an
independent component of future demographic development. Its changes as an element of
shifts in population reproduction make it possible to comprehend the internal patterns of
population growth

2. • Global trends in the development of the age structure of the
population are well studied. There is no doubt about the
progressive process of his aging. Over the past decades, the
proportion of young people in the world's population has been
steadily decreasing and, on the contrary, the proportion of the
elderly has been growing.2 Moreover, the overall pace of this
global process is largely set by the economically most developed
countries, the vast majority of which have long since crossed the
threshold of demographic old age. According to the criteria
developed by UN experts, the population is considered "old" when
the proportion of people aged 65 years and older exceeds 7% in its
structure, and according to the scale of the famous French
demographer J. God-Garnier, clarified by E. Rosset, if the
proportion of people aged 60 years and older is more than 12% of
the population3. Already in the early 1970s, Japan, the United
States, Great Britain, France and a number of other, primarily
European, states were among the "old nations". To date, the
proportion of people over 65 years of age in the age structure of
the population of these countries has become even greater. In the
USA it reached 12.3%, in the UK and France it exceeded 16%, in
Germany it reached 18%, and in Japan it was almost 20%.4

3. How does the
water cycle
affect
ecosystem
dynamics?
• Of all the cyclic processes occurring
in nature, the most widely known is
the hydrological cycle, or water
cycle. It consists of three separate
processes: - evaporation of water
(from the surface of lakes, ponds,
streams, swamps, rivers and
oceans); - condensation of vapors; -
precipitation and its runoff. In
addition to the evaporation of water
from the surface, water is released
by plants, as well as physiologically
(transpiration). However, more
water evaporates from the surface
of the oceans than returns back in
the form of rains.

4. • On land, the opposite situation develops: here the amount of
water evaporated from the surface of soil, plants, reservoirs is
less than the amount of precipitation falling in the form of
rain (the exception is deserts, where evaporation prevails
over precipitation). The balance between precipitation and
evaporation is achieved as a result of water runoff from land
to the oceans in the form of rivers, streams, groundwater.
Figure 1.11 shows the human impact on the hydrological
cycle. Human economic activity strongly influences the water
cycle in nature. This influence can be purposeful and
accidental. For example, in industrial areas, the amount of
precipitation increases, the reason for this is the abundance
of tiny particles of mineral substances that accelerate the
condensation of water vapor. As another example, we will
give an increase in water runoff after the destruction of
vegetation cover, which to a certain extent captures and
retains water penetrating into the soil.

5. What is the role of the biosphere
in providing ecosystem services,
such as carbon sequestration and
water purification?

6. • Supporting services, such as primary and secondary
production, and biodiversity, a resource that is
increasingly recognised to sustain many of the goods
and services that humans enjoy from ecosystems.
These provide a basis for three higher-level categories
of services.
• Provisioning services, such as products i.e., food
(including game, roots, seeds, nuts and other fruit,
spices, fodder), fibre (including wood, textiles) and
medicinal and cosmetic products
• Regulating services, which are of paramount importance
for human society such as carbon sequestration, climate
and water regulation, protection from natural hazards
such as floods, avalanches or rock-fall, water and air
purification, and disease and pest regulation.
• Cultural services, which satisfy human spiritual and
aesthetic appreciation of ecosystems and their
components.