Such an understanding will help in the assessment process to quantify the impact as accurately as possible. Complex interactions, particularly in the case of certain indirect or cumulative impacts, may give rise to nonlinear responses which are often difficult to understand and therefore their significance is difficult to assess.
It is therefor understood that indirect or cumulative impacts are more complex than the direct impacts. Currently the impact assessments are limited to direct impacts. However, the ultimate objective of an EIA is to achieve sustainable development. The development process shall invariably cause some residual impacts even after implementing an EMP effectively.
There is no doubt that environmentalists today are faced with the vital question of - “What is the tolerable level of environmental impact within the sustainable development framework?”, keeping in mind, that it has been recognized that every ecosystem has a threshold for absorbing deterioration and a certain capacity for self regeneration.
Environmental impacts resulting from proposed actions can be grouped into following categories:
- Beneficial or detrimental.
- Naturally reversible or irreversible.
- Repairable via management practices or irreparable.
- Short-term or long-term.
- Temporary or continuous.
- Occurring during construction phase or operational phase.
- Local, regional, national or global.
- Accidental or planned (recognized before hand).
- Direct (primary) or Indirect (secondary).
- Cumulative or single.
The category of impact as stated above and its significance will assist in the decision making process about the developmental activity.
The nature of impacts could fall within three broad classifications i.e., direct, indirect and cumulative, based on the characteristics of impacts. The assessment of direct, indirect and cumulative impacts should not be considered in isolation or considered as separate stages in the EIA.
If one is to do an EIA correctly, the assessment of such impacts should form an integral part of all stages of the EIA. It is not recommended the use of a single method to assess the types of impacts, but it should instead use a practical framework/approach that can be adapted and combined to suit a particular project and the nature of impacts.
Let's look at some of the more critical ones in a bit more detail.
Direct impacts occur through direct interaction of an activity with an environmental, social, or economic component. The oil and gas exploration and productions activities may contaminate the basic environmental media. For example, the discharge of wastewaters would directly impact the water and soil quality in the vicinity and finally the health of the workers.
Indirect impacts on the environment are those which are not a direct result of the project, often produced away from or as a result of a complex impact pathway. The indirect Conceptual Facets of EIA impacts are also known as secondary or even tertiary level impacts.
An example of indirect impact is the decline in water quality due to the discharge of wastewaters and other crude oils into the sea. This may, in turn, lead to a secondary indirect impact on aquatic flora in that water body and may not be any further fishing activities.
Reduction in fishing harvests, affecting the incomes of fishermen is a third level impact. Such impacts are characterized as socio-economic (third level) impacts. The indirect impacts may also include growth-inducing impacts and other effects related to induced changes to the pattern of land use or additional road network, population density or growth rate. In the process, air, water and other natural systems including the ecosystem may also be affected.
Cumulative impact consists of an impact that is created as a result of the combination of the project evaluated in the EIA together with other projects in the same vicinity causing related impacts. These impacts occur when the incremental impact of the project is
combined with the cumulative effects of other past, present and reasonably foreseeable future projects.
The cumulative impacts can be due to induced actions of projects and activities that may occur if the action under assessment is implemented such as growth-inducing impacts and other effects related to induced changes to the pattern of future land use or additional road network, population density or growth rate (e.g. excess growth may be induced in the zone of influence around an offshore and onshore oil and gas industry, and in the process cause additional effects on air, water and other natural ecosystems).
Induced actions may not be officially announced or be a part of any official plan. Increase in workforce and nearby communities contributes to this effect.
They usually have no direct relationship with the action under assessment, and represent the growth-inducing potential of an action. New roads leading from those constructed for a project, and construction of new service facilities are examples of induced actions.