GSS Bonds face a defining moment as reinvestment wall and SFDR 2.0 redraw the market landscape

MainStreet Partners’ latest GSS Bonds Market Trends Report highlights a record reinvestment cycle, the growing strategic role of Green Bonds under SFDR 2.0 and new evidence on the true decarbonisation impact of use-of-proceeds financing.  

• 2025 and 2026 marks the biggest reinvestment pool the market has ever seen
• Green Bonds continue to gain GSS Bond market share – rising to 58% as Social Bonds decline
• Europe’s share of global GSS Bonds issuance continues to decline, falling from 52% in 2021 to 39% in 2025 as Asia’s has more than doubled

Link to full report: GSS Bonds Market Trends Report – January 2026

2025 and 2026 are pivotal periods for the GSS Bonds market, according to MainStreet Partners’ latest edition of the GSS Bonds Market Trends report out today.  

The analysis points to the largest maturity wall the market has faced to date, a potential overhaul of the Sustainable Finance Disclosure Regulation (SFDR 2.0) and increasing scrutiny around how climate impact is measured at project level. Together, these dynamics are reshaping the role of GSS Bonds from a specialist allocation into a more structural component of sustainable portfolios.

Record Reinvestment Cycle Creates Tailwinds for GSS Issuance

According to the report, over EUR 250 billion in GSS Bonds matured in 2025, followed by a further EUR 290 billion in 2026, representing the deepest reinvestment pool the market has ever faced. This returning capital creates favourable conditions for renewed primary market activity, particularly for high-quality Green and Sustainability Bonds.

This maturity wall largely reflects the surge in issuance during 2021, when GSS Bonds volumes peaked and bonds were predominantly issued with five-year tenors.

SFDR 2.0 Positions Green Bonds as a Structural Portfolio Solution

The report places particular emphasis on the implications of the European Commission’s proposed SFDR 2.0 reform. New research from MainStreet Partners research shows how under the framework, a fund may qualify as “Sustainable” or “Transition” with an allocation of around 25% to Green Bonds (with an average EU Taxonomy Alignment of Green Bonds of ~60%). This is enabled by the proposed 15% Taxonomy “Safe Harbour”.

For fixed income and multi-asset strategies, this represents a structural shift. In practical terms, Green Bonds emerge as one of the most efficient and scalable tools for meeting sustainability requirements without compromising portfolio diversification, especially given the constraints around sovereign non-use-of-proceeds instruments.

Issuance-Level Carbon Footprints Reveal Hidden Decarbonisation Impact

Drawing on security-level analysis of more than 3,000 Green and Sustainability Bonds, MainStreet Partners research highlights a difference of 92 tCO₂e per EUR 1 million invested between what is the traditional “issuance-level” carbon footprint and the issuer-level carbon footprint.

This finding challenges the way climate impact is currently measured in bond portfolios. Issuer-level metrics systematically underestimate the decarbonisation impact of use-of-proceeds financing by focusing on an issuer’s balance sheet rather than the projects being financed. Issuance-level analysis, by contrast, provides a more accurate and decision-relevant view of climate impact, in line with the latest guidance from the Partnership for Carbon Accounting Financials (PCAF). 

The report also found that GSS Bond issuance in 2025 topped USD ~1 trillion in 2025, broadly in line with 2023 levels (USD 987bn) and slightly below the USD 1.1trn recorded in 2024.

Green Bonds continued to gain market share within the GSS Bond market and strengthen their position as the largest segment. Their share increases from 53% in 2021 to 58% in 2025. Conversely, over the same period, Social Bonds lost market share, declining from 17% to 13%. Sustainability Bonds saw their market share rise from 19% in 2021 to 26% in 2025. In contrast, the decline in Sustainability-linked Bonds persists, falling to 3% of new issuance in 2025.

Overall, Europe’s share of global GSS issuance has steadily declined, falling from 52% in 2021 to 39% in 2025. Over the same timeframe, Asia more than doubled its share of the market, from 14% to 31%. Supranationals maintain a relatively stable contribution, accounting for around 20% of global issuance in 2025. By contrast, the Americas see a marked reduction in their share, which falls from 16% in 2021 to 8% in 2025.

Pietro Sette, Research Director at MainStreet Partners, commented: “We are entering a new phase where regulation, capital flows, and impact measurement are finally moving in the same direction. For investors who engage early, GSS Bonds are shifting from a niche allocation to a structural portfolio building block. If the SFDR 2.0 proposal were to go ahead as planned, it would materially change the economics of sustainable portfolio construction. Green Bonds will offer one of the most efficient ways to combine regulatory alignment, diversification, and measurable climate impact.”