Insight Understanding the Total Portfolio Approach: Sustainable investing and asset allocation

Introduction

Our earlier Understanding the Total Portfolio Approach: A primer set out the distinction between Strategic Asset Allocation (SAA) and the Total Portfolio Approach (TPA). Our subsequent private-markets paper explored what changes when investment opportunities are illiquid, manager-dependent and difficult to compare through traditional asset-class labels. This third paper applies the same framework to sustainable investing. It asks the question: what changes when investors seek to manage financially material sustainability-related risks and to allocate capital to opportunities associated with long-term sustainability themes such as climate transition, resilience and adaptation?

Sustainability began largely as a question of how risks and opportunities should be managed within existing mandates. Increasingly, it is also a question of how capital, risk and impact should be allocated across the whole portfolio. TPA is well suited to that shift because it allows different implementation routes to be compared against a common total-fund objective. However, objectives must be explicit, investments must still be assessed on their financial merits, and real-world sustainability outcomes should not be assumed from portfolio labels or capital allocation alone.

The sustainability allocation problem

Sustainable-investing objectives can often be implemented through multiple asset classes, investment vehicles and financing structures. An investor seeking exposure to climate solutions, transition finance or resilience, for example, may be able to access similar themes through listed equities, fixed income, infrastructure, real estate or private markets. The resulting challenge is not whether sustainability considerations can be incorporated within individual mandates, but how competing implementation routes should be compared, prioritised and allocated when they contribute to similar objectives.

Addressing sustainability-related risks makes this shift especially visible in cases where both the risks and opportunities are inherently cross-cutting asset classes. For climate-related risk examples, physical climate hazards can affect assets, cashflows, insurance costs, supply chains, sovereign balance sheets and regional growth. Transition pathways can influence energy prices, technology adoption, capital expenditure, policy exposure, credit quality and the value of carbon-intensive assets. At the same time, the opportunity set could span across a range of climate-related investments, including mitigation, adaptation and enabling technologies, including listed equities, green, sustainability-linked and transition bonds, private credit, infrastructure, real estate, venture capital, and impact investments.

The challenge is not simply how sustainability considerations are implemented within individual asset classes, but how risks, opportunities and outcomes are assessed, prioritised and allocated across the portfolio as a whole. Sustainability-related risks and opportunities often cut across asset classes, which has encouraged investors to complement asset-class analysis with a more holistic view of how these exposures contribute to overall portfolio objectives. This has broadened the discussion from individual mandates to the portfolio level, where trade-offs, diversification and capital-allocation decisions can be considered in a broader context.

Exhibit 1 illustrates how investor focus has broadened over time from issuer-level analysis toward capital allocation and portfolio construction. The stages are illustrative and may overlap in practice. They are not intended to imply a universal evolution or strict sequencing, as each approach continues to serve a relevant role in sustainable-investing implementation.

What SAA handles well

Climate-related investment practices have largely developed within asset-class structures. In public markets, this has included climate-risk integration, scenario analysis, risk monitoring and stewardship, alongside increasing use of thematic strategies, climate-focused indices, active ETFs (Exchange Traded Funds) and labelled fixed-income instruments. In private markets and real assets, investors have incorporated climate considerations through due diligence and an increasing focus on value creation.

This reflects an implementation model in which sustainability considerations are embedded within existing investment processes rather than managed as a separate allocation. Climate risks and opportunities are assessed alongside traditional investment factors, while sustainability objectives are incorporated through mandates, guidelines, stewardship priorities and reporting frameworks. Asset-class teams retain responsibility for investment decisions, risk management and implementation, providing clear ownership, governance and accountability across the portfolio.

Within this model, accountability is typically assigned through asset-class mandates, with individual teams responsible for investment decisions, risk management and implementation. Governance structures, investment committees and allocation frameworks provide oversight and coordination across the portfolio, helping investors evaluate sustainability-related exposures both within individual mandates and in the context of overall portfolio objectives. As a result, sustainability considerations can be incorporated at both the asset-class and portfolio levels while maintaining clear ownership and accountability.

Case study: IQS as an asset-class implementation example

Invesco Quantitative Strategies (IQS) materials illustrate how sustainability objectives can be embedded within a defined listed-equity allocation. The approach combines safeguards, active ownership, dedicated research, carbon controls, social and green-revenue considerations, exclusions and controversy screening with active portfolio construction. A separate IQS net-zero framework describes a two-step design that first creates a climate-aware market-like portfolio and then adds a factor overlay, aiming to separate climate alignment from return-seeking factor exposure. In an SAA context, this is a useful example of mandate-level discipline: climate improvement is pursued within a defined equity sleeve, with tracking error, sector exposure, factor exposure and attribution monitored together.

The chart illustrates how sustainability-related exposures can be analysed alongside traditional factor exposures within a defined equity mandate. Rather than treating sustainability as a separate allocation decision, the approach incorporates ESG-related risk into the overall portfolio construction process and evaluates its contribution alongside factor risk and diversification effects. This reflects the broader SAA implementation model where sustainability considerations are integrated within asset-class mandates while remaining subject to established portfolio-construction disciplines, risk budgets and accountability structures.

Where cross-asset objectives create friction

Sustainability considerations can be incorporated within asset-class mandates through both risk integration and opportunity identification. As investor objectives have expanded to include transition, resilience and climate solutions, some themes increasingly span public and private markets, fixed income, infrastructure and real estate. This broadens the discussion from individual investments to how related exposures contribute to portfolio objectives and intended outcomes, while remaining anchored in established asset-class expertise, governance and decision-making processes.

As sustainability themes increasingly span asset classes, investors may also consider how related exposures interact across the portfolio. This can create additional considerations around portfolio-level allocation, comparability and coordination, particularly where similar sustainability themes are accessed through different asset classes, investment structures or implementation approaches.

Diversification can be viewed differently under SAA and TPA. Within SAA, climate considerations can be incorporated into long-term capital market assumptions, expected returns, risks and correlations, helping investors assess how climate-related risks and opportunities may influence the efficient frontier and strategic asset allocation over time. Yet, diversification across asset classes does not necessarily imply diversification of sustainability exposures, as different vehicles may remain linked to common underlying sustainability drivers. Diversification is typically evaluated through asset-class characteristics and correlations, while climate-related exposures are managed within individual mandates.

Climate-risk integration, stewardship, decarbonisation, thematic strategies and real assets are commonly implemented within asset-class mandates. Over time, some asset owners have complemented these approaches with a broader portfolio perspective, considering climate solutions, transition finance, resilience and impact-oriented investments across the fund. SAA and TPA are therefore not different generations of sustainable investing. Sustainable-investing practices largely developed through asset-class implementation and continue to play a central role in investment decision-making. As investor objectives have broadened, some asset owners have supplemented these practices with portfolio-level perspectives. The distinction is less about different investments and more about how decisions are framed, compared and governed across the portfolio.

Investment risks

The value of investments and any income will fluctuate (this may partly be the result of exchange rate fluctuations) and investors may not get back the full amount invested. Past performance is not a guide to future returns.