Now, as we have finished the exposition of the main investigation lines that have been historically developed on the relationship between the environment and the population, referring to both the developed and the developing countries, it is time to briefly sum up its general features in order to find possible omissions and to point out the possible future investigation lines.

As it has been said throughout our exposition, and in accordance with some authors’ statements presented above all in theoretical essays, or as conclusions taken from a collective word, or conferences collections, the main conclusions on the population-environment relationship that we consider important to be mentioned are the following ones:

• The demographic perspective is being reduced, in most of the cases to the absolute population growth, without paying attention to the variables (fertility, mortality, migrations, sex/age structure) that determine it and to their connection with the environment.
• This fact is partly due to the complexity of finding the role of each demographic variable. However, the main reason is that a great amount of the consulted studies were made by external researchers from other knowledge areas, such as social sciences, i.e., the sociology, economy or politics, not from the demography area.
• The interrelationship between the population and the environment cannot be understood without studying the intermediate variables (mainly the economic activities, apart from other factors as the consumption models and the mobility needs) which determine the impacts magnitude and expansion.
• The effects of the demographic pressure on the environment depend on the territorial variation, according to the social, cultural, demographic, economic and natural conditions of each region. Therefore, the generalisations in the interrelationships between the population, the technology, the lifestyle and the environment are difficult to be made, because of the development inequality.
• Accordingly, the poverty, the gender equity, the levels of consumption per capita, the resources accessibility, the technology, etc, are specially important factors.
• The resources are finite, but abundant, and often replaceable with other sources. The current problem is not the exhaustion, but the abuse.
• The overpopulation is not an absolute estate; it is relative to the expectations, the lifestyles, the technologies, the artificially created needs and the environment.
• The demographic pressure, the overconsumption, the soil degradation, the deforestation, the climate change, the biodiversity loss, the water contamination have imposed the establishment of political and scientific measures in order to maximally reduce the environmental impact.

According to the above mentioned, and according to some authors, we think that the future investigation lines on this topic should also consider:

• The specification and the concretion of the conceptual structure and the extension of the concepts, within the study of the relationship with the environment, through the incorporation of other variables a part from the population growth, such as the age/sex structure, the space distribution, the nuptiality, the migrations and the incorporation of the people perception on the environment studies.
• Differentiating the analysis scale and admitting the need of micro-scale studies. The study of the population-environment relationships varies depending on the studied geographical fields: the Earth, the regions, the countries, the communities, the houses, etc
• A wider proliferation of the micro-scale studies should allow a vaster knowledge of the interrelationships, since they depend on very specific socioeconomic, geographical and environmental determinants. Moreover, these types of study are those that should allow the implementation of efficient policies, by following the known slogan ‘think globally, act locally’.
• The achievement of a greater causal and temporal analysis and the need of complementing the transversal vision or cross-section of many studies with another vision which would have a bigger consideration of the temporal mechanisms and the cause and effect relationships.

The research on the compatibility of the future data collection, as there is a high potential in the use of the information sources available for analysing the relationships between the population and the environment