Twin Priorities of Sustainable Development Goals
As the target date of the Millennium Development Goals (MDGs) is approaching, the international community agreed at the Rio+20 Earth Summit to start a process of establishing an updated set of sustainable development goals (SDGs) by 2015. The key difference between SDGs and MDGs is self-evident in their names: SDGs are not merely about development but clearly intended to promote sustainable development, which expresses a particular substantive concern. Whereas eradicating poverty was the overall objective of MDGs, environmental protection is expected to constitute an integral part of the development process under the post-2015 sustainable development agenda. In that sense, it has been argued that “the protection of Earth’s life-support system and poverty reduction must be the twin priorities for SDGs”. Although long overdue, this is a step in the right direction for global sustainability.
However, the twin priorities pose a unique challenge to the implementation of SDGs as the two may conflict. One of the key challenges to achieving SDGs is, therefore, going to be how to reconcile the twin priorities. Striking a tenuous balance between the competing demands of development and environmental protection has always been at the crux of the sustainable development challenge. Even if States manage to come up with several ‘integrated’ goals such as “[e]nsure sustainable food and nutrition security worldwide”, the system of goals, targets, and indicators will still contain inherent contradictions in itself. For example, increased fertilizer use may feed more people, but only with environmental consequences. As a set of goals, SDGs per se will provide little guidance as to where the balance lies between food security and environmental sustainability.
The ultimate success of SDGs in achieving sustainable development will largely depend on the ability of our institutions, such as international law, to reconcile the twin priorities in a principled manner, resolve any conflicts, and avoid “a state of normative anarchy”.
Sustainable Development as the Principle of Reconciliation
When implementing SDGs, it might become necessary to have recourse to what MDGs referred to as the “principles of sustainable development” (Target 7A) and, in particular, the concept of sustainable development that underlies these principles. Although the international legal status of sustainable development remains a subject of debate, the concept has already influenced the outcome of several judicial decisions of various international courts and tribunals, and it is increasingly understood as a general principle of international law.
In the Gabčíkovo-Nagymaros case, the International Court of Justice invoked sustainable development as an international legal concept that refers to the “need to reconcile economic development with protection of the environment”. The Vice-President Weeramantry took it a step further in his Separate Opinion and made a compelling case that sustainable development is “more than a mere concept” and that it is “a principle with normative value”. For him the principle of sustainable development is “a part of modern international law by reason not only of its inescapable logical necessity, but also by reason of its wide and general acceptance by the global community”. The Treaty of European Union, as amended in 1997, for example, includes a reference to “the principle of sustainable development” in its Preamble.
In the Shrimp/Turtle case, the Appellate Body of the World Trade Organization noted that the Preamble to the organization’s foundation agreement explicitly acknowledges “the objective of sustainable development”, and characterized it as a concept having practical legal consequences. In the Iron Rhine case, the Permanent Court of Arbitration recognized the duty to ensure that development does not significantly harm the environment as “a principle of general international law”. In the Pulp Mills case brought before the International Court of Justice, Judge Cançado Trindade emphasized in his Separate Opinion that sustainable development has turned out to be “a general principle of International Environmental Law”.
It can be observed that sustainable development has been gaining legal currency as a de facto “principle of reconciliation” in international law. If sustainable development is not already a principle of international law, one may reasonably expect it to become one in the foreseeable future. And this has significant implications for the establishment and implementation of SDGs. As mentioned above, SDGs will support both development and environmental protection without an inbuilt mechanism for their integration, and the principle of sustainable development will be necessary for resolving normative conflicts. So, how does the principle of sustainable development balance the needs of development with the protection of the environment?
As a principle, sustainable development recognizes both the right to development and the right to environmental protection as equally established rights under international law. Because they are equal, the “right [to development] does not exist in the absolute sense, but is relative always to its tolerance by the environment”. In other words, development cannot be pursued to such a point as to result in significant or irreversible damage to the environment within which it is to occur. Therefore, “development can only be prosecuted in harmony with the reasonable demands of environmental protection”. Although the principle does not confer automatic priority to the pursuit of purely environmental values, it signifies that, in sustainable development, ‘sustainable’ conditions ‘development’, not vice versa.
This legal obligation to develop sustainably does not require ecocentric reasoning, but anthropocentric reasoning suffices. This is because, as Judge Weeramantry argued, the protection of the environment is “a sine qua non for numerous human rights such as the right to health and the right to life itself”. This dictum is becoming ever more apparent as environmental science advances. Compelling scientific evidence now indicates that many Earth’s subsystems (e.g., the climate) react in a nonlinear way, and are particularly sensitive around threshold levels of certain control variables such as the atmospheric carbon dioxide concentration. Transgressing these so-called planetary boundaries will likely translate into irreversible and abrupt environmental change, leading to a state less conducive to human development. Therefore, for any kind of long-term human development, we must respect certain biophysical preconditions.
International Law as a Normative Context for the Sustainable Development Goals
As discussed, international case law on sustainable development started to emerge since 1997. Today’s international legal landscape in which post-2015 SDGs are being debated is substantially different from that of the Millennium Summit where MDGs were adopted. In 2015, SDGs will not enter into a normative vacuum, but a body of “international law in the field of sustainable development”, which has arguably existed from the time of the Rio Declaration. Sustainable development is a well-established concept in international law, widely found in many multilateral treaties, international declarations, and the practice of States and international organizations. More importantly, the concept has been invoked by numerous international courts and tribunals and influenced their judgments in effect as the principle of reconciliation that recognizes both development and environmental protection as equally established rights under international law.
This paper has tried to highlight the importance of recognizing this normative context in which SDGs will operate. International sustainable development law has a potentially important governance function to play for effective implementation of SDGs. For its relevance and necessity to SDGs, it would be a mistake for policy makers and stakeholders to overlook the emerging principle of sustainable development when negotiating and implementing SDGs. Creating a mutually supportive relationship between SDGs and international law will be critical for effective implementation of the post-2015 development agenda.
 See, for example, Principle 4, Rio Declaration on Environment and Development, UN Conference on Environment and Development, Rio de Janeiro (Brazil), 3–14 June 1992, UN Doc. A/CONF.151/26/Rev.1 (Vol. I), 14 June 1992.
 D. Griggs, M. Stafford-Smith, O. Gaffney, J. Rockström, M.C. Öhman, P. Shyamsundar, W. Steffen, G. Glaser, N. Kanie and I. Noble, “Sustainable Development Goals for People and Planet,” Nature 495, no. 7441 (20 March 2013): 305–307, page 305.
 Report of the Appellate Body, World Trade Organization, “United States – Import Prohibition of Certain Shrimp and Shrimp Products,” WT/DS58/AB/R (12 October 1998). See also P. Sands, “International Courts and the Application of the Concept of “Sustainable Development”,” Max Planck Yearbook of United Nations Law 3: 389–405.
 See, for example, C. Voigt, Sustainable Development as a Principle of International Law: Resolving Conflicts between Climate Measures and WTO Law (Leiden: Martinus Nijhoff Publishers, Leiden, 2009).
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